Fig 4 - uploaded by Lynn Hancock
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Schematic representation of a model for the organization of cell wall polymers in the cell wall of E. faecalis.
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With the goal of identifying and characterizing traits of Enterococcus faecalis that play key roles in human disease, we identified an operon specifying synthesis of a capsular carbohydrate of the type most commonly expressed by clinical isolates. This surface-exposed carbohydrate consists of glycerol phosphate, glucose, and galactose residues, and...
Context in source publication
Context 1
... and (iv) the failure of antiserum directed to this capsular material to kill strain FA2-2 in opsonophagocytosis assays (2), along with the failure of the strain used in that study to react with type 2 antiserum in the current study, the following model is proposed for the organi- zation of carbohydrates in the cell walls of E. faecalis strains (Fig. ...
Citations
... This observation is intriguing because Gram-positive bacteria naturally expose their peptidoglycan layer, which endolysins should be able to access freely. The low killing efficacy might be due to the cover of capsular polysaccharide (Hancock and Gilmore, 2002;Chan et al., 2014). Moreover, when fused with membrane-penetrating peptides, CHU-1 and CHU-2 exhibited activity against both Gram-negative and Grampositive bacteria. ...
The rise of antimicrobial resistance in ESKAPEE pathogens poses significant clinical challenges, especially in polymicrobial infections. Bacteriophage-derived endolysins offer promise in combating this crisis, but face practical hurdles. Our study focuses on engineering endolysins from a Klebsiella pneumoniae phage, fusing them with ApoE23 and COG133 peptides. We assessed the resulting chimeric proteins’ bactericidal activity against ESKAPEE pathogens in vitro. ApoE23-Kp84B (CHU-1) reduced over 3 log units of CFU for A. baumannii, E. faecalis, K. pneumoniae within 1 h, while COG133-Kp84B (CHU-2) showed significant efficacy against S. aureus. COG133-L1-Kp84B, with a GS linker insertion in CHU-2, exhibited outstanding bactericidal activity against E. cloacae and P. aeruginosa. Scanning electron microscopy revealed alterations in bacterial morphology after treatment with engineered endolysins. Notably, CHU-1 demonstrated promising anti-biofilm and anti-persister cell activity against A. baumannii and E. faecalis but had limited efficacy in a bacteremia mouse model of their coinfection. Our findings advance the field of endolysin engineering, facilitating the customization of these proteins to target specific bacterial pathogens. This approach holds promise for the development of personalized therapies tailored to combat ESKAPEE infections effectively.
... The remaining VG categories had genes present only in three E. faecalis strains (ent_C28, ent_C78 and ent_C158). These stains carried the csp operon genes, encoding for the biosynthesis of capsular polysaccharides which contribute to host immune evasion, but only two out of three strains had the seven open reading frames in the cps operon that are essential for capsule production (i.e., cpsC, cpsD, cpsE, cpsG, cpsI, cpsJ, and cpsK) [47,48]. Lastly, in the exoenzymes category, the gelE and sprE proteases, suggested to strongly contribute to pathogenesis in several infection models [49], were found in two out of the three E. faecalis strains. ...
Enterococci are commensal organisms that have probiotic effects for their hosts and can be used as adjunct cultures in fermented dairy products. The dark side of Enterococci is manifested in E. faecium and E. faecalis, which are the causative agents of nosocomial infections, and thus Enterococci have not been granted a safety status as food additives. In this context, we aimed to assess the safety and functional profile of an Enterococci collection retrieved from traditional dairy products through a high-resolution genomic characterization and comparative genomic analysis. Analysis did not reveal major differences in the main cellular processes of Enterococci. Moreover, a diverse repertoire of resistance and virulence genes was present, though known hallmark pathogenicity factors were either absent or occurred rarely. The abundance of bacteriocins and CRISPR/Cas systems suggested the ability of the isolates to suppress pathogens and evade bacteriophages, respectively. Presence–absence patterns of genes suggested that dairy-originated E. faecium are not associated with pathogenicity factors, while those of human origin are strongly linked with notorious resistance and virulence determinants. Our comparative analysis provided some notable insights regarding the genomic composition of Enterococci in the context of their origin. However, their pathogenic lifestyle is likely to be explained by the interplay of multiple genomic factors.
... Glycerol forms one of the repeating units of the extracellular polysaccharide of E. faecalis (Hancock & Gilmore 2002) with additional potential sources of glycerol coming from the recycling of lysed cells ...
