No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Plant Natural Products Targeting Bacterial Virulence Factors
Abstract
Decreased antimicrobial efficiency has become a global public health issue. The paucity of new antibacterial drugs is evident, and the arsenal against infectious diseases needs to be improved urgently. The selection of plants as a source of prototype compounds is appropriate, since plant species naturally produce a wide range of secondary metabolites that act as a chemical line of defense against microorganisms in the environment. Although traditional approaches to combat microbial infections remain effective, targeting microbial virulence rather than survival seems to be an exciting strategy, since the modulation of virulence factors might lead to a milder evolutionary pressure for the development of resistance. Additionally, anti-infective chemotherapies may be successfully achieved by combining antivirulence and conventional antimicrobials, extending the lifespan of these drugs. This review presents an updated discussion of natural compounds isolated from plants with chemically characterized structures and activity against the major bacterial virulence factors: quorum sensing, bacterial biofilms, bacterial motility, bacterial toxins, bacterial pigments, bacterial enzymes, and bacterial surfactants. Moreover, a critical analysis of the most promising virulence factors is presented, highlighting their potential as targets to attenuate bacterial virulence. The ongoing progress in the field of antivirulence therapy may therefore help to translate this promising concept into real intervention strategies in clinical areas.
... The use of natural compounds in the food industry has been highlighted, both to mitigate the harmful effects of foodborne diseases or in food preservation. In this context, they have been studied for their antimicrobial or even anti-virulence properties as alternatives to antibiotics, food preservatives or chemical disinfectants [13][14][15][16][17][18][19][20][21][22][23][24][25]. Various isolated compounds present in essential oils, herbs, and spices, such as carvacrol, cinnamaldehyde, eugenol and thymol have already shown bactericidal and inhibitory effects on toxin production, quorum sensing, motility and biofilm formation against diverse pathogenic bacteria, including L. monocytogenes [13,15,[24][25][26][27]. ...
... In this context, they have been studied for their antimicrobial or even anti-virulence properties as alternatives to antibiotics, food preservatives or chemical disinfectants [13][14][15][16][17][18][19][20][21][22][23][24][25]. Various isolated compounds present in essential oils, herbs, and spices, such as carvacrol, cinnamaldehyde, eugenol and thymol have already shown bactericidal and inhibitory effects on toxin production, quorum sensing, motility and biofilm formation against diverse pathogenic bacteria, including L. monocytogenes [13,15,[24][25][26][27]. Although some natural compounds have been extensively investigated, there is still a lack of studies concerning their potential as anti-virulence agents or their ability to enhance susceptibility to adverse conditions. ...
... The higher concentration of linalool had the most remarkable reduction in cell survival ( Figure 7B). The lower concentration showed a significant reduction in cell viability but less noticeable in comparison to the previous Antibiotics 2024, 13 Pre-exposure of L. monocytogenes to 0.312 and 0.625 mg/mL of linalool was shown to lead to a significant reduction in the haemolysis of humans' erythrocytes potentially caused by the Listeriolysin O (LLO) of L. monocytogenes, found in the culture supernatant ( Figure 6). The concentration of 0.625 mg/mL showed a significant difference by completely inhibiting the haemolysis of human's erythrocytes (p < 0.00001). ...
Listeria monocytogenes, a foodborne pathogen causing listeriosis, poses substantial societal, economic, and public health challenges due to its resistance, persistence, and biofilm formation in the food industry. Exploring subinhibitory concentrations of compounds to target virulence inhibition and increase susceptibility to adverse conditions presents a promising strategy to mitigate its impact of L. monocytogenes and unveils new potential applications. Thus, this study aims to explore the effect of linalool on virulence factors of L. monocytogenes and potential use in the reduction in its tolerance to stressful conditions. This action was analysed considering the use of two sub-inhibitory concentrations of linalool, 0.312 and 0.625 mg/mL. We found that even with the lowest tested concentrations, a 65% inhibition of violacein production by Chromobacterium violaceum, 55% inhibition in biofilm formation by L. monocytogenes and 62% reduction on haemolysis caused by this bacterium were observed. In addition to its impact on virulence factors, linalool diminished the tolerance to osmotic stress (up to 4.3 log reduction after 24 h with 12% NaCl), as well as to high (up to 3.8 log reduction after 15 min at 55 °C) and low temperatures (up to 4.6 log reduction after 84 days with 12% NaCl at 4 °C). Thus, this study paves the way to further investigation into the potential utilization of linalool to mitigate the threat posed by L. monocytogenes in the field of food safety and public health.
... Se ha propuesto que el desarrollo de terapias antivirulencia puede ser una alternativa viable para combatir infecciones con cepas resistentes, así como evitar su generación (Muñoz-Cazares et al., 2018). El modo de acción de las moléculas antivirulencia se basa en interferir en la producción de los factores que generan el daño al hospedero sin afectar la viabilidad bacteriana (Silva et al., 2016), por lo que se infiere no inducen la aparición de resistencia como los bactericidas clásicos (Rampioni et al., 2014). ...
... Hasta el momento, ha sido en las plantas donde se ha identificado el mayor número de moléculas con esta propiedad, donde los compuestos de naturaleza fenólica son los más abundantes (Asfour, 2017;Hernández-Pasteur et al., 2019;Silva et al., 2016). Para el caso de los denominados fenoles de cadena larga (FCL), sus propiedades bactericidas han sido ampliamente documentadas (Hemshekhar et al., 2012); sin embargo, algunos estudios señalan que también pueden exhibir propiedades antivirulencia, como interferir en la formación de fimbrias (Lee et al., 2014), biopelículas (Jagani et al., 2009) y en la inhibición de sistemas de dos componentes (Kanojia et al., 1999). ...
Las terapias que inhiben la virulencia se han propuesto como una nueva alternativa para combatir infecciones bacterianas debido a que no generan resistencia. Los fenoles de cadena larga producidos por especies de la familia Anacardiaceae estructuralmente son muy diversos y se encuentran en forma de mezclas complejas. El objetivo de esta investigación fue analizar el potencial anti-percepción de quórum de mezclas de fenoles de cadena larga (MFCL) aisladas de dos especies vegetales de importancia etnomedicinal y comercial. Los MFCL se aislaron de la corteza de Amphipterygium adstringens (MFCLAa) y del pericarpo de la nuez de Anacardium occidentale (MFCLAo) con un rendimiento de 0.01 % de cera para MFCLAa y 3.24 % de aceite para MFCLAo. Se identificaron los ácidos anacárdicos como los principales constituyentes mediante espectroscopía de infrarrojo y cromatografía líquida de alta resolución acoplada a espectrometría de masas. En MFCLAa se identificaron las cadenas monoinsaturadas y saturadas de 15 a 19 átomos de carbono C19:1 (41 %) y 15:0 (19.8 %) como las más abundantes. MFCLAo presentó principalmente los compuestos de naturaleza polinsaturada y de cadena de 15 carbonos 15:3 (40 %) y 15:2 (24 %). Ambas mezclas redujeron de manera significativa la producción del pigmento violaceina en el sistema modelo de Chromobacterium violaceum, lo que evidencia una actividad inhibidora de la percepción del quórum. Los dos MFCL evaluados tienen potencial para ser empleados en el desarrollo de terapias de antivirulencia, pero la de A. occidentale tiene la ventaja de producir los compuestos con un mayor rendimiento.
... An alternative approach to affecting bacterial biofilms is antivirulence therapy. Antivirulence compounds are defined as bioactive molecules that interfere with or inhibit virulence factors, including biofilm formation, which is associated with microorganisms' pathogenicity (Fleitas Martínez et al. 2019;Silva et al. 2016). The advantages of this alternative include the ability to weaken the virulence strategies of the microorganisms, making them more susceptible to antibiotics and the immune system's actions. ...
... Additionally, this approach may not exert the same evolutionary pressure as broad-spectrum antibiotics that target essential cellular functions. These therapies may allow the microorganism to maintain its overall fitness and survival without triggering resistance mechanisms by specifically inhibiting virulence factors (Fleitas Martínez et al. 2019;Silva et al. 2016). ...
Staphylococcus aureus is the etiologic agent of many nosocomial infections, and its biofilm is frequently isolated from medical devices. Moreover, the dissemination of multidrug-resistant (MDR) strains from this pathogen, such as methicillin-resistant S. aureus (MRSA) strains, is a worldwide public health issue. The inhibition of biofilm formation can be used as a strategy to weaken bacterial resistance. Taking that into account, we analysed the ability of marine sponge-associated bacteria to produce antibiofilm molecules, and we found that marine Priestia sp., isolated from marine sponge Scopalina sp. collected on the Brazilian coast, secretes proteins that impair biofilm development from S. aureus. Partially purified proteins (PPP) secreted after 24 hours of bacterial growth promoted a 92% biofilm mass reduction and 4.0 µg/dL was the minimum concentration to significantly inhibit biofilm formation. This reduction was visually confirmed by light microscopy and Scanning Electron Microscopy (SEM). Furthermore, biochemical assays showed that the antibiofilm activity of PPP was reduced by ethylenediaminetetraacetic acid (EDTA) and 1,10 phenanthroline (PHEN), while it was stimulated by zinc ions, suggesting an active metallopeptidase in PPP. This result agrees with mass spectrometry (MS) identification, which indicated the presence of a metallopeptidase from the M28 family. Additionally, whole-genome sequencing analysis of Priestia sp. shows that gene ywad, a metallopeptidase-encoding gene, was present. Therefore, the results presented herein indicate that PPP secreted by the marine Priestia sp. can be explored as a potential antibiofilm agent and help to treat chronic infections.
... QS inhibitors have been investigated for their potential to reduce symptoms of infectious diseases (Wang et al., 2016). Three different targets in QS systems can be inhibited: the signal generator, the signal molecule, and the signal receptor (Silva et al., 2016). Although QS inhibitors are very attractive, the complexity of bacterial QS, e.g., multiple regulators and different influences on virulence factor expression, poses a major challenge when comparing QS inhibitors (Silva et al., 2016). ...
... Three different targets in QS systems can be inhibited: the signal generator, the signal molecule, and the signal receptor (Silva et al., 2016). Although QS inhibitors are very attractive, the complexity of bacterial QS, e.g., multiple regulators and different influences on virulence factor expression, poses a major challenge when comparing QS inhibitors (Silva et al., 2016). Our study demonstrated the inhibition of S. aureus QS by geranylated flavonoids through AI-2-mediated bioluminescence in V. harveyi mutant MM30. ...
Ethnopharmacological relevance
Paulownia tomentosa Steud. (P. tomentosa) is a medium-sized tree traditionally used in Chinese folk medicine for the treatment of infectious diseases. It is a rich source of prenylated phenolic compounds that have been extensively studied for their promising biological activities.
Aim of the study
Due to the increasing development of antibiotic resistance, our study investigated plant-derived natural products from the fruits of P. tomentosa that could control Staphylococcus aureus infections with novel targets/modes of action and reduce antimicrobial resistance.
Materials and methods
The ethanolic extract was fractionated and detected by liquid chromatography. The antistaphylococcal effects of the plant formulations were studied in detail in vitro by various biological methods, including microdilution methods for minimum inhibitory concentration (MIC), the checkerboard titration technique for synergy assay, fluorescence measurements for membrane disruption experiments, autoinducer-2-mediated bioassay for quorum sensing inhibition, and counting of colony-forming units for relative adhesion. Morphology was examined by transmission electron microscopy.
Results
Total ethanolic extract and chloroform fraction showed MICs of 128 and 32 μg/ml, respectively. Diplacol, diplacone, and 3′-O-methyl-5′-hydroxydiplacone inhibited S. aureus growth in the range of 8–16 μg/ml. Synergistic potential was shown in combination with mupirocin and fusidic acid. The ethanolic extract and chloroform fraction destroyed cell membranes 91.61% and 79.46%, respectively, while the pure compounds were less active. The ethanolic extract and pure compounds reduced the number of adhered cells to 47.33–10.26% compared to the untreated control. Five tested plant formulations, except diplacone, inhibited quorum sensing of S. aureus. Transmission electron microscopy showed deformation of S. aureus cells.
Conclusions
The products from the fruit of P. tomentosa showed antimicrobial properties against S. aureus alone and in combination with antibiotics. By affecting intracellular targets, geranylated flavonoids proposed novel approaches in the control of staphylococcal infections.
... Natural products have demonstrated different mechanisms of antimicrobial action, such as promoting cell wall rupture and lysis, inhibiting biofilm formation, preventing cell wall construction, interrupting microbial DNA replication, and inhibiting the synthesis of bacterial toxins to the host, among others [5,6]. Furthermore, the remarkable activity of phytochemicals against bacterial virulence factors reinforces the potential of plant natural products in the development of complementary treatments for infectious diseases [7]. The combination of natural products with antibiotics has been recognized as an important strategy to enhance the therapeutic effects of drugs and to limit microbial resistance, mainly by re-sensitizing MDR bacteria to antibiotics, besides preventing the spread of antibiotic resistance [8,9]. ...
... Both Gram-positive and Gram-negative bacteria have the ability to adhere and develop biofilms, but staphylococcal species are most commonly associated with biofilm-related infections, accounting for approximately two-thirds of cases involving indwelling medical devices [28]. Taking this under consideration, and based on the previously observed antimicrobial activity (Table 1), we selected S. aureus, a well-known biofilm-forming strain [7,29], to assess the potential of extracts and phases obtained from M. albicans in preventing biofilm formation ( Fig. 1). The evaluated extracts LEE and SEE did not exhibit any significant activity against biofilm formation. ...
Background
Given the rising occurrence of antibiotic resistance due to the existence and ongoing development of resistant bacteria and phenotypes, the identification of new treatments and sources of antimicrobial agents is of utmost urgency. An important strategy for tackling bacterial resistance involves the utilization of drug combinations, and natural products derived from plants hold significant potential as a rich source of bioactive compounds that can act as effective adjuvants. This study, therefore, aimed to assess the antibacterial potential and the chemical composition of Miconia albicans, a Brazilian medicinal plant used to treat various diseases.
Methods
Ethanolic extracts from leaves and stems of M. albicans were obtained and subsequently partitioned to give the corresponding hexane, chloroform, ethyl acetate, and hydromethanolic phases. All extracts and phases had their chemical constitution investigated by HPLC–DAD-MS/MS and GC–MS and were assessed for their antibiofilm and antimicrobial efficacy against Staphylococcus aureus. Furthermore, their individual effects and synergistic potential in combination with antibiotics were examined against clinical strains of both S. aureus and Acinetobacter baumannii. In addition, 10 isolated compounds were obtained from the leaves phases and used for confirmation of the chemical profiles and for antibacterial assays.
Results
Based on the chemical profile analysis, 32 compounds were successfully or tentatively identified, including gallic and ellagic acid derivatives, flavonol glycosides, triterpenes and pheophorbides. Extracts and phases obtained from the medicinal plant M. albicans demonstrated synergistic effects when combined with the commercial antibiotics ampicillin and ciprofloxacin, against multi-drug resistant bacteria S. aureus and A. baumannii, restoring their antibacterial efficacy. Extracts and phases also exhibited antibiofilm property against S. aureus. Three key compounds commonly found in the samples, namely gallic acid, quercitrin, and corosolic acid, did not exhibit significant antibacterial activity when assessed individually or in combination with antibiotics against clinical bacterial strains.
Conclusions
Our findings reveal that M. albicans exhibits remarkable adjuvant potential for enhancing the effectiveness of antimicrobial drugs against resistant bacteria.
... Например, фенилпропаноиды, такие как эвгенол и коричный альдегид, терпеноиды (тимол и карвакрол), бетулиновая и урсоловая кислоты, алкалоиды, такие как берберин, индол или содержащийся в чистотеле (Chelidonium majus) хелеритрин, и другие соединения растительного происхождения проявляют выраженную активность в отношении биоплёнок, сформированных P. aeruginosa [65][66][67][68][69], K. pneumoniae [70,71] или S. aureus [72][73][74], как растущих, так и уже сформированных. Предполагается, что действие ВМР реализуется различными способами, такими как нарушение коагрегации клеток, ингибирование их подвижности или инактивация бактериальных адгезинов [28,75], а также нарушение межклеточных коммуникаций ("чувства кворума"). Последнее стоит рассмотреть более подробно. ...
Cinchona spp.), который широко известен как эффективное средство против малярии, но использовался также и для лечения других инфекционных заболеваний, таких как пневмония, брюшной тиф и даже обычные инфекции носоглотки [1]. Не менее ярка и драматична история двух других алкалоидов-морфина из опиумного мака (Papaver somniferum), широко использовавшегося в анестезиологии, и атропина из белладонны (Atropa beladonna L.), который нашёл наибольшее применение в офтальмологии. В современном мире вышеупомянутые соединения во многом потеряли свое значение, уступив роль более совершенным препаратам. Однако другие фитопроизводные до сих пор используются в народной медицине, часто как вспомогательные средства в дополнение к рутинной терапии. Более того, некоторые коммерческие лекарственные препараты, применяемые в современной клинической практике, берут начало в традиционной медицине прошлого. Одним из классических примеров является аспирин-производное салициловой кислоты, содержащейся в значительных количествах в вытяжках из коры ивы, которые использовались в древние времена как жаропонижающее и противолихорадочное средство [2, 3]. В число широко известных соединений, полученных из растений и демонстрирующих биологическую активность, в том числе противомикробные свойства, входят, например, аллицин (сероорганическое соединение из Allium spp. подсемейства луковых), пиперин (алкалоид из рода Piper L. семейства перечных), куркумин (Curcuma longa семейства имбирных), эвгенол-основной компонент масла гвоздичного дерева (Syzygium aromaticum, или Eugenia caryophillis), хлорогеновая кислота из плодов кофейного дерева (Coffea L.) и др. [4, 5] Лечебный эффект компонентов растительного сырья обусловлен в значительной мере смесью соединений, которые называют вторичными метаболитами растений (ВМР). ВМР представляют собой разнообразные по химической структуре и свойствам вещества, которые не являются необходимыми для роста и жизнедеятельности растений, но играют важную роль в межвидовой конкуренции или защите от травоядных животных и патогенных микроорганизмов. К настоящему времени идентифицировано около двухсот тысяч ВМР, и есть основания полагать, что это число может быть в разы больше. Многие соединения до сих пор ускользают от внимания исследователей, благодаря очень малому содержанию или короткому времени жизни в изменяющихся условиях окружающей среды [6-8].
... In the last years, compounds of natural origin have shown promising biological effects on certain pathogens; for example, compounds such as 5-hydroxymethylfurfural, chlorogenic acid and ellagic acid are some molecules that have shown multitarget effects on the genes associated with the QS system lasI, lasR, rhlI, rhlR and pqsR and on some virulence genes such as lasB and rhlA, with inhibition percentages between 30 and 70 % for some strains of P. aeruginosa [20][21][22]. It has been widely reported the potential effect of some natural compounds (phenylpropanoids, lignans, terpenes and others) as inhibitors of QS, virulence factors and biofilm on important bacteria in public health [23,24], however, it is necessary to corroborate this GRAPHICAL ABSTRACT effect on the transcripts or proteins of the QS system in order to report the possible potential for different types of structures previously reported to have other biological effects [10,25]. Therefore, the aim of the present study was to determine the possible inhibitory effect of five molecules of natural origin on some genes associated with two pathways of the QS system, as well as on of elastase, protease and pyocyanin production in two resistant strains of P. aeruginosa. ...
... In a preliminary acute toxicity study, supercritical fluid crude extracts were found to have reduced toxicity after SFE optimization combined with extract fractionation. Compounds with a higher mass had higher cytotoxicity related to Caco-2 and HaCaT cells, showing bioactivity or toxicity in a dose-dependent manner [61][62][63][64]. ...
The aim of this review is to discuss the numerous health-promoting properties of Cichorium intybus L. and bring together a range of publications to broaden knowledge and encourage further research and consideration of the plant use as treatment for a range of conditions. A comprehensive search of articles in Polish and English from 1986–2022 years was carried out in PubMed, Google Scholar and ScienceDirect using the keywords chicory, Cichorium intybus L., sesquiterpene lactones and their synonyms. Articles were checked for titles, abstracts, and full-text reviews. The first part of the review article discusses chicory, the countries in which it is found, its life cycle or modern cultivation methods, as well as its many uses, which will be discussed in more detail later in the article. The increased interest in plants as medicines or supplements is also briefly mentioned, as well as some limits that are associated with the medical use of plants. In the Results and Discussion section, there is a discussion of the numerous health-promoting properties of Cichorium intybus L. as a whole plant, with its collection of all the components, and we then examine the structure and the individual constituents of Cichorium intybus L. Among these, this article discusses those that can be utilized for causal applications in medicine, including sesquiterpene lactones and polyphenols, mainly known for their anti-cancer properties, although, in this article, their other health-promoting properties are also discussed. The article also examines inulin, a major component of Cichorium intybus L. The Discussion and the Conclusions sections propose directions for more detailed research and the range of factors that may affect specific results, which may have safety implications when used as supplements or medications.
... Plant species produce a wide range of secondary metabolites that provide a chemical line of defense against environmental microorganisms. Many phytochemicals have been identified that modulate the production of bacterial virulence factors and have potential to become lead compounds in research on anti-virulence therapy (Silva et al., 2016). Physalins, or 16,24-cyclo-13,14-seco steroids, belong to the class of withanolides that exhibit promising pharmacological properties (Wu et al., 2021;Yang et al., 2022). ...
The virulence of Staphylococcus aureus, including methicillin-resistant S. aureus (MRSA), depends on the expression of toxins and virulence factors controlled by the quorum-sensing (QS) system, encoded on the virulence accessory gene regulator (agr) locus. The aim of this study was to identify a phytochemical that inhibits Agr-QS function and to elucidate its mechanism. We screened 577 compounds and identified physalin H, physalin B, and isophysalin B—–phytochemicals belonging to physalins found in plants of the Solanaceae family—–as novel Agr-QS modulators. Biological analyses and in vitro protein–DNA binding assays suggested that these physalins suppress gene expression related to the Agr-QS system by inhibiting binding of the key response regulator AgrA to the agr promoters, reducing the function of hemolytic toxins downstream of these genes in MRSA. Furthermore, although physalin F suppressed gene expression in the Agr-QS system, its anti-hemolytic activity was lower than that of physalins H, B, and isophysalin B. Conversely, five physalins isolated from the same plant with the ability to suppress Agr-QS did not reduce bacterial Agr-QS activity but inhibited AgrA binding to DNA in vitro. A docking simulation revealed that physalin interacts with the DNA-binding site of AgrA in three docking states. The carbonyl oxygens at C-1 and C-18 of physalins, which can suppress Agr-QS, were directed to residues N201 and R198 of AgrA, respectively, whereas these carbonyl oxygens of physalins, without Agr-QS suppression activity, were oriented in different directions. Next, 100-ns molecular dynamics simulations revealed that the hydrogen bond formed between the carbonyl oxygen at C-15 of physalins and L186 of AgrA functions as an anchor, sustaining the interaction between the carbonyl oxygen at C-1 of physalins and N201 of AgrA. Thus, these results suggest that physalin H, physalin B, and isophysalin B inhibit the interaction of AgrA with the agr promoters by binding to the DNA-binding site of AgrA, suppressing the Agr-QS function of S. aureus. Physalins that suppress the Agr-QS function are proposed as potential lead compounds in the anti-virulence strategy for MRSA infections.
... Antivirulence chemicals can enhance the safety and therapeutic efficacy of antibiotics if used in combination [10]. Many polyphenolic compounds originating from plants, such as flavonoids and phenolic acids, exhibit antimicrobial action against a wide variety of pathogens and offer practical antibacterial weapons for natural warfare. ...
Methicillin-resistant Staphylococcus aureus (MRSA) is a common resistant bacterium, whose resistance has expanded to commonly used antibiotics. It is crucial to create novel treatments to tackle bacterial resistance. Trans-resveratrol and curcumin are naturally occurring phenolic compounds, whose effects on MRSA virulence are the subject of this investigation. Sub-MICs of trans-resveratrol and curcumin were tested on the virulence factors of 50 MRSA clinical isolates (CIs), including biofilm, hemolysin, hemagglutination, protease, and lecithinase. The distribution of the virulence factors of the CIs was as follows: hemolysin: 98%, hemagglutination: 70%, protease: 62%, biofilm: 56%, and lecithinase: 52%. The sub-MIC that could reduce the effect of the tested virulence factors by 50% or more (IC50) was observed in the strains that showed susceptibility to the individual administration of trans-resveratrol at 50 µg/mL and curcumin at 20 µg/mL. Hemagglutination and hemolysin activity were inhibited by at least 50% in the majority of CIs (57–94%). Meanwhile, the IC50 for protease and biofilm was observed in 6.5–17.8% of the CIs. A few of the CIs were susceptible to lecithinase inhibition, but all showed a full inhibition. This research supports the possibility of the use of these compounds to reduce the bacterial virulence that can reduce antibiotic utilization, and eventually, they can become a potential alternative treatment in combating bacterial resistance.
... Numerous studies have highlighted that plant-derived chemicals exhibit additional biofunctions, making them potential candidates with antibacterial or antibiofilm properties, which is an intriguing approach. Various plants, such as Aloe vera, Chamomile (Chamaemelum nobile), and Garlic (Allium sativum L.), have been utilized for their therapeutic properties (Silva et al. 2016). Contemporary advancements in science and technology are accelerating the discovery and development of new drugs that exhibit enhanced therapeutic activity while minimizing side effects. ...
Various bacterial pathotypes remain a significant public health concern due to their pathogenicity and antimicrobial resistance. Moreover, the ability of bacteria to form biofilms can hinder host defense and antimicrobial eradication, leading to additional resistance. This study aimed to estimate the cinnamic acid's anti-biofilm activity against biofilms-producing bacteria. From October to November 2023, various clinical isolates were obtained from the Bacteriology Unit, Ramadi Teaching Hospital, Iraq. All isolates were identified using a conventional and automated VITEK-2 compact system. Based on the Clinical and Laboratory Standards Institute (CLSI) guidelines and the European Committee on Antimicrobial Susceptibility Testing (EUCAST), the Kirby- Bauer disk diffusion and AST were performed for antimicrobial susceptibility. Biofilm formation was estimated using a 96-well Enzyme-linked immunosorbent assay (ELISA) reader. Based on the antimicrobial susceptibility test, all bacterial isolates showed antibiotic resistance, including Kleibsella pneumonieae, Psuedomonas aeruginosa, Escherichia coli and Staphylococcus aureus. The data showed that MICs of cinnamic acid against bacteria were 125 μg /ml.The biofilms formed by all isolates exhibited strong strength (OD570 : 0.078-0.099). Cinnamic acid demonstrated significant inhibition of biofilm production in Multidrug resistance (MDR) bacteria (P-value = 0.0236). The results indicated that Cinnamic acid could be a promising anti-infective agent based on its ability to inhibit MDR-bacterial infections through biofilm formation.
... Previously, natural compounds isolated from plant naturals have shown a target bacterial virulence factor. 25 The effects of polyphenolic compounds and derivatives on strains of S. aureus and S. pneumoniae are promising. These bacteria are known to harbor toxins, such as hemolysin, which is a pore-forming toxin similar to ily. 26 In the present study, kale inhibited the expression of the ily gene dose-dependently. ...
Persistent odontogenic infections caused by resistant bacterial species, such as , have consistently been associated with deep-seated infections. This in vitro study aimed to evaluate the antibacterial and antivirulence effects of kale () on .
was freshly incubated in tryptic soy broth media. Three experiments per concentration of kale were conducted under aseptic conditions (i.e., disc diffusion, broth microdilution, and reverse-transcription polymerase chain reaction) to evaluate the antibacterial and antivirulence effects. The samples were then treated with 1000, 500, 250, 125, 65, 30, 15, 7, and 3 mg/mL kale; ampicillin (positive control); and tryptic soy broth (negative control). After 24-h incubation, the inhibition zone, minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and relative gene expression of the virulence factor (intermedilysin []) were measured. All assays were conducted in triplicate. The findings were reported and analyzed as means ± standard deviations. The agar disc diffusion and relative gene expression were statistically analyzed using one-way analysis of variance and Tukey’s test, with the significance level set at P < 0.05.