Enterococcus faecalis is able to adapt to alkaline conditions and is commonly recovered from teeth in which endodontic treatment has failed. The role that E. faecalis membrane proteins play in survival strategies to extreme alkaline conditions is unclear. We grew E. faecalis V583 in a chemostat at pH 8 and pH 11 at one-tenth the organism's relative maximum growth rate. Following membrane shaving, isotope-coding protein labels were added at the peptide level to samples and then combined. The relative proportion of membrane proteins were identified using LC-ESI mass spectrometry and MaxQuant analysis. Ratios of membrane proteins were log2 transformed, with proteins deviating by more than 1 SD of the mean considered to be up- or down-regulated. Six proteins were up-regulated in pH 11 including: EF0669 (polysaccharide biosynthesis family); EF1927 (glycerol uptake facilitator) and EF0114 (glycosyl hydrolase). Five proteins were down regulated including: EF0108 (C4-dicarboxylate transporter); EF1838 (PTS system IIC component); EF0456 (PTS system IID component); EF0022 (PTS mannose-specific IID component). In extreme alkaline conditions, the membrane proteins of E.faecalis seem to be involved in a shift of carbohydrate metabolism from the PTS system to glycerol, which supports the formation of a protective capsule protecting the cell.
... Streptococcal species seem to lack orthologues of the genes that are associated with the expression of WTA (e.g., TagB, TagD, TagF) [130], while Lactococcal and Enterococcal species were reported to contain orthologues for WTA and both WTA and LTA biosynthesis, respectively, thus having a more heterogeneous expression of glycans on their surface [131][132][133][134][135]. The main constituents of the RhaCWP are rhamnose with variable combinations of Glc, GlcNAc, Gal, GalNAc, and phosphate groups, that are differently linked [136]. ...
Certain bacteria constitute a threat to humans due to their ability to escape host defenses as they easily develop drug resistance. Bacteria are classified into gram-positive and gram-negative according to the composition of the cell membrane structure. Gram-negative bacteria have an additional outer membrane (OM) that is not present in their gram-positive counterpart; the latter instead hold a thicker peptidoglycan (PG) layer. This review covers the main structural and functional properties of cell wall polysaccharides (CWPs) and PG. Drugs targeting CWPs are discussed, both noncarbohydrate-related (β-lactams, fosfomycin, and lipopeptides) and carbohydrate-related (glycopeptides and lipoglycopeptides). Bacterial resistance to these drugs continues to evolve, which calls for novel antibacterial approaches to be developed. The use of carbohydrate-based vaccines as a valid strategy to prevent bacterial infections is also addressed.
... When under selective pressure from Brockvirinae phages, Enterococcus produce mutations primarily in exopolysaccharide synthesis genes, suggesting that phage resistance may evolve by preventing phage recognition and initial binding. E. faecium and E. faecalis both contain the highly conserved Epa capsule synthesis locus, in which genetic variation has been observed consistently for E. faecalis strains (30,31,32). Mutations in the Epa locus have been observed previously during coevolution with Brockvirinae phages; these mutations impaired Enterococcus host colonization and increased antibiotic sensitivity (7,33). ...
Due to the rise in antibiotic resistance, Enterococcus infections are a major health crisis that requires the development of alternative therapies. Phage therapy offers an alternative to antibiotics and has shown promise in both in vitro and early clinical studies.
... Regarding the production of extracellular capsules by enterococci, particularly E. faecalis strains, these bacteria are endowed with this feature, and their extracellular capsules are classified into 21 unique serogroups [136]. It is significant to note that capsular antigens are sugar polymers that render strains resistant to phagocytosis and boost their persistence in a mouse model of subcutaneous infection [137]. In 2009, Thurlow et al. [138] identified an operon for capsular synthesis in a wide range of clinical strains of E. faecalis implying the potential role of these capsules in infection. ...
Citation: Ferchichi, M.; Sebei, K.; Boukerb, A.M.; Karray-Bouraoui, N.; Chevalier, S.; Feuilloley, M.G.J.; Connil, N.; Zommiti, M. Enterococcus spp.: Is It a Bad Choice for a Good Use-A Conundrum to Solve? Microorganisms 2021, 9, 2222.
... Regarding the production of extracellular capsules by enterococci, particularly E. faecalis strains, these bacteria are endowed with this feature, and their extracellular capsules are classified into 21 unique serogroups [136]. It is significant to note that capsular antigens are sugar polymers that render strains resistant to phagocytosis and boost their persistence in a mouse model of subcutaneous infection [137]. In 2009, Thurlow et al. [138] identified an operon for capsular synthesis in a wide range of clinical strains of E. faecalis implying the potential role of these capsules in infection. ...