Kale showed antibacterial effects on by significantly inhibiting bacterial growth and reducing expression only at a concentration of 1000 mg/mL; it yielded an inhibition zone of 11.12 ± 1.59 mm, which was smaller than that with ampicillin. The MIC and MBC ranged from 15 to 65 mg/mL and from 500 mg/mL, respectively. Conversely, the highest concentration of kale yielded significantly less inhibition than did ampicillin.
The antibacterial effects of kale may be dose-dependent. Kale can inhibit bacterial growth and suppress expression under in vitro conditions of , which is mainly involved in deep-seated odontogenic infections.
... Carvacrol and thymol, active ingredients of the Lamiaceae family plants have been used for curbing antimicrobial resistant gram-positive and negative isolates of bacteria [22]. Natural products have also been used to target quorum sensing, bacterial motility, and enzymatic activity [23]. However, despite these remarkable discoveries, the specific investigation of natural products against Ef-Tu as a drug target has been conspicuously lacking, leaving a significant gap in our understanding and exploration of their potential in this context. ...
The oral pathogen Fusobacterium nucleatum has recently been associated with an elevated risk of colorectal cancer (CRC), endometrial metastasis, chemoresistance, inflammation, metastasis, and DNA damage, along with several other diseases. This study aimed to explore the disruption of protein machinery of F. nucleatum via inhibition of elongation factor thermo unstable (Ef-Tu) protein, through natural products. No study on Ef-Tu inhibition by natural products or in Fusobacterium spp. exists till todate. Ef-Tu is an abundant specialized drug target in bacteria that varies from human Ef-Tu. Elfamycins target Ef-Tu and hence, Enacyloxin IIa was used to generate pharmacophore for virtual screening of three natural product libraries, Natural Product Activity and Species Source (NPASS) (n = 30000 molecules), Tibetan medicinal plant database (n = 54 molecules) and African medicinal plant database (n > 6000 molecules). Peptaibol Septocylindrin B (NPC141050), Hirtusneanoside, and ZINC95486259 were prioritized from these libraries as potential therapeutic candidates. ADMET profiling was done for safety assessment, physiological-based pharmacokinetic modeling in human and mouse for getting insight into drug interaction with body tissues and molecular dynamics was used to assess stability of the best hit NPC141050 (Septocylindrin B). Based on the promising results, we propose further in vitro, in vivo and pharmacokinetic testing on the lead Septocylindrin B, for possible translation into therapeutic interventions.
... For instance, they interact with bacterial cell wall structures and proteins, reduce the fluidity of the membrane, damage cytoplasmic membranes, inhibit cell wall and nucleic acid synthesis and hamper energy metabolism [65]. Research on the antibiofilm potential of plant phenolics has revealed that these agents cause biofilm suppression by changing bacterial regulatory mechanisms like quorum sensing (QS) or other systems of global regulators, without affecting the growth of bacteria [66]. Research published on antibiofilm potentials of flavonoids, tannins and phenolic acids is summarized in Table 3. ...
The emergence of multidrug-resistant (MDR) pathogens is a major problem in the therapeutic management of infectious diseases. Among the bacterial resistance mechanisms is the development of an enveloped protein and polysaccharide-hydrated matrix called a biofilm. Polyphenolics have demonstrated beneficial antibacterial effects. Phenolic compounds mediate their antibiofilm effects via disruption of the bacterial membrane, deprivation of substrate, protein binding, binding to adhesion complex, viral fusion blockage and interactions with eukaryotic DNA. However, these compounds have limitations of chemical instability, low bioavailability, poor water solubility and short half-lives. Nanoformulations offer a promising solution to overcome these challenges by enhancing their antibacterial potential. This review summarizes the antibiofilm role of polyphenolics, their underlying mechanisms and their potential role as resistance-modifying agents.
... Phenolic acids and flavonoids have been reported to show potent antibiofilm activity against P. aeruginosa through the reduction of quorum sensing-regulated gene transcription (Silva et al., 2016). Recently, flavonols represented by rutin, kaempferol, and quercetin exerted significant inhibition against the biofilm formation of K. pneumoniae (Wang et al., 2021). ...
In recent decades, the concept of sustainability has gained significant popularity, with a great emphasis on revalorizing agro-byproducts as potential sources of bioactive compounds. Radish and turnip are economically significant crops that are widely produced across the world for direct consumption or oil and condiment production. Additionally, they are also frequently used in traditional medicine to cure bacterial infections, becoming a potential source of antimicrobial and antivirulence agents to combat microbial resistance. Here, a comprehensive metabolite fingerprinting was adopted to characterize the leaves and roots of three varieties of radish (Daikon, white icicle, and red radish) and turnip concerning their antibacterial and antivirulence activities. A total of 120 metabolites from various classes were annotated using liquid chromatography-quadrupole time-of-flight-tandem mass spectrometry (LC-QTOF-MS/MS) and molecular networking. Multivariate data analysis revealed that metabolites distribution and abundance differed between samples, with glucosinolates, flavonoids, phenolic, and fatty acids being the most significantly differential metabolites. Whereas daikon and turnip leaves were enriched in flavonoids and glucosinolates, red radish and turnip leaves were high in phenolic acids, and red radish roots were high in fatty acids. All extracts exhibited significant antibacterial activity against K. pneumoniae and P. aeruginosa. Daikon and turnip leaves prevented biofilm formation in K. pneumoniae by 99.7 % and 74.2 %, respectively, whereas white icicle, turnip, and daikon roots inhibited biofilm formation in P. aeruginosa by 69.7 %, 67.0 %, and 62.2 %, respectively. The roots of white icicle and red radish reduced P. aeruginosa swarming motility by 83.1 % and 83.3 %, respectively, whereas the roots of white icicle, daikon, and red radish reduced its swimming motility by 84.4 %, 82.5 %, and 82.4 %, respectively. Additionally, the leaves of white icicle radish inhibited pyocyanin production in P. aeruginosa by 76.8 %. Pearson's correlation analyses revealed that the bioactivities were linked to various phenolic and sulfur compounds. The current study is the first to combine List of Abbreviations: cv, culture variety; DL, daikon leaf; DR, daikon root; ESI, electrospray ionization; GNPS-MN, Global natural products social molecular networking; LC-MS/MS, liquid chromatography-tandem mass spectrometry; LC-QTOF-MS/MS, liquid chromatography-quadrupole time-of-flight tandem mass 2 metabolomics, molecular networking, and chemometrics approaches to unveil metabolome heterogeneity among radish and turnip leaves and roots, which could be derived from agro-byproducts to revalorize while validating their potential as promising sources of antivirulence phytochemicals.
... This capacity could enable these natural antibacterials to activate different modes of action in comparison to conventional antibacterial agents, thereby helping to reduce microbial resistance [23]. ...
Streptococcus mutans (S. mutans) is the main cariogenic bacterium with acidophilic properties, in part due to its acid-producing and -resistant properties. As a result of this activity, hard tooth structures may demineralize and form caries. Trans-cinnamaldehyde (TC) is a phytochemical from the cinnamon plant that has established antibacterial properties for Gram-positive and -negative bacteria. This research sought to assess the antibacterial and antibiofilm effects of trans-cinnamaldehyde on S. mutans. TC was diluted to a concentration range of 156.25–5000 μg/mL in dimethyl sulfoxide (DMSO) 0.03–1%, an organic solvent. Antibacterial activity was monitored by testing the range of TC concentrations on 24 h planktonic growth compared with untreated S. mutans. The subminimal bactericidal concentrations (MBCs) were used to evaluate the bacterial distribution and morphology in the biofilms. Our in vitro data established a TC MBC of 2500 μg/mL against planktonic S. mutans using a microplate spectrophotometer. Furthermore, the DMSO-only controls showed no antibacterial effect against planktonic S. mutans. Next, the sub-MBC doses exhibited antibiofilm action at TC doses of ≥625 μg/mL on hydroxyapatite discs, as demonstrated through biofilm analysis using spinning-disk confocal microscopy (SDCM) and high-resolution scanning electron microscopy (HR-SEM). Our findings show that TC possesses potent antibacterial and antibiofilm properties against S. mutans. Our data insinuate that the most effective sub-MBC of TC to bestow these activities is 625 μg/mL.
... Although conventional strategies aimed at reducing microbial infections are efficacious, targeting virulence factors rather than their survival and growth appears to be an attractive approach. This approach may lead to reduced pathogenicity of pathogens and a reduction in the development of resistance (Silva et al., 2016). Indeed, the ability of a pathogenic bacterium to form biofilm communities and to move across surfaces is very important for virulence determination (Kearns, 2010;Rajkumari et al., 2018b). ...
The phytoconstituents of the aqueous extract from Syzygium jambos L. (Alston) leaves were defined using HPLC-PDA-MS/MS and the antioxidant, anti-aging, antibacterial, and anti-biofilm activities of the extract were in silico and in vitro investigated. The antioxidant activities were performed using in vitro DPPH and FRAP assays as well as H2-DCFDA assay in HaCaT cells in which oxidative stress was induced by UVA radiation. Anti-aging activity was tested in vitro, using aging-related enzymes. The antibacterial, anti-biofilm and inhibitory effects on bacterial mobilities (swarming and swimming) were assessed against Pseudomonas aeruginosa. Results showed that S. jambos aqueous extract contained 28 phytochemicals belonging to different metabolite classes, mainly phenolic acids, gallic acid derivatives, flavonoids, and ellagitannins. Mineral content analysis showed that S. jambos leaves contained moderate amounts of nitrogen, potassium, manganese, magnesium, and zinc, relatively low amounts of phosphorus and copper, and high concentration of calcium and iron. The extract displayed strong antioxidant activities in vitro and inhibited UVA-induced oxidative stress in HaCaT cells. Docking the major compounds identified in the extract into the four main protein targets involved in skin aging revealed an appreciable inhibitory potential of these compounds against tyrosinase, elastase, hyaluronidase, and collagenase enzymes. Moreover, molecular dynamic simulations were adopted to confirm the binding affinity of some selected compounds towards the target enzymes. The extract exhibited pronounced in vitro anti-aging effects, compared to kojic acid and quercetin (the reference compounds). It also inhibited the growth of P. aeruginosa, counteracted its ability to form biofilm, and impeded its swarming and swimming mobilities. Altogether, these findings strongly propose S. jambos leaves as a promising source of bioactive metabolites for the development of natural cosmeceutical and dermatological agents.
... Например, фенилпропаноиды, такие как эвгенол и коричный альдегид, терпеноиды (тимол и карвакрол), бетулиновая и урсоловая кислоты, алкалоиды, такие как берберин, индол или содержащийся в чистотеле (Chelidonium majus) хелеритрин, и другие соединения растительного происхождения проявляют выраженную активность в отношении биоплёнок, сформированных P. aeruginosa [65][66][67][68][69], K. pneumoniae [70,71] или S. aureus [72][73][74], как растущих, так и уже сформированных. Предполагается, что действие ВМР реализуется различными способами, такими как нарушение коагрегации клеток, ингибирование их подвижности или инактивация бактериальных адгезинов [28,75], а также нарушение межклеточных коммуникаций ("чувства кворума"). Последнее стоит рассмотреть более подробно. ...
Bacterial infections are a serious cause of high morbidity and mortality worldwide. Over the past decades, the drug resistance of bacterial pathogens has been steadily increasing, while the rate of development of new effective antibacterial drugs remains consistently low. The plant kingdom is sometimes called a bottomless well for the search for new antimicrobial therapies. This is due to the fact that plants are easily accessible and cheap to process, while extracts and components of plant origin often demonstrate a high level of biological activity with minor side effects. The variety of compounds obtained from plant raw materials can provide a wide choice of various chemical structures for interaction with various targets inside bacterial cells, while the rapid development of modern biotechnological tools opens the way to the targeted production of bioactive components with desired properties. The objective of this review is to answer the question, whether antimicrobials of plant origin have a chance to play the role of a panacea in the fight against infectious diseases in the “post-antibiotic era”.
... Although conventional strategies aimed at reducing microbial infections are efficacious, targeting virulence factors rather than their survival and growth appears to be an attractive approach. This approach may lead to reduced pathogenicity of pathogens and a reduction in the development of resistance (Silva et al., 2016). Indeed, the ability of a pathogenic bacterium to form biofilm communities and to move across surfaces is very important for virulence determination (Kearns, 2010;Rajkumari et al., 2018b). ...
The phytoconstituents of the aqueous extract from Syzygium jambos L. (Alston) leaves were defined using HPLC-PDA-MS/MS and the antioxidant, anti-aging, antibacterial, and antibiofilm activities of the extract were in silico and in vitro investigated. The antioxidant activities were performed using in vitro DPPH and FRAP assays as well as H2-DCFDA assay in HaCaT cells in which oxidative stress was induced by UVA radiation. Anti-aging activity was tested in vitro, using aging-related enzymes. The antibacterial, anti-biofilm and inhibitory effects on bacterial mobilities (swarming and swimming) were assessed against P. aeruginosa. Results showed that S. jambos aqueous extract contained 28 phytochemicals belonging to different metabolite classes, mainly phenolic acids, gallic acid derivatives, flavonoids, and ellagitannins.Mineral content analysis showed that S. jambos leaves contained moderate amounts of nitrogen, potassium, manganese, magnesium, and zinc, relatively low amounts of phosphorus and copper, and high concentration of calcium and iron. The extract displayed strong antioxidant activities in vitro and inhibited UVA-induced oxidative stress in HaCaT cells. Docking the major compounds identified in the extract into the four main protein targets involved in skin aging revealed an appreciable inhibitory potential of these compounds against tyrosinase, elastase, hyaluronidase, and collagenase enzymes. Moreover, molecular dynamic simulations were adopted to confirm the binding affinity of some selected compounds towards the target enzymes. The extract exhibited pronounced in vitro anti-aging effects, compared to kojic acid and quercetin (the reference compounds). It also inhibited the growth of P. aeruginosa, counteracted its ability to form biofilm, and impeded its swarming and swimming mobilities. Altogether, these findings strongly propose S. jambos leaves as a promising source of bioactive metabolites for the development of natural cosmeceutical and dermatological agents.
... In this regard, some natural antimicrobials like essential oils (thymol, carvacrol, eugenol), as secondary metabolites of some plants, have promising antibacterial/antibiofilm activity against a wide range of Gramnegative and Gram-positive bacteria (Nazzaro et al. 2013 ), and such agents are reported to have less side effects, compared to other conventional therapies, in cells and whole animals (Puglia and Santonocito 2019 ). These metabolites have gained much interest as alternatives to antibiotics for their broad-spectrum antibacterial potency, multiple mechanisms of action, and low tendency to induce resistance (Silva et al. 2016 ). However, their clinical application has been greatly limited due to their poor aqueous solubility. ...
Aims
The purpose of this study was to synthesize a nanoform of eugenol (an important phytochemical with various pharmacological potentials) and to investigate its anti-biofilm efficacy on Pseudomonas aeruginosa biofilm.
Methods and results
Colloidal suspension of eugenol-nanoparticles (ENPs) was synthesized by the simple ultrasonic cavitation method through emulsification of hydrophobic eugenol into hydrophilic gelatin. Thus, the nanonization process made water-insoluble eugenol into water-soluble nano-eugenol, making the nano-form bioavailable. The size of the ENPs was 20–30 nm, entrapment efficiency of eugenol within gelatin was 80% and release of eugenol from gelatin cap was slow and sustained over five-days. Concerning the clinically relevant pathogen Pseudomonas aeruginosa, ENP had higher anti-biofilm (for both formation and eradication) activities than free eugenol. Minimal biofilm inhibitory concentration and minimal biofilm eradication concentration of ENP on P. aeruginosa biofilm were 2.0 and 4.0 mM respectively. In addition, the measurement of P. aeruginosa biofilm biomass, biofilm thickness, amount of biofilm extra-polymeric substance, cell surface hydrophobicity, cell swarming and twitching efficiencies, cellular morphology and biofilm formation in catheter demonstrated that the anti-biofilm efficacy of nano-eugenol was 30–40% higher than that of bulk eugenol.
Conclusion
These results signify that future pharmacological and clinical studies are very much required to investigate whether ENP can act as an effective drug against P. aeruginosa biofilm-mediated diseases. Thus, the problem of intrinsic antibiotics-tolerance of biofilm-forming cells may be minimized by ENP. Moreover, ENP may be used as a potential catheter-coating agent to inhibit pseudomonal colonization on catheter surfaces and therefore, to reduce catheter-associated infections and complications.
... In addition, some studies have proven that some spice essential oils and their bioactive compounds can affect biofilm formation by interfering with the initial adherence step of planktonic cells (Silva et al., 2016), downregulating fimbriae gene expression or even reducing extracellular polymeric substance production (Kim et al., 2016;Zhang et al., 2020). Nevertheless, the exact effect of FO on virulence factors in S. maltophila or any other bacteria was not explained before, so further studies are needed to explain the anti-virulence effects detected in this study and highlight the main components of the oil that provided these effects and the proposed mechanisms. ...
Stenotrophomonas maltophilia is a gram-negative opportunistic pathogenic bacterium that is associated with hospital- and community-acquired infections. It has a set of virulence factors, such as biofilm formation and extracellular enzymes, that are mostly regulated via quorum sensing (QS) systems. Azithromycin (AZM) is a macrolide that is well known for its anti-virulence effects, including anti-QS and antibiofilm effects. Additionally, some spice essential oils have been reported to inhibit bacterial virulence. This study evaluated the effect of AZM and Fenugreek Oil (FO), a spice essential oil from Fenugreek seeds, against some virulence factors of multidrug-resistant Stenotrophomonas maltophilia clinical isolates. Both AZM and FO showed significant inhibitory effects against protease activity, where all tested isolates showed 100% loss of the halo zone formed in skimmed milk agar test with AZM and a 25 to 35% reduction in the zone with FO. A mean reduction in the interstitial surface area of 34.4% and 35.5% was detected with AZM and FO, respectively, in the twitching motility assay. While AZM showed a significant effect in reducing biofilm formation by S. maltophilia isolates (mean inhibition of 49.7%), the reducing effect of FO (18.5%) was not significant. Genotypically, exposure of S. maltophilia clinical isolates to AZM and FO significantly reduced the expression of protease-encoding genes (stmPr1, stmPr2 and StmPr3) and a quorum sensing gene (rpfC).
... In addition, B. cereus is a multifaceted opportunistic pathogen (Messelhäußer and Ehling-Schulz, 2018), and it can produce a toxin called "Cereulide" that cannot be removed during food production and processing (Rouzeau-Szynalski et al., 2020;Yang et al., 2023), thereby leading to food poisoning and causing some symptoms such as foodborne gastroenteritis, vomiting, and diarrhea (Chen et al., 2019;Thirkell et al., 2019). Moreover, the virulence factors of toxin-producing B. cereus still include cytotoxin K, cephalin, metalloproteinase, sphingomyelin, and phospholipase (Silva et al., 2016;Enosi Tuipulotu et al., 2021). Therefore, B. cereus is also considered a non-environmentally polluting pathogenic bacterium with potential lethality (Leung et al., 2019;Wu et al., 2019). ...
... It disrupt normal metabolism in bacteria mainly by affecting microbial metabolism in diverse environments, and energy metabolism including carbon metabolism, glyoxylate and dicarboxylate metabolism and fructose and mannose metabolism, and affected bacterial secretion systems and quorum sensing significantly (Li et al., 2022). Quorum sensing is a chemical communication system in which bacterial pathogens express certain virulence genes at high cell densities and communicate with each other by small diffusible signalling molecules called selfinducers (Silva et al., 2016). ...
In most developing countries, rainwater is used by many people to meet their water needs. Many Bacillus species known to be harmful to humans have also been identified in rainwater samples. Improving the microbiological quality of the rainwater using modern techniques seems expensive in rural areas for poor people. Extracts from several medicinal plants are often used in rural areas to treat certain bacterial infections. Water and alcohol are often used in traditional therapy to extract the principles of medicinal plants. But little is known about their functional differences or similarities. This study aims to assess the effects of aqueous and hydro-ethanolic leaf extracts of Moringa oleifera Lam on the cultivability of Bacillus cereus and Bacillus thuringiensis isolated from rainwater. Leaf extracts of concentrations 2, 1.5, 1 and 0.5 g/L in contact with cells were incubated at 23°C and 37°C for 3 h, 6 h, 9 h and 24 h. The results showed a decrease in cultivable cells abundance. In most cases, cell abundances between the aqueous extract and hydro-ethanolic extract were not significantly different (P>0.05). A significant difference (P<0.05) was noted amongst cell abundances from each incubation period to another. The effectiveness of each extract for cell inhibition was evaluated and then expressed as a decrease percentage in the number of cultivable cells. A decrease in cultivable B. thuringiensis abundance varied from 75.09 to 99.68% in hydro-ethanolic extract and from 70.75 to 97.94% in aqueous extract. That of B. cereus varied from 0 to 98.86% in hydro-ethanolic extract and from 41.09 to 92.20% in the other. This difference could be linked to the differences in the cell species intrinsic properties. It could also be linked to the presence of some compounds identified. Some of these compounds would act as nutrients for cell growth, counterbalancing cell inhibition caused by others that have antimicrobial effects. Practical application M. oleifera leaves extract could nevertheless be exploited as an alternative to the microbiological treatment of rainwater, mainly against B. thuringiensis in particular, for household use in rural areas. However, further work is essential to clarify the effective constituents inactivating bacteria in the extracts, their potential impact on the water organoleptic properties as well as on human health.
... During plant infection, pathogenic bacteria secrete and release virulence factors, which play a decisive role during the infection process (Gellatly and Hancock, 2013;Newman et al., 2017). The primary bacterial virulence factors include quorum sensing, biofilm, motility, toxins, and pigment (Poole, 2011;Silva et al., 2016). Bacterial pigments with distinctive chemical structures, serving as virulence factors for pathogenic bacteria, actively contribute to the onset of host diseases by subverting clearance by the host immune response or demonstrating the capability to stimulate an inflammatory response or cellular toxicity (Liu and Nizet, 2009). ...
Bacterial pigment is one of the secondary metabolites produced by bacteria and has functions that are yet to be understood in relation to soil-borne pathogenic fungi and plants in mutualistic processes. The study evaluates the growth, photosynthetic, and physiological characteristics of alfalfa after interacting with different concentrations of Cp2 pink pigment and Fusarium chlamydosporum . The findings showed that Cp2 pink pigment has the ability to inhibit the growth of alfalfa, with the inhibition ratio gradually increasing with rising concentration. F. chlamydosporum inhibited the growth of alfalfa, which reduced the photosynthetic physiological response and elevated antioxidant enzymes, which are typically manifested by yellowing leaves and shortened roots. Under the combined effect of Cp2 pink pigment and F. chlamydosporum , increasing concentrations of Cp2 pink pigment intensified the symptoms in alfalfa and led to more pronounced growth and physiological response. This indicates that the Cp2 pink pigment is one of the potential virulence factors secreted by the Erwinia persicina strain Cp2, which plays an inhibitory role in the interactions between F. chlamydosporum and alfalfa, and also has the potential to be developed into a plant immunomodulator agent.
Controlling the growth of microbial consortia is of great significance in the biomedical field. Selective bacterial growth was achieved by fabricating silk inverse opal (SIO) scaffolds with varying pore sizes ranging from 0.3 μm to 4.5 μm. Pore size significantly influences the growth dynamics of bacteria in both single and mixed‐strain cultures. Specially, the SIO‐4.5 μm scaffold was observed to be more favorable for cultivating S. aureus , whereas the SIO‐0.3 μm scaffold was more suitable for cultivating E. coli and P. aeruginosa . By adjusting the secondary conformation of silk fibroin, the stiffness of the SIO substrate will be altered, which resulted in the increase of bacteria on the SIO by 16 times compared with that on the silk fibroin film(SFF). Manipulating the pore size allows for the adjustment of the S. aureus to P. aeruginosa ratio from 0.8 to 9.3, highlighting the potential of this approach in regulating bacterial culture.
This article is protected by copyright. All rights reserved
Flavonoids are an important class of natural compounds with a broad spectrum of biological activities, which makes them interesting candidates for pharmaceutical applications. The current demand for novel compounds to control the bacterial infections has spurred a growing interest in antivirulence agents. Instead of inhibiting bacterial growth or killing pathogens, as classical antibacterials, these agents modulate bacterial virulence, disrupting the production or blocking virulence determinants that are essential for pathogenesis. Extensive research has been done on the structure–activity relationship of antibacterial glycosylated flavonoids and their respective aglycones. Glycosylation, particularly at the C-7 position of the main structure, is known to reduce the antibacterial activity of flavonoids. However, the impact of glycosylation on the antivirulence activity of flavonoids remains inadequately explored. This review addresses 54 glycosylated flavonoids and their effects on bacterial growth and virulence factors, including biofilms, motility, toxins, enzymes, pigments, and chemical communication systems. Although a relatively low number of correlation studies between the structure of flavonoids and antivirulence activities are available in literature, it is possible to infer that, in general, glycosylation negatively affects antivirulence property, similarly to what is documented for antibacterial activity. Sugar substituents at position C-7 have shown to also decrease antibiofilm action, and flavonoid neohesperidosides are more effective than rutinosides. Additionally, the position of glycosylation affects the antivirulence activity, especially in quorum sensing bacterial chemical communication system. However, synergistic effects of glycosylated flavonoids, especially flavanol-3-O-glycosides, with β-lactams and quinolones, are observed that suggest their potential use as adjuvants in antimicrobial therapy. The findings highlighted by this review are useful for the search, design, and development of new therapeutic alternatives to control bacterial infections.
This review covers the most recent advances in the development of inhibitors for the bacterial enzyme sortase A (SrtA). Sortase A (SrtA) is a critical virulence factor, present ubiquitously in Gram‐positive bacteria of which many are pathogenic. Sortases are key enzymes regulating bacterial adherence to host cells, by anchoring extracellular matrix‐binding proteins to the bacterial outer cell wall. By targeting virulence factors, effective treatment can be achieved, without inducing antibiotic resistance to the treatment. This is a potentially more sustainable, long‐term approach to treating bacterial infections, including ones that display multiple resistance to current therapeutics. There are many promising approaches available for SrtA inhibition, some of which have the potential to advance into further clinical development, with peptidomimetic and in vivo active small molecules being among the most promising. There are currently no approved drugs on the market targeting SrtA, despite its promise, adding to the relevance of this review article, as it extends to the pharmaceutical industry additionally to academic researchers.
Methylrhodomelol (1) is a bromophenol from the red alga Vertebrata lanosa that has been associated with antimicrobial properties. The aim of the current study was, therefore, to assess the antimicrobial potential of this compound in more detail against the gram-negative pathogen Pseudomonas aeruginosa. 1 exerted weak bacteriostatic activity against different strains when grown in minimal medium, whereas other phenolics were inactive. In addition, 1 (35 and 10 µg/mL) markedly enhanced the susceptibility of multidrug-resistant P. aeruginosa toward the aminoglycoside gentamicin, while it did not affect the viability of Vero kidney cells up to 100 µM. Finally, pyoverdine release was reduced in bacteria treated at sub-inhibitory concentration, but no effect on other virulence factors was observed. Transcriptome analysis of treated versus untreated P. aeruginosa indicated an interference of 1 with bacterial carbon and energy metabolism, which was corroborated by RT-qPCR and decreased ATP-levels in treated bacteria. In summary, the current study characterized the antibacterial properties of methylrhodomelol, revealed its potential as an adjuvant to standard antibiotics, and generated a hypothesis on its mode of action.
This study introduces a tyrosol-loaded niosome integrated into a chitosan–alginate scaffold (Nio-Tyro@CS-AL), employing advanced electrospinning and 3D printing techniques for wound healing applications. The niosomes, measuring 185.40 ± 6.40 nm with a polydispersity index of 0.168 ± 0.012, encapsulated tyrosol with an efficiency of 77.54 ± 1.25%. The scaffold’s microsized porous structure (600–900 μm) enhances water absorption, promoting cell adhesion, migration, and proliferation. Mechanical property assessments revealed the scaffold’s enhanced resilience, with niosomes increasing the compressive strength, modulus, and strain to failure, indicative of its suitability for wound healing. Controlled tyrosol release was demonstrated in vitro, essential for therapeutic efficacy. The scaffold exhibited significant antibacterial activity against Pseudomonas aeruginosa and Staphylococcus aureus, with substantial biofilm inhibition and downregulation of bacterial genes (ndvb and icab). A wound healing assay highlighted a notable increase in MMP-2 and MMP-9 mRNA expression and the wound closure area (69.35 ± 2.21%) in HFF cells treated with Nio-Tyro@CS-AL. In vivo studies in mice confirmed the scaffold’s biocompatibility, showing no significant inflammatory response, hypertrophic scarring, or foreign body reaction. Histological evaluations revealed increased fibroblast and macrophage activity, enhanced re-epithelialization, and angiogenesis in wounds treated with Nio-Tyro@CS-AL, indicating effective tissue integration and repair. Overall, the Nio-Tyro@CS-AL scaffold presents a significant advancement in wound-healing materials, combining antibacterial properties with enhanced tissue regeneration, and holds promising potential for clinical applications in wound management.