Since antiquity, the ubiquitous lactic acid bacteria (LAB) Enterococci, which are just as predominant in both human and animal intestinal commensal flora, have been used (and still are) as probiotics in food and feed production. Their qualities encounter several hurdles, particularly in terms of the array of virulence determinants, reflecting a notorious reputation that nearly prevents their use as probiotics. Additionally, representatives of the Enterococcus spp. genus showed intrinsic resistance to several antimicrobial agents, and flexibility to acquire resistance determinants encoded on a broad array of conjugative plasmids, transposons, and bacteriophages. The presence of such pathogenic aspects among some species represents a critical barrier compromising their use as probiotics in food.
Thus, the genus neither has Generally Recognized as Safe (GRAS) status nor has it been included in the Qualified Presumption of Safety (QPS) list implying drastic legislation towards these microorganisms.
To date, the knowledge of the virulence factors and the genetic structure of foodborne enterococcal strains is rather limited. Although enterococcal infections originating from food have never been
reported, the consumption of food carrying virulence enterococci seems to be a risky path of transfer, and hence, it renders them poor choices as probiotics. Auspiciously, enterococcal virulence factors
seem to be strain specific suggesting that clinical isolates carry much more determinants that food isolates. The latter remain widely susceptible to clinically relevant antibiotics and subsequently,
have a lower potential for pathogenicity. In terms of the ideal enterococcal candidate, selected strains deemed for use in foods should not possess any virulence genes and should be susceptible to
clinically relevant antibiotics. Overall, implementation of an appropriate risk/benefit analysis, in addition to the case-by-case assessment, the establishment of a strain’s innocuity, and consideration for relevant guidelines, legislation, and regulatory aspects surrounding functional food development seem to be the crucial elements for industries, health-staff and consumers to accept enterococci, like other LAB, as important candidates for useful and beneficial applications in food industry and food biotechnology. The present review aims at shedding light on the world of hurdles and limitations that hampers the Enterococcus spp. genus and its representatives from being used or proposed for use as probiotics. The future of enterococci use as probiotics and legislation in this field are also discussed.
... Regarding the production of extracellular capsules by enterococci, particularly E. faecalis strains, these bacteria are endowed with this feature, and their extracellular capsules are classified into 21 unique serogroups [136]. It is significant to note that capsular antigens are sugar polymers that render strains resistant to phagocytosis and boost their persistence in a mouse model of subcutaneous infection [137]. In 2009, Thurlow et al. [138] identified an operon for capsular synthesis in a wide range of clinical strains of E. faecalis implying the potential role of these capsules in infection. ...
Citation: Ferchichi, M.; Sebei, K.; Boukerb, A.M.; Karray-Bouraoui, N.; Chevalier, S.; Feuilloley, M.G.J.; Connil, N.; Zommiti, M. Enterococcus spp.: Is It a Bad Choice for a Good Use-A Conundrum to Solve? Microorganisms 2021, 9, 2222.
... Regarding the production of extracellular capsules by enterococci, particularly E. faecalis strains, these bacteria are endowed with this feature, and their extracellular capsules are classified into 21 unique serogroups [136]. It is significant to note that capsular antigens are sugar polymers that render strains resistant to phagocytosis and boost their persistence in a mouse model of subcutaneous infection [137]. In 2009, Thurlow et al. [138] identified an operon for capsular synthesis in a wide range of clinical strains of E. faecalis implying the potential role of these capsules in infection. ...
Citation: Ferchichi, M.; Sebei, K.; Boukerb, A.M.; Karray-Bouraoui, N.; Chevalier, S.; Feuilloley, M.G.J.; Connil, N.; Zommiti, M. Enterococcus spp.: Is It a Bad Choice for a Good Use-A Conundrum to Solve? Microorganisms 2021, 9, 2222.
... These glycopolymers are localized at the cell surface and function as shields to mask underlying cell surface structures to reduce opsonization [98]. In E. faecalis and E. faecium, insertional inactivation of genes in the CP biosynthetic pathway yielded mutants with enhanced susceptibility to phagocytic killing by neutrophils and compromised Enterococcus' ability to persist in regional lymph nodes [99,100]. E. faecalis specifically produces 2 CP serotypes (C and D) with higher resistance to complement-mediated opsonophagocytosis than unencapsulated strains [101], contributing to innate immune evasion and increased pathogenesis [102]. ...