The emergence of drug resistant pathogenic bacteria is increasingly challenging conventional antibiotics. Plant derived flavonoids are always considered as potential alternatives to antibiotics due to their antimicrobial properties. However, the molecular mechanisms by which flavonoids inhibit pathogenic microorganisms’ growth are not fully understood. In order to better understand the inhibitory mechanism of flavonoids, two flavonoids were used to incubate Klebsiella pneumoniae ATCC700603. After incubation for 4 hours, both the metabolomic and transcriptomic analysis were performed. In present study, 5,483 genes and 882 metabolites were measured. Compared to wild control, the Rutin and Luteolin induced 507 and 374 differentially expressed genes (DEGs), respectively. However, the number of differential abundant metabolites (DAMs) were the same. The correlation between DEGs and DAMs were studied. The top 10 correlated DEGs and DAMs were identified in each comparative groups. Our results showed that, compared to Luteolin, Rutin induced the accumulation of metabolites and suppressed genes’ expression. Our results provided an explanation for the disparate effects of two flavonoids and demonstrated the inhibitory mechanism of Rutin on strain growth.
The members of the genus Marrubium are of great interest because they contain biologically active compounds. With in this mind, we aimed to examine the chemical profiles and biological activities (antioxidant, enzyme inhibition and antimicrobial effects) of different extracts of Marrubium astracanicum subsp. macrodon. Extractions of the plants were carried out with the solvent n-hexane, acetone, acetone/water (70 %), and water. The antioxidant activity of these extracts was evaluated through six different assays, namely 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), cupric reducing antioxidant capacity (CUPRAC), ferric reducing antioxidant power (FRAP), metal chelating ability (MCA), and phosphomolybdenum (PBD). Additionally, the inhibitory effects of these solvents on five enzymes acetylcholinesterase (AChE), butyrylcholinesterase (BChE), tyrosinase, amylase, and glucosidase were investigated. The study detected 38 compounds in a plant, with the highest content in acetone and acetone/water extracts. The acetone/water extract demonstrated the highest antioxidant activity aligning with its superior total phenolic (51.9 mg gallic acid equivalent (GAE)/g) and flavonoid (31.0 mg rutin equivalent (RE)/g) content, highlighting a direct correlation between bioactive compound concentration and antioxidant potential across various assays. Regarding the enzyme inhibition activity, the acetone/water extract of this plant exhibited significant AChE inhibition measuring 2.5 mg galantamine equivalent (GALAE)/g and anti-glucosidase activity measuring 1.2 mmol acarbose equivalent (ACAE)/g. In antimicrobial evaluation, the acetone extract exhibited good antimicrobial activity against B. cereus at 0.2 mg/ml dose. In molecular docking analysis, delphinidin 3,5 diglucoside showed a good interaction with the active site of AChE active. Through the application of network pharmacology, an in-depth exploration was conducted to unravel the potential of compounds from M. astracanicum against Alzheimer's disease. The study specifically focused on identifying key targets within the Alzheimer's disease pathway, pinpointing crucial proteins such as Glycogen synthase kinase-3 (GSK3), Prostaglandin-endoperoxide synthase 2 (PTGS2), and Alzheimer's-associated amyloid precursor protein (APP). In summary, the plant can serve as a valuable ingredient in the production of functional products within the pharmaceutical, nutraceutical, and cosmeceutical applications.
Xanthomonas oryzae pv. oryzae (Xoo) causes a devastating bacterial leaf blight in rice. Here, the antimicrobial effects of D-limonene, L-limonene, and its oxidative derivative carveol against Xoo were investigated. We revealed that carveol treatment at ≥ 0.1 mM in liquid culture resulted in significant decrease in Xoo growth rate (> 40%) in a concentration-dependent manner, and over 1 mM, no growth was observed. The treatment with D-limonene and L-limonene also inhibited the Xoo growth but to a lesser extent compared to carveol. These results were further elaborated with the assays of motility, biofilm formation and xanthomonadin production. The carveol treatment over 1 mM caused no motilities, basal level of biofilm formation (< 10%), and significantly reduced xanthomonadin production. The biofilm formation after the treatment with two limonene isomers was decreased in a concentration-dependent manner, but the degree of the effect was not comparable to carveol. In addition, there was negligible effect on the xanthomonadin production mediated by the treatment of two limonene isomers. Field emission-scanning electron microscope (FE-SEM) unveiled that all three compounds used in this study cause severe ultrastructural morphological changes in Xoo cells, showing shrinking, shriveling, and holes on their surface. Moreover, quantitative real-time PCR revealed that carveol and D-limonene treatment significantly down-regulated the expression levels of genes involved in virulence and biofilm formation of Xoo, but not with L-limonene. Together, we suggest that limonenes and carveol will be the candidates of interest in the development of biological pesticides.
Antibiotic resistance is a global health concern. Strains of pathogenic microorganisms that have developed resistance to multiple antibiotics, such as MRSA, are extremely difficult to treat, and alternative methods for tackling pathogenic microorganisms are in demand. One potential target for new therapeutics is inhibition of quorum sensing: how microorganisms communicate and form biofilms in a density-dependent manner. Inhibiting this system via ‘quorum quenching’ (QQ) is a promising route to new pharmaceuticals and for controlling biofilm formation and growth. Quorum sensing also provides interesting possibilities in synthetic biology for producing novel products, biosensors, bioactive molecules, and so on.
This book covers the biology of quorum sensing and quenching, and potential sources of QQ enzymes and other inhibitors, as well as an overview of their mechanism and potential biotech applications. The book also covers the potential for new drug development from QQ, covering a range of related topics including protein engineering, imaging and computational studies, and integrated systems. This book is an ideal companion to researchers in chemical biology and medicinal chemistry, particularly those interested in biofilm formation, quorum sensing, novel antimicrobial development, synthetic biology and enzymology.
Antibiotic resistance is a global health concern. Strains of pathogenic microorganisms that have developed resistance to multiple antibiotics, such as MRSA, are extremely difficult to treat, and alternative methods for tackling pathogenic microorganisms are in demand. One potential target for new therapeutics is inhibition of quorum sensing: how microorganisms communicate and form biofilms in a density-dependent manner. Inhibiting this system via ‘quorum quenching’ (QQ) is a promising route to new pharmaceuticals and for controlling biofilm formation and growth. Quorum sensing also provides interesting possibilities in synthetic biology for producing novel products, biosensors, bioactive molecules, and so on.
This book covers the biology of quorum sensing and quenching, and potential sources of QQ enzymes and other inhibitors, as well as an overview of their mechanism and potential biotech applications. The book also covers the potential for new drug development from QQ, covering a range of related topics including protein engineering, imaging and computational studies, and integrated systems. This book is an ideal companion to researchers in chemical biology and medicinal chemistry, particularly those interested in biofilm formation, quorum sensing, novel antimicrobial development, synthetic biology and enzymology.
Herein, we isolated three triterpenoid saponins from the methanol extract of the fruit pulp of argan. The structures of the identified compounds were determined using comprehensive NMR spectroscopy analyses (¹H, ¹³C NMR, COSY, TOCSY, ROESY, and HSQC), combined with mass spectroscopy. Gas chromatography (GC) was utilized to determine the monosaccharide contents after the samples underwent methanolysis and their glycoside configuration was proved via their trimethylsilyl derivatives. Furthermore, the methanol extract of the fruit pulp and its n-butanol fraction were evaluated for their antioxidant properties via DPPH, ABTS, and FRAP assays, antidiabetic activity using α-amylase and α-glucosidase inhibition activities, and antibacterial properties utilizing microdilution and antibiofilm assays. Compared to the crude methanol extract, our results showed that the n-butanol fraction exhibited more potent antioxidant activity and antibacterial potential against Staphylococcus aureus, Escherichia coli, Salmonella typhi, Enterococcus faecalis, and Pseudomonas aeruginosa (MIC = 12.5–50 mg/mL); while no effect on the bacterial biofilm was observed. The methanol extract was more effective in inhibiting α-glucosidase (EC50 = 0.15 mg/mL), however, the n-butanol fraction elicited strong α-amylase inhibition (EC50 = 0.49 mg/mL). These findings suggest that the fruit pulp of argan could serve as a potential source of phytochemicals suitable for the treatment of diabetes and its related complications.
Citation: Monteiro, E.d.S.; da Silva, F.S.; Gomes, K.O.; do Prado, B.A.; dos Santos, R.D.; Gomes da Camara, C.A.; de Moraes, M.M.; Silva, I.C.R.d.; de Macêdo, V.T.; Gelfuso, G.M.; et al. Characterization and Determination of the Antibacterial Activity of Abstract: The aim of this study was to evaluate the antibacterial activity of nanoemulsions of Baccharis dracunculifolia essential oil. The volatile compounds of the essential oil were identified using gas chromatography-mass spectrometry. The properties of the nanoemulsions (droplet size, polydispersity index, pH, and electrical conductivity) were determined. The antibacterial activities of the essential oil and its nanoemulsions were evaluated using MIC, MBC, and disk diffusion. The microorganisms used were: Gram-positive bacteria (Staphylococcus aureus ATCC 25923, Bacillus cereus ATCC 14579, Streptococcus mutans ATCC 25175, and Enterococcus faecalis ATCC 29212) and Gram-negative bacteria (Pseudomonas aeruginosa ATCC 27853, Klebsiella pneumoniae ATCC BAA-1706, Salmonella enterica ATCC 14028, and Escherichia coli ATCC 25922). The major volatile compounds of the B. dracunculifolia essential oil were limonene (19.36%), (E)-nerolidol (12.75%), bicyclogermacrene (10.76%), and β-pinene (9.60%). The nanoemulsions had a mean droplet size between 13.14 and 56.84 nm. The nanoemulsions presented lower and statistically significant MIC values compared to the essential oil, indicating enhancement of the bacteriostatic action. The disk diffusion method showed that both the nanoemulsions and the essential oil presented inhibition zones only for Gram-positive bacteria, while there were no results against Gram-negative bacteria, indicating that B. dracunculifolia essential oil has a better antimicrobial effect on Gram-positive microorganisms.
Cinnamaldehyde, found in cinnamon essential oils, has been found to obstruct harmful bacteria both in laboratory experiments and in human food. Conformist antibiotics and antibacterial drugs have been effective in obstructing bacterial infections, but their excessive use has directed the development of resistant bacterial strains.
Renewed interest towards natural substances has been pushed by the widespread diffusion of antibiotic resistance. Curcumin I is the most active and effective constituent of curcuminoids extracted from Curcuma longa and, among other beneficial effects, attracted attention for its antimicrobial potential. Since the poor pharmacokinetic profile hinders its efficient utilization, in the present paper, we report encapsulation of curcumin I in poly(styrene-co-maleic acid) (SMA-CUR) providing a nanomicellar system with improved aqueous solubility and bioavailability. SMA-CUR was characterized by means of size, zeta potential, polydispersity index, atomic force microscopy (AFM), drug release studies, spectroscopic properties and stability. SMA-CUR nanoformulation displayed exciting antimicrobial properties compared to free curcumin I towards Gram-positive and Gram-negative clinical isolates.
Acidovorax avenae subsp. avenae (Aaa) is the causal agent of red stripe in sugarcane, a disease characterized by two forms: leaf stripe and top rot. Despite the importance of this disease, little is known about Aaa infection mechanisms, and studies of virulence factors (VFs) have not been reported. Previous analysis of Aaa isolates obtained from sugarcane fields in Tucumán, Argentina, suggested that pathogenicity was not related to genetic groups determined by rep‐PCR analysis. Therefore, the aims of this work were to analyse VFs produced by Aaa strains from different genetic groups and to evaluate the association among VFs, between VFs and Aaa pathogenicity and between VFs and Aaa genetic diversity. Bacterial motility (sliding, swimming and twitching), extracellular enzyme activities (proteases, amylases and endoglucanases), H 2 O 2 ‐mediated oxidative stress, cell adhesion and exopolysaccharide (EPS) production were assayed in 14 Aaa isolates from different genetic groups. Pearson's correlation analysis and principal component analysis (PCA) were performed. For each VF analysed, values were variable presenting quantitative traits among the strains. Significant correlations were observed among the VFs, though no clear trend was identified between them and the pathogenicity or genetic group. Results reinforce the idea that a single VF does not account for the infection outcome, but a more complex process occurs where the interplay among VFs must be considered. The results of this study are crucial because they provide insight into the infection mechanism of this bacterium.
c-di-GMP and its Effects on Biofilm Formation and Dispersion: a Pseudomonas Aeruginosa Review, Page 1 of 2
Abstract
Since its initial discovery as an allosteric factor regulating cellulose biosynthesis in Gluconacetobacter xylinus, the list of functional outputs regulated by c-di-GMP has grown. We have focused this article on one of these c-di-GMP-regulated processes, namely, biofilm formation in the organism Pseudomonas aeruginosa. The majority of diguanylate cyclases and phosphodiesterases encoded in the P. aeruginosa genome still remain uncharacterized; thus, there is still a great deal to be learned about the link between c-di-GMP and biofilm formation in this microbe. In particular, while a number of c-di-GMP metabolizing enzymes have been identified that participate in reversible and irreversible attachment and biofilm maturation, there is a still a significant knowledge gap regarding the c-di-GMP output systems in this organism. Even for the well-characterized Pel system, where c-di-GMP-mediated transcriptional regulation is now well documented, how binding of c-di-GMP by PelD stimulates Pel production is not understood in any detail. Similarly, c-di-GMP-mediated control of swimming, swarming and twitching also remains to be elucidated. Thus, despite terrific advances in our understanding of P. aeruginosa biofilm formation and the role of c-di-GMP in this process since the last version of this book (indeed there was no chapter on c-di-GMP!) there is still much to learn.
Chromobacterium violaceum is an opportunistic pathogen that causes infections that are difficult to treat. The goal of this research was to evaluate the effect of selected tannins (tannic acid (TA) and gallic acid (GA)) on bacterial growth, motility, antibiotic (carbenicillin, tetracycline) susceptibility, and biofilm formation. Both tannins, particularly TA, impaired bacterial growth levels and swimming motilities at sub-minimum inhibitory concentrations (sub-MICs). In combination with tannins, antibiotics showed increased MICs, suggesting that tannins interfered with antibacterial activity. Sub-MICs of tetracycline or TA alone enhanced biofilm formation of C. violaceum; however, in combination, these compounds inhibited biofilm formation. In contrast, carbenicillin at sub-MICs was effective in inhibiting C. violaceum biofilm formation; however, in combination with lower concentrations of TA or GA, biofilms were enhanced. These results provide insights into the effects of tannins on C. violaceum growth and their varying interaction with antibiotics used to target C. violaceum infections.
Sortase A (SrtA) from Gram positive pathogens is an attractive target for inhibitors due to its role in the attachment of surface proteins to the cell wall. We found that the plant natural product trans-chalcone inhibits Streptococcus mutans SrtA in vitro and also inhibited S. mutans biofilm formation. Mass spectrometry revealed that the trans-chalcone forms a Michael addition adduct with the active site cysteine. The X-ray crystal structure of the SrtA H139A mutant provided new insights into substrate recognition by the sortase family. Our study suggests that chalcone flavonoids have potential as sortase-specific oral biofilm inhibitors.
Bacterial quorum sensing (QS) is a density dependent communication system that regulates the expression of certain genes including production of virulence factors in many pathogens. Bioactive plant extract/compounds inhibiting QS regulated gene expression may be a potential candidate as antipathogenic drug. In this study anti-QS activity of peppermint (Mentha piperita) oil was first tested using the Chromobacterium violaceum CVO26 biosensor. Further, the findings of the present investigation revealed that peppermint oil (PMO) at sub-Minimum Inhibitory Concentrations (sub-MICs) strongly interfered with acyl homoserine lactone (AHL) regulated virulence factors and biofilm formation in Pseudomonas aeruginosa and Aeromonas hydrophila. The result of molecular docking analysis attributed the QS inhibitory activity exhibited by PMO to menthol. Assessment of ability of menthol to interfere with QS systems of various Gram-negative pathogens comprising diverse AHL molecules revealed that it reduced the AHL dependent production of violacein, virulence factors, and biofilm formation indicating broad-spectrum anti-QS activity. Using two Escherichia coli biosensors, MG4/pKDT17 and pEAL08-2, we also confirmed that menthol inhibited both the las and pqs QS systems. Further, findings of the in vivo studies with menthol on nematode model Caenorhabditis elegans showed significantly enhanced survival of the nematode. Our data identified menthol as a novel broad spectrum QS inhibitor.
Trigonella foenum-graecum L. (Fenugreek) is an important plant of the Leguminosae family known to have medicinal properties. However, fraction based antiquorum sensing and antibiofilm activities have not been reported from this plant. In the present study T. foenum-graecum seed extract was sequentially fractionated and sub-MICs were tested for above activities. The methanol fraction of the extract demonstrated significant inhibition of AHL regulated virulence factors: protease, LasB elastase, pyocyanin production, chitinase, EPS, and swarming motility in Pseudomonas aeruginosa PAO1 and PAF79. Further, QS dependent virulence factor in the aquatic pathogen Aeromonas hydrophila WAF38 was also reduced. Application of T. foenum-graecum seed extract to PAO1, PAF79, and WAF38 decreased the biofilm forming abilities of the pathogens by significant levels. The extract also exhibited reduced AHL levels and subsequent downregulation of lasB gene. In vivo study showed an enhanced survival of PAO1-preinfected C. elegans after treatment with extract at 1 mg/mL. Further, the major compound detected by GC-MS, caffeine, reduced the production of QS regulated virulence factors and biofilm at 200 í µí¼g/mL concentration indicating its role in the activity of the methanol extract. The results of the present study reveal the potential anti-QS and antibiofilm property of T. foenum-graceum extract and caffeine.
Sortase A (SrtA) is a cysteine transpeptidase of most Gram-positive bacteria that is responsible for the anchorage of many surface protein virulence factors to the cell wall layer. SrtA mutants are unable to display surface proteins and are defective in the establishment of infections without affecting microbial viability. In this study, we report that quercitrin (QEN), a natural compound that does not affect Staphylococcus aureus growth, can inhibit the catalytic activity of SrtA in fibrinogen (Fg) cell-clumping and immobilized fibronectin (Fn) adhesion assays. Molecular dynamics simulations and mutagenesis assays suggest that QEN binds to the binding sites of the SrtA G167A and V193A mutants. These findings indicate that QEN is a potential lead compound for the development of new anti-virulence agents against S. aureus infections.
Several virulence factors contribute to the pathogenesis of Proteus mirabilis. This study determined the inhibitory effects of allicin on urease, hemolysin, and biofilm of P. mirabilis ATCC 12453 and its antimicrobial activity against 20 clinical isolates of P. mirabilis. Allicin did not inhibit hemolysin, whereas it did inhibit relative urease activity in both prelysed (half-maximum inhibitory concentration, IC50 = 4.15μg) and intact cells (IC50 = 21μg) in a concentration-dependent manner. Allicin at sub-MIC concentrations (2-32μg mL(-1)) showed no significant effects on the growth of the bacteria (P > 0.05), but it reduced biofilm development in a concentration-dependent manner (P < 0.001). A higher concentration of allicin was needed to inhibit the established biofilms. Using the microdilution technique, the MIC90 and MBC90 values of allicin against P. mirabilis isolates were determined to be 128 μg mL(-1)and 512 μg mL(-1), respectively. The results suggest that allicin could have clinical applications in controlling P. mirabilis infections.
© FEMS 2015. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.
Background:
Inhibition and eradication of Staphylococcus aureus biofilms with conventional antibiotic is difficult, and the treatment is further complicated by the rise of antibiotic resistance among staphylococci. Consequently, there is a need for novel antimicrobials that can treat biofilm-related infections and decrease antibiotics burden. Natural compounds such as eugenol with anti-microbial properties are attractive agents that could reduce the use of conventional antibiotics. In this study we evaluated the effect of eugenol on MRSA and MSSA biofilms in vitro and bacterial colonization in vivo.
Methods and results:
Effect of eugenol on in vitro biofilm and in vivo colonization were studied using microtiter plate assay and otitis media-rat model respectively. The architecture of in vitro biofilms and in vivo colonization of bacteria was viewed with SEM. Real-time RT-PCR was used to study gene expression. Check board method was used to study the synergistic effects of eugenol and carvacrol on established biofilms. Eugenol significantly inhibited biofilms growth of MRSA and MSSA in vitro in a concentration-dependent manner. Eugenol at MIC or 2×MIC effectively eradicated the pre-established biofilms of MRSA and MSSA clinical strains. In vivo, sub-MIC of eugenol significantly decreased 88% S. aureus colonization in rat middle ear. Eugenol was observed to damage the cell-membrane and cause a leakage of the cell contents. At sub-inhibitory concentration, it decreases the expression of biofilm-and enterotoxin-related genes. Eugenol showed a synergistic effect with carvacrol on the eradication of pre-established biofilms.
Conclusion/major finding:
This study demonstrated that eugenol exhibits notable activity against MRSA and MSSA clinical strains biofilms. Eugenol inhibited biofilm formation, disrupted the cell-to-cell connections, detached the existing biofilms, and killed the bacteria in biofilms of both MRSA and MSSA with equal effectiveness. Therefore, eugenol may be used to control or eradicate S. aureus biofilm-related infections.
Type II (proteic) toxin-antitoxin (TA) operons are widely spread in bacteria and archaea. They are organized as operons in which, usually, the antitoxin gene precedes the cognate toxin gene. The antitoxin generally acts as a transcriptional self-repressor, whereas the toxin acts as a co-repressor, both proteins constituting a harmless complex. When bacteria encounter a stressful environment, TAs are triggered. The antitoxin protein is unstable and will be degraded by host proteases, releasing the free toxin to halt essential processes. The result is a cessation of cell growth or even death. Because of their ubiquity and the essential processes targeted, TAs have been proposed as good candidates for development of novel antimicrobials. We discuss here the possible druggability of TAs as antivirals and antibacterials, with focus on the potentials and the challenges that their use may find in the 'real' world. We present strategies to develop TAs as antibacterials in view of novel technologies, such as the use of very small molecules (fragments) as inhibitors of protein-protein interactions. Appropriate fragments could disrupt the T:A interfaces leading to the release of the targeted TA pair. Possible ways of delivery and formulation of Tas are also discussed.
© FEMS 2015. Published by Oxford University Press on behalf of FEMS.
Increasing bacterial resistance to available antibiotics makes the discovery of novel efficacious antibacterial agents a priority. A previous report showed that listeriolysin O (LLO) is a critical virulence factor and suggested that it is a target for developing anti-virulence drugs against Listeria monocytogenes infections. In this study, we report the discovery of LLO natural compound inhibitors with differential activity by using hemolysis assay. The mechanism of action of the inhibitors was consistent with that of fisetin, a natural flavonoid without antimicrobial activity, which we showed in our previous report via molecular simulation. Furthermore, a substantial increase in anti-hemolytic activity was observed when the single bond (C1-C2) was replaced by a double bond (C1-C2) in the inhibitor molecule. This change was based on the decomposition of the ligand-residue interaction, which indicated that the double bond (C1-C2) in the inhibitors was required for their inhibition of LLO. The current MD simulation work provides insights into the mechanism by which the compounds inhibit LLO at the atomic level and will be useful for the development of new, selective LLO inhibitors.
Pseudomonas aeruginosa is a well-known pathogenic bacterium that forms biofilms and produces virulence factors via quorum sensing (QS). Interfering with normal QS interactions between signal molecules and their cognate receptors is a developing strategy for attenuating its virulence. Here we tested the hypothesis that 6-gingerol, a pungent oil of fresh ginger, reduces biofilm formation and virulence by antagonistically binding to P. aeruginosa QS receptors. In silico studies demonstrated molecular binding occurs between 6-gingerol and the QS receptor LasR through hydrogen bonding and hydrophobic interactions. Experimentally 6-gingerol reduced biofilm formation, several virulence factors (e.g., exoprotease, rhamnolipid, and pyocyanin), and mice mortality. Further transcriptome analyses demonstrated that 6-gingerol successfully repressed QS-induced genes, specifically those related to the production of virulence factors. These results strongly support our hypothesis and offer insight into the molecular mechanism that caused QS gene repression.
Pseudomonas aeruginosa has a high propensity to develop biofilms that are resistant to exogenous deleterious agents. The aim of this study was to investigate whether carvacrol and thymol can interfere with adherence phenomena as well as acting on biofilm formation. Tests of P. aeruginosa strains showed that carvacrol and thymol interferes with the starting phases of adherence as well as with P. aeruginosa biofilms. Carvacrol and thymol (2MIC) inhibition was 97 +/- 8.5 and 89 +/- 6.3% for P. aeruginosa (ATCC 27853) and 72 +/- 4.6 and 69 +/- 6.8% for P. aeruginosa (CIP A22) adherence respectively. Carvacrol (2MIC) inhibition exceeds 90% for P. aeruginosa (ATCC 27853) and P. aeruginosa (IL5) biofilm. Thymol (2MIC) inhibition is 86 +/- 2.1, 54 +/- 5.9 and 70 +/- 4.3% for P. aeruginosa (ATCC 27853) P. aeruginosa (CIP A22), P. aeruginosa (IL5), respectively.
To demonstrate different effects of garlic extracts and their main antibiotic substance allicin, as a template for investigations on the antibacterial activity of food ingredients. Staphylococcus epidermidis ATCC 12228 and the isogenic biofilm-forming strain ATCC 35984 were used to compare the activity of allicin against planktonic bacteria and bacterial biofilms. The minimal inhibitory concentration (MIC) and the minimum biofilm inhibitory concentration (MBIC) for pure allicin were identical and reached at a concentration of 12.5 μg/mL. MBICs for standardized garlic extracts were significantly lower, with 1.56 and 0.78 μg/mL allicin for garlic water and ethanol extract, respectively. Biofilm density was impaired significantly at a concentration of 0.78 μg/mL allicin. Viability staining followed by confocal laser scanning microscopy showed, however, a 100% bactericidal effect on biofilm-embedded bacteria at a concentration of 3.13 μg/mL allicin. qRT-PCR analysis provided no convincing evidence for specific effects of allicin on biofilm-associated genes. Extracts of fresh garlic are more potent inhibitors of Staphylococcus epidermidis biofilms than pure allicin, but allicin exerts a unique bactericidal effect on biofilm-embedded bacteria. The current experimental protocol has proven to be a valid approach to characterize the antimicrobial activity of traditional food ingredients.
The rapid unchecked rise in antibiotic resistance over the last few decades has led to an increased focus on the need for alternative therapeutic strategies for the treatment and clinical management of microbial infections. In particular, small molecules that can suppress microbial virulence systems independent of any impact on growth are receiving increased attention. Quorum sensing (QS) is a cell-to-cell signalling communication system that controls the virulence behaviour of a broad spectrum of bacterial pathogens. QS systems have been proposed as an effective target, particularly as they control biofilm formation in pathogens, a key driver of antibiotic ineffectiveness. In this study, we identified coumarin, a natural plant phenolic compound, as a novel QS inhibitor, with potent anti-virulence activity in a broad spectrum of pathogens. Using a range of biosensor systems, coumarin was active against short, medium and long chain N-acyl-homoserine lactones, independent of any effect on growth. To determine if this suppression was linked to anti-virulence activity, key virulence systems were studied in the nosocomial pathogen Pseudomonas aeruginosa. Consistent with suppression of QS, coumarin inhibited biofilm, the production of phenazines and swarming motility in this organism potentially linked to reduced expression of the rhlI and pqsA quorum sensing genes. Furthermore, coumarin significantly inhibited biofilm formation and protease activity in other bacterial pathogens and inhibited bioluminescence in Aliivibrio fischeri. In light of these findings, coumarin would appear to have potential as a novel quorum sensing inhibitor with a broad spectrum of action.
Despite many advances, biomaterial-associated infections continue to be a major clinical problem. In order to minimize bacterial adhesion, material surface modifications are currently being investigated and natural products possess large potential for the design of innovative surface coatings. We report the bioguided phytochemical investigation of Pityrocarpa moniliformis and the characterization of tannins by mass spectrometry. It was demonstrated that B-type linked proanthocyanidins-coated surfaces, here termed Green coatings, reduced Gram-positive bacterial adhesion and supported mammalian cell spreading. The proposed mechanism of bacterial attachment inhibition is based on electrostatic repulsion, high hydrophilicity and the steric hindrance provided by the coating that blocks bacterium-substratum interactions. This work shows the applicability of a prototype Green-coated surface that aims to promote necessary mammalian tissue compatibility, while reducing bacterial colonization.
Piperine is a compound comprising 5-9% of black pepper (Piper nigrum), which has a variety of biological roles related to anticancer activities. Helicobacter pylori has been classified as a gastric carcinogen, because it causes gastritis and gastric cancer by injecting the virulent toxin CagA and translocating VacA. The present study investigated the inhibitory action of piperine on H. pylori growth and adhesion.
Inhibition of H. pylori growth was determined by the broth macrodilution method, and adhesion to gastric adenocarcinoma cells validated by urease assay. Motility test was performed by motility agar and the expression of adhesion gene and flagellar gene in response to the piperine treatment was assessed by RT-PCR and immunoblotting.
Administrated piperine suppressed the level of H. pylori adhesion to gastric adenocarcinoma cells in a dose dependent manner and the inhibition was statistically significant as determined by Student's t-test. In addition, piperine treatment effects on the flagellar hook gene flgE and integral membrane component of the export apparatus gene flhA expression to be suppressed and piperine diminished the H. pylori motility.
flhA, encodes an integral membrane component of the export apparatus, which is also one of the regulatory protein in the class 2 genes expression and flgE is one of them that encodes hook part of the flagella. Suppression of both genes, leads to less motility results in the organism attracted less towards to the gastric epithelial cells might be the possible reason in the adhesion inhibition. To our knowledge, this is the first report published on the inhibitory effects of piperine against the adhesion of H. pylori to gastric adenocarcinoma cells.
Streptococcus (S.) pneumoniae is a major cause of secondary bacterial pneumonia during influenza epidemics. Neuraminidase is a virulence factor of both pneumococci and influenza viruses. Bacterial neuraminidases are structurally related to viral neuraminidases and susceptible to oseltamivir, an inhibitor designed to target viral neuraminidases. This prompted us to evaluate the antipneumococcal potential of two neuraminidase inhibiting natural compounds, the diarylheptanoid katsumadain A and the isoprenylated flavone artocarpin. Chemiluminescence, fluorescence-, and hemagglutination-based enzyme assays were applied to determine the inhibitory efficiency (IC50 value) of the tested compounds towards pneumococcal neuraminidase. The mechanism of inhibition was studied via enzyme kinetics with recombinant NanA neuraminidase. Unlike oseltamivir, which competes with the natural substrate of neuraminidase, artocarpin exhibits a mixed-type inhibition with a Ki value of 9.70 μM. Remarkably, artocarpin was the only neuraminidase inhibitor for which an inhibitory effect in pneumococcal growth (MIC: 0.99–5.75 μM) and biofilm formation (MBIC: 1.15–2.97 μM) was observable. In addition, we discovered that the bactericidal effect of artocarpin can reduce the viability of pneumococci by a factor of >1000, without obvious harm to lung epithelial cells. This renders artocarpin a promising natural product for further investigations.
The long-term usage of antibiotics has resulted in the evolution of multidrug resistant bacteria, and pathogenic biofilms contribute to reduced susceptibility to antibiotics. In this study, 83 essential oils were initially screened for biofilm inhibition against Pseudomonas aeruginosa. Cinnamon bark oil and its main constituent cinnamaldehyde at 0.05% (v/v) markedly inhibited P. aeruginosa biofilm formation. Furthermore, cinnamon bark oil and eugenol decreased the production of pyocyanin and 2-heptyl-3-hydroxy-4(1H)-quinolone, the swarming motility, and the hemolytic activity of P. aeruginosa. Also, cinnamon bark oil, cinnamaldehyde, and eugenol at 0.01% (v/v) significantly decreased biofilm formation of enterohemorrhagic Escherichia coli O157:H7 (EHEC). Transcriptional analysis showed that cinnamon bark oil down-regulated curli genes and Shiga-like toxin gene stx2 in EHEC. In addition, biodegradable poly(lactic-co-glycolic acid) film incorporating biofilm inhibitors was fabricated and shown to provide efficient biofilm control on solid surfaces. This is the first report that cinnamon bark oil and its components, cinnamaldehyde and eugenol, reduce the production of pyocyanin and PQS, the swarming motility, and the hemolytic activity of P. aeruginosa, and inhibit EHEC biofilm formation.
Copyright © 2014 Elsevier B.V. All rights reserved.
BACKGROUND:
Bacteria within a biofilm are phenotypically more resistant to antibiotics, desiccation, and the host immune system, making it an important virulence factor for many microbes. Cranberry juice has long been used to prevent infections of the urinary tract, which are often related to biofilm formation. Recent studies have found that the A-type proanthocyanidins from cranberries have anti-biofilm properties against Escherichia coli.
METHODS:
Using crystal violet biofilm staining, resazurin metabolism assays, and confocal imaging, we examined the ability of A-type proanthocyanidins (PACs) to disrupt the biofilm formation of Pseudomonas aeruginosa. We used mass spectrometry to analyze the proteomic effects of PAC treatment. We also performed synergy assays and in vitro and in vivo infections to determine whether PACs, alone and in combination with gentamicin, could contribute to the killing of P. aeruginosa and the survival of cell lines and G. mellonella.
RESULTS:
Cranberry PACs reduced P. aeruginosa swarming motility. Cranberry PACs significantly disrupted the biofilm formation of P. aeruginosa. Proteomics analysis revealed significantly different proteins expressed following PAC treatment. In addition, we found that PACs potentiated the antibiotic activity of gentamicin in an in vivo model of infection using G.. mellonella.
CONCLUSIONS:
Results suggest that A-type proanthocyanidins may be a useful therapeutic against the biofilm-mediated infections caused by P. aeruginosa and should be further tested.
N-acylhomoserine lactone (AHL)-based quorum sensing (QS) is important for the regulation of proteobacterial virulence determinants. Thus, the inhibition of AHL synthases offers non-antibiotics-based therapeutic potentials against QS-mediated bacterial infections. In this work, functional AHL synthases of Pseudomonas aeruginosa LasI and RhlI were heterologously expressed in an AHL-negative Escherichia coli followed by assessments on their AHLs production using AHL biosensors and high resolution liquid chromatography-mass spectrometry (LCMS). These AHL-producing E. coli served as tools for screening AHL synthase inhibitors. Based on a campaign of screening synthetic molecules and natural products using our approach, three strongest inhibitors namely are salicylic acid, tannic acid and trans-cinnamaldehyde have been identified. LCMS analysis further confirmed tannic acid and trans-cinnemaldehyde efficiently inhibited AHL production by RhlI. We further demonstrated the application of trans-cinnemaldehyde inhibiting Rhl QS system regulated pyocyanin production in P. aeruginosa up to 42.06%. Molecular docking analysis suggested that trans-cinnemaldehyde binds to the LasI and EsaI with known structures mainly interacting with their substrate binding sites. Our data suggested a new class of QS-inhibiting agents from natural products targeting AHL synthase and provided a potential approach for facilitating the discovery of anti-QS signal synthesis as basis of novel anti-infective approach.
Biofilms are complex communities of microorganisms that attach to surfaces and are embedded in a self-produced extracellular matrix. Since these cells acquire increased tolerance against antimicrobial agents and host immune systems, biofilm-associated infectious diseases tend to become chronic. We show here that the molecular chaperone DnaK is important for biofilm formation and that chemical inhibition of DnaK cellular functions is effective in preventing biofilm development. Genetic, microbial, and microscopic analyses revealed that deletion of the dnaK gene markedly reduced the production of the extracellular functional amyloid curli, which contributes to the robustness of Escherichia coli biofilms. We tested the ability of DnaK inhibitors myricetin (Myr), telmisartan, pancuronium bromide, and zafirlukast to prevent biofilm formation of E. coli. Only Myr, a flavonol widely distributed in plants, inhibited biofilm formation in a concentration-dependent manner (IC50 = 46.2 μM); however, it did not affect growth. Transmission electron microscopy demonstrated that Myr inhibited the production of curli. Phenotypic analyses of thermo-sensitivity, cell division, intracellular level of RNA polymerase sigma factor RpoH, and vulnerability to vancomycin revealed that Myr altered the phenotype of E. coli wild type cells to make them resemble those of the isogenic dnaK deletion mutant, indicating that Myr inhibits cellular functions of DnaK. These findings provide insights into the significance of DnaK in curli-dependent biofilm formation and indicate that DnaK is an ideal target for anti-biofilm drugs.
Copyright © 2014, American Society for Microbiology. All Rights Reserved.
Ureases, enzymes that catalyze urea hydrolysis, have received considerable attention for their impact on living organisms’ health and life quality. On the one hand, the persistence of urease activity in human and animal cells can be the cause of some diseases and pathogen infections. On the other hand, food production can be negatively affected by ureases of soil microbiota that, in turn, lead to losses of nitrogenous nutrients in fields supplemented with urea as fertilizer. In this context, nature has proven to be a rich resource of natural products bearing a variety of scaffolds that decrease the ureolytic activity of ureases from different organisms. Therefore, this work compiles the state-of-the-art researches focused on the potential of plant natural products (present in extracts or as pure compounds) as urease inhibitors of clinical and/or agricultural interests. Emphasis is given to ureases of Helicobacter pylori, Canavalia ensiformis and soil microbiota although the active site of this class of hydrolases is conserved among living organisms.
In the present study, the efficacy of generally recognised as safe (GRAS) antimicrobial plant metabolites in regulating the growth of Staphylococcus aureus and S. epidermidis was investigated. Thymol, carvacrol and eugenol showed the strongest antibacterial action against these microorganisms, at a subinhibitory concentration (SIC) of ≤ 50 μg ml(-1). Genistein, hydroquinone and resveratrol showed antimicrobial effects but with a wide concentration range (SIC = 50-1,000 μg ml(-1)), while catechin, gallic acid, protocatechuic acid, p-hydroxybenzoic acid and cranberry extract were the most biologically compatible molecules (SIC ≥ 1000 μg ml(-1)). Genistein, protocatechuic acid, cranberry extract, p-hydroxybenzoic acid and resveratrol also showed anti-biofilm activity against S. aureus, but not against S. epidermidis in which, surprisingly, these metabolites stimulated biofilm formation (between 35% and 1,200%). Binary combinations of cranberry extract and resveratrol with genistein, protocatechuic or p-hydroxibenzoic acid enhanced the stimulatory effect on S. epidermidis biofilm formation and maintained or even increased S. aureus anti-biofilm activity.
Surface-attached colonies of bacteria known as biofilms play a major role in the pathogenesis of medical device infections. Biofilm colonies are notorious for their resistance to antibiotics and host defenses, which makes most device infections difficult or impossible to eradicate. Bacterial cells in a biofilm are held together by an extracellular polymeric matrix that is synthesized by the bacteria themselves. Enzymes that degrade biofilm matrix polymers have been shown to inhibit biofilm formation, detach established biofilm colonies, and render biofilm cells sensitive to killing by antimicrobial agents. This review discusses the potential use of biofilm matrix-degrading enzymes as anti-biofilm agents for the treatment and prevention of device infections. Two enzymes, deoxyribonuclease I and the glycoside hydrolase dispersin B, will be reviewed in detail. In vitro and in vivo studies demonstrating the anti-biofilm activities of these two enzymes will be summarized, and the therapeutic potential and possible drawbacks of using these enzymes as clinical agents will be discussed. (Int J Artif Organs 2009; 32: 545-54)
The calcium-independent hemolysins of Proteus mirabilis (HpmA) and Serratia marcescens (ShlA) have significant amino acid sequence similarity. These hemolysins are secreted extracellularly when expressed in E. coli. This secretion requires an amino-terminal leader sequence and the transport proteins HpmB or ShlB. We have examined truncated forms of HpmA with carboxyl-terminal deletions of various lengths on the basis of hemolytic activity and extracellular secretion. A domain necessary for stable extracellular hemolytic activity was identified between amino acids 1,034 and 1,165 of HpmA. An HpmA truncated form possessing the amino-terminal 872 amino acids of HpmA was the smallest peptide which exhibited detectable cell-bound hemolytic activity. In addition, six HpmA::PhoA protein fusions resulting from TnphoA mutagenesis of pWPM100 were examined. All of these fusion proteins were secreted to the periplasm and exhibited alkaline phosphatase activity. Despite having all of the domains necessary for secretion of HpmA, none of these protein fusion were secreted extracellularly. Finally, a comparison between these findings and the results of previously reported ShlA structure/function analyses demonstrated conservation of functional domains between these two hemolysins.
Bacteria that adhere to implanted medical devices or damaged tissue can encase themselves in a hydrated matrix of polysaccharide and protein, and form a slimy layer known as a biofilm. Antibiotic resistance of bacteria in the biofilm mode of growth contributes to the chronicity of infections such as those associated with implanted medical devices. The mechanisms of resistance in biofilms are different from the now familiar plasmids, transposons, and mutations that confer innate resistance to individual bacterial cells. In biofilms, resistance seems to depend on multicellular strategies. We summarise the features of biofilm infections, review emerging mechanisms of resistance, and discuss potential therapies.
There is a growing quest for an ideal biomaterial that shows appropriate cellular response and is not susceptible to microbial adhesion. In this study, commercial grade II titanium was submitted to RF/DC plasma surface modification at 2.2 mbar, using gas mixtures of argon, nitrogen, and oxygen at proportions 4:1:2 and 4:1:3. The surfaces were physically and chemically characterized. In order to evaluate bacterial response, the surfaces were exposed to Staphylococcus epidermidis. Oxynitrided samples, although having a higher roughness as compared with untreated samples, exhibited lower bacterial growth. This observation is probably due to the formation of different crystalline phases of nitrides and oxides caused by plasma treatment. The surface with highest contact angle and highest surface tension showed lower bacterial adhesion. These results were confirmed by scanning electron microscopy. The role of nitrogen in reducing bacterial adhesion is clear when this material is compared with untreated titanium, on which only an oxide film is present.
Chinese pharmacologist Youyou Tu developed key antimalarial drug artemisinin.
Clostridium difficile infection (CDI) is a worldwide health threat that is typically triggered by the use of broadspectrum antibiotics, which disrupt the natural gut microbiota and allow this Gram-positive anaerobic pathogen to thrive. The increased incidence and severity of disease coupled with decreased response, high recurrence rates, and emergence of multiple antibiotic-resistant strains have created an urgent need for new therapies. We describe pharmacological targeting of the cysteine protease domain (CPD) within the C. difficile major virulence factor toxin B (TcdB). Through a targeted screen with an activity-based probe for this protease domain, we identified a number of potent CPD inhibitors, including one bioactive compound, ebselen, which is currently in human clinical trials for a clinically unrelated indication. This drug showed activity against both major virulence factors, TcdA and TcdB, in biochemical and cell-based studies. Treatment in a mouse model of CDI that closely resembles the human infection confirmed a therapeutic benefit in the form of reduced disease pathology in host tissues that correlated with inhibition of the release of the toxic glucosyltransferase domain (GTD). Our results show that this non-antibiotic drug can modulate the pathology of disease and therefore could potentially be developed as a therapeutic for the treatment of CDI.
In this study, we aimed to evaluate the effect of -cyperone on S. aureus. We used a hemolysin test to examine the hemolytic activity in supernatants of S. aureus cultured with increasing concentrations of -cyperone. In addition, we evaluated the production of -hemolysin (Hla) by Western blotting. Real-time RT-PCR was performed to test the expression of hla (the gene encoding Hla) and agr (accessory gene regulator). Furthermore, we investigated the protective effect of -cyperone on Hla-induced injury of A549 lung cells by live/dead and cytotoxicity assays. We showed that in the presence of subinhibitory concentrations of -cyperone, Hla production was markedly inhibited. Moreover, -cyperone protected lung cells from Hla-induced injury. These findings indicate that -cyperone is a promising inhibitor of Hla production by S. aureus and protects lung cells from this bacterium. Thus, -cyperone may provide the basis for a new strategy to combat S. aureus pneumonia.
Serratia marcescens is an opportunistic turned obligate pathogen frequently associated with urinary tract infections (UTI) and are multidrug resistant at most instances. Quorum sensing (QS) system, a population dependent global regulatory system, controls the pathogenesis machinery of S. marcescens as it does in other pathogens. In the present study, methanol extract of a common herb and spice, Anethum graveolens (AGME) was assessed for its anti-QS potential against the clinical isolate of S. marcescens. AGME notably reduced the biofilm formation and QS dependent virulence factors production in a concentration dependent manner (64-1024 μg mL(-1)). The light and confocal microscopic images clearly evidenced the antibiofilm activity of AGME (256 μg mL(-1)) at its minimal biofilm inhibitory concentration (MBIC). Besides, in support of biochemical assays, the expression analysis of QS regulated genes fimC, bsmA and flhD which are crucial for initial adhesion and motility, confirmed their down regulation upon exposure to AGME. LC-MS analysis of AGME revealed 3-O- methyl ellagic acid (3-O-ME) as one of its active principles having nearly similar antibiofilm activity and a reduced inhibition of prodigiosin (27%) and protease (15%) compared to AGME (prodigiosin (47%) and protease (50%)). UFLC analysis revealed that 0.355 mg g(-1) of 3- O- ME was present in the AGME. AGME and the 3-O-ME significantly interfered the QS system of a QS model strain S. marcescens MG1 and its mutant S. marcescens MG44 which in turn corroborates the anti-QS mechanism of AGME.
© FEMS 2015. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.
New strategies for biofilm inhibition are becoming highly necessary because of the concerns to synthetic additives. As gallic acid (GA) is a hydrolysated natural product of tannin in Chinese gall, this research studied the effects of GA on the growth and biofilm formation of bacteria (Escherichia coli [Gram-negative] and Streptococcus mutans [Gram-positive]) under different conditions, such as nutrient levels, temperatures (25 and 37 °C) and incubation times (24 and 48 h). The minimum antimicrobial concentration of GA against the two pathogenic organisms was determined as 8 mg/mL. GA significantly affected the growth curves of both test strains at 25 and 37 °C. The nutrient level, temperature, and treatment time influenced the inhibition activity of GA on both growth and biofim formation of tested pathogens. The inhibition effect of GA on biofilm could be due to other factors in addition to the antibacterial effect. Overall, GA was most effective against cultures incubated at 37 °C for 24 h and at 25 °C for 48 h in various concentrations of nutrients and in vegetable wash waters, which indicated the potential of GA as emergent sources of biofilm control products.
© 2015 Institute of Food Technologists®
AimsThe aim of this study was to identify components of the Withania somnifera that could show anti-virulence activity against Streptococcus mutans biofilms.Methods and ResultsThe anti-acidogenic activity of fractions separated from W. somnifera was compared, and then the most active anti-acidogenic fraction was chemically characterized using gas chromatography-mass spectroscopy. The effect of the identified components on the acidogenicity, aciduricity, and extracellular polymeric substances (EPS) formation of S. mutans UA159 biofilms was evaluated. The change in accumulation and acidogenicity of S. mutans UA159 biofilms by periodic treatments (10 min per treatment) with the identified components was also investigated. Of the fractions, n-hexane fraction showed the strongest anti-acidogenic activity and was mainly composed of palmitic, linoleic, and oleic acids. Of the identified components, linoleic and oleic acids strongly affected the acid production rate, F-ATPase activity, and EPS formation of the biofilms. Periodic treatment with linoleic and oleic acids during biofilm formation also inhibited the biofilm accumulation and acid production rate of the biofilms without killing the biofilm bacteria.Conclusions
These results suggest that linoleic and oleic acids may be effective agents for restraining virulence of S. mutans biofilms.Significance and Impact of the StudyLinoleic and oleic acids may be promising agents for controlling virulence of cariogenic biofilms and subsequent dental caries formation.This article is protected by copyright. All rights reserved.
This work was focused on in vitro evaluation of anti-biofilm and antiquorum sensing effects of four selected flavonoid compounds /(+)-catechin, caffeic acid, quercetin and morin/using the strain Pseudomonas aeruginosa PAO1. At a concentration of 0.5 MIC quercetin was the only compound found to potently reduce both P. aeruginosa biofilm formation (95%) and its twitching motility. The chemical scaffold of quercetin, a common dietary polyphenol, may actually inspire development of novel and more effective medicinal agents targeting P. aeruginosa, the bacterium well known for its resistance.
Bacteria possess complex and varying cell walls with many surface exposed proteins. Sortases are responsible for the covalent attachment of specific proteins to the peptidoglycan of the cell wall of gram-positive bacteria. Sortase A of Staphylococcus aureus, which is seen as the archetypal sortase, has been shown to be essential for pathogenesis and has therefore received much attention as a potential target for novel therapeutics. Being widely present in gram-positive bacteria, it is likely that other gram-positive pathogens also require sortases for their pathogenesis. Sortases have also been shown to be of significant use in a range of industrial applications. Here we review current knowledge of the sortase family in terms of their structures, functions, and mechanisms and summarise work towards their use as antibacterial targets and microbiological tools. This article is protected by copyright. All rights reserved.
This article is protected by copyright. All rights reserved.
Five flavonostilbenes (alopecurones H, I, J, K and L) and five known ones were isolated from roots of Sophora alopecuroides, in addition to ten other phenolic compounds. A non-enzymatic interconversion of the lavandulyl-substituted flavonostilbenes was observed among alopecurones A, H, I, and K through a Wessely-Moser rearrangement reaction; this was proven by 1D and 2D NMR, HPLC-CD-PDA and HRMS analyses. Bioassay results suggested that flavonostilbenes exhibit significant antibacterial and anti-biofilm formation activities against Staphylococcus epidermidis with MIC values ranging from 3.1 to 12.5μg/mL.
Copyright © 2015. Published by Elsevier Ltd.
Considering the role of virulence factors in bacterial pathogenicity, interfering with the virulence factor production could afford a novel way for the treatment of infections caused by pathogenic bacteria. In the present study, an effect of eugenyl acetate (EA), a well-known phytochemical from Syzygium aromaticum (clove bud) was assessed for its anti-virulence potential against both Gram-negative and Gram-positive pathogens. Eugenyl acetate at 150 µg/ml, significantly inhibited virulence factor production such as pyocyanin and pyoverdin by Pseudomonas aeruginosa ATCC 27853 up to 9.4 (P < 0.01) and 3.7 fold (P < 0.01), respectively. In addition, protease activity of P. aeruginosa was significantly reduced upon treatment with EA (P < 0.05). The test compound (150 µg/ml) lowered haemolytic activity of Staphylococcus aureus ATCC 29213 up to tenfold (P < 0.01). Furthermore, a decrease in staphyloxanthin pigment production was observed when S. aureus cells were treated with increasing concentrations of EA (37.5-150 µg/ml). The test compound at 75 µg/ml exhibited quorum sensing inhibitory potential in inhibiting violacein production by Chromobacterium violaceum DMST 21761 up to 27.7 fold (P < 0.01). Thus, results of the present work reveal the potential of EA as an alternative candidate to control pathogenicity of both Gram-negative and Gram-positive organisms.
The development of new approaches for the treatment of antimicrobial-resistant infections is an urgent public health priority. The Pseudomonas aeruginosa pathogen, in particular, is a leading source of infection in hospital settings, with few available treatment options. In the context of an effort to develop antivirulence strategies to combat bacterial infection, we identified a series of highly effective small molecules that inhibit the production of pyocyanin, a redox-active virulence factor produced by P. aeruginosa. Interestingly, these new antagonists appear to suppress P. aeruginosa virulence factor production through a pathway that is independent of LasR and RhlR.
AimsTo investigate the mechanism by which morin hydrate inhibits the hemolytic activity of α-hemolysin (Hla), a channel-forming toxin that is important for the pathogenesis of disease in experimental animals, and its therapeutic effect against S. aureus pneumonia in a mouse model.Methods and ResultsThe results from the in vitro (hemolysis, western blot and cytotoxicity assays) and in vivo (mouse model of intranasal lung infection) experiments indicated that morin hydrate, a natural compound with little anti-S. aureus activity, could effectively antagonize the cytolytic activity of Hla, alleviate human lung cell injury, and protect against mortality of S. aureus pneumonia in a mouse model of infection. Molecular dynamics simulations, free energy calculations and mutagenesis assays were further employed to determine the catalytic mechanism of inhibition, which indicated that a direct binding of morin to the “Stem” domain of Hla (residues I107 and T109) and the concomitant change in conformation led to the inhibition of the self-assembly of the heptameric transmembrane pore, thus inhibiting the biological activity of Hla for cell lysis.Conclusions
Morin inhibited S. aureus virulence via inhibiting the hemolytic activity of α-hemolysin.Significance and Impact of StudyThese findings suggested that morin is a promising candidate for the development of anti-virulence therapeutic agents for the treatment of S. aureus infections.This article is protected by copyright. All rights reserved.
The chemical composition and biofilm regulation of 15 metabolites from Teucrium polium are reported. Compounds were isolated from a CH2Cl2–MeOH extract of the aerial parts of the plant and included iridoid and phenylethanol glycosides and a monoterpenoid, together with nine known compounds. The structures were elucidated based on standard spectroscopic (UV, 1H and 13C NMR), 2D NMR (1H–1H COSY, HMQC, HMBC, and NOESY), and/or LC-ESIMS/MS data analyses. Inhibition of the biofilm-forming strain Staphylococcus aureus was observed with exposure to compounds 7 and 8.
The emergence of antibiotic resistant Staphylococcus aureus presents a worldwide problem that requires non-antibiotic strategies. This study investigated the anti-biofilm and anti-hemolytic activities of four red wines and two white wines against three S. aureus strains. All red wines at 0.5-2% significantly inhibited S. aureus biofilm formation and hemolysis by S. aureus, whereas the two white wines had no effect. Furthermore, at these concentrations, red wines did not affect bacterial growth. Analyses of hemolysis and active component identification in red wines revealed that the anti-biofilm compounds and anti-hemolytic compounds largely responsible were tannic acid, trans-resveratrol, and several flavonoids. In addition, red wines attenuated S. aureus virulence in vivo in the nematode Caenorhabditis elegans, which is killed by S. aureus. These findings show that red wines and their compounds warrant further attention in antivirulence strategies against persistent S. aureus infection.
Epigallocatechin-3-gallate (EGCG), the most abundant polyphenol in green tea (Camellia sinesis) has been shown to exert antimicrobial effects on numerous bacterial pathogens. However its efficacy against Enterococcus faecalis biofilm, which is associated with persistent root canal infection is unknown. The aims of this study were to investigate the effects of EGCG against E. faecalis biofilm and virulence.
Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of EGCG on E. faecalis were determined. The efficacy of EGCG on E. faecalis biofilms was tested by exposing 7-day old E. faecalis biofilm to EGCG. Flow cytometry analysis of hydroxyphenyl fluorescein (HPF) labelled E. faecalis was used to determine if EGCG induced intracellular hydroxyl radical formation. Co-treatment of EGCG with the iron chelator 2,2-dipyridyl (DIP) was carried out to determine if hydroxyl radical generated through Fenton reaction played a role in EGCG-mediated killing of E. faecalis. Furthermore, the effects of EGCG on the expression of virulence genes in E. faecalis were evaluated by quantitative polymerase chain reaction.
EGCG exhibited a MIC and MBC of 5μg/mL and 20μg/mL respectively and effectively eradicated E. faecalis biofilms. EGCG induced the formation of hydroxyl radicals in E. faecalis. The addition of DIP protected E. faecalis against EGCG-mediated antibacterial effects. At sub-MIC, EGCG induced significant down-regulation of E. faecalis virulence genes.
EGCG is an effective antimicrobial agent against both the planktonic and biofilm forms of E. faecalis, inhibiting bacterial growth and suppressing the expression of specific genes related to virulence and biofilm formation. The antimicrobial action of EGCG on E. faecalis occurred through the generation of hydroxyl radical.
Copyright © 2014 Elsevier Ltd. All rights reserved.