Wioleta Chajęcka-Wierzchowska

University of Warmia and Mazury in Olsztyn · Department of Industrial and Food Microbiology

In this study, the tetracycline resistance of Enterococcus faecalis strains isolated from food was determined and molecular analyses of the resistance background were performed by determining the frequency of selected tetracycline resistance genes. In addition, the effect of high-pressure stress (400 and 500 MPa) on the expression of selected genes...

This study aimed to genotypic and phenotypic analyses of the enterotoxigenic potential of Staphylococcus spp. isolated from raw milk and raw milk cheeses. The presence of genes encoding staphylococcal enterotoxins (SEs), including the classical enterotoxins (sea-see), non-classical enterotoxins (seg-seu), exfoliative toxins (eta-etd) and toxic shoc...

High-pressure processing (HPP) is currently one of the leading methods of non-thermal food preservation as an alternative to traditional methods based on thermal processing. The application of HPP involves the simultaneous action of a combination of several factors—pressure values (100–600 MPa), time of operation (a few–several minutes), and temper...

High-pressure processing (HPP) is one of the non-thermal methods of food preservation considered to be safe but may cause an increase/decrease in virulence potential and antibiotic resistance. The aim of the present study was to evaluate the survival of L. monocytogenes isolates after high-pressure processing (200 and 400 MPa for 5 min) and to dete...

Staphylococcus aureus is one of the most important foodborne pathogens. S. aureus has the capability to produce a variety of toxins, including staphylococcal enterotoxins (SEs). The aim of this study was to evaluate the survival rate of S. aureus cells and analyze enterotoxins gene expression after exposure to osmotic stress and acidic/alkaline str...

One Health (OH) is one of the most essential global programs to rebalance the animal, human, and plant environments that depend on and affect each other. One element of the OH program is to draw attention to the phenomenon of antimicrobial resistance (AMR), which poses a very high risk to human and animal health. OH is not only a health-promoting p...

Due to the rich source of compounds, milk and dairy products are an excellent environment for the growth of many groups of microorganisms, including Staphylococcus aureus. The presence of pathogens in raw materials can threaten the dairy industry around the world. The objective of this study was to evaluate the prevalence and diversity of Staphyloc...

Sous-vide is a cooking technique which is considered safe for food preparation, however, the recommended temperatures and times for preparing seafood and fish may not be sufficient to ensure safety, and additionally, thermal stress may cause changes in virulence and resistance. The objective of the present investigation was to determine the reducti...

This study analyzed the effect of high-pressure processing (HPP) on the frequency of conjugal gene transfer of antibiotic resistance genes among strains obtained from starter cultures. Gene transfer ability was analyzed in vitro and in situ in the food matrix. It was found that the transfer of aminoglycoside resistance genes did not occur after hig...

Bacterial biofilm is one of the major hazards facing the food industry. Biofilm-forming ability is one of the most important virulence properties of enterococci. The genus Enterococcus includes pathogenic, spoilage, and pro-technological bacteria. The presence of enterococci in milk and dairy products is usually associated with inadequate hygiene p...

Listeria monocytogenes is an important pathogen, often associated with fish, that can adapt and survive in products and food processing plants, where it can persist for many years. It is a species characterized by diverse genotypic and phenotypic characteristics. Therefore, in this study, a total of 17 L. monocytogenes strains from fish and fish-pr...

The present study aimed to characterize and assess the diversity of CoNS strains as potential vectors for the spread of resistance to antimicrobial agents from RTE foods served in bars and restaurants. Eighty-five CoNS strains, obtained from 198 RTE food samples, were investigated. Sixty-seven CoNS isolates (78.8%) were resistant to at least one an...

This paper provides a snapshot on the pathogenic traits within CoNS isolated from ready-to-eat (RTE) food. Eighty-five strains were subjected to biofilm and slime production, as well as biofilm-associated genes (icaA, icaD, icaB, icaC, eno, bap, bhp, aap, fbe, embP and atlE), the insertion sequence elements IS256 and IS257 and hemolytic genes. The...

Cheeses produced from unpasteurized milk by traditional production methods may contain many groups of microorganisms, including Staphylococcus aureus. The aim of this study was to determine the occurrence of S. aureus in the artisanal cheese production chain from unpasteurized milk. We investigated the prevalence of S. aureus strains isolated from...

The objective of this study was to evaluate the efficiency of thyme extracts in preventing the growth of Listeria monocytogenes in frozen vegetables. In order to investigate the microbiological properties of thyme extracts, Listeria strains were isolated from frozen vegetables and identified, as well as the minimum inhibitory concentration (MIC) of...

This study analyzed the effect of high-pressure processing on the changes in resistance phenotype and expression of antibiotic resistance genes among strains from commercial starter cultures. After exposure to high pressure the expression of genes encoding resistance to aminoglycosides (aac(6′)Ie-aph(2″)Ia and aph(3′)-IIIa) decreased and the expres...

Listeria monocytogenes is a particularly foodborne pathogen associated with listeriosis, which can be disseminated in food and food processing environments. This study aimed to determine the serotypes and characteristics of virulence factors and antibiotic resistance among 40 L. monocytogenes strains isolated from food (n = 27) purchased in Olsztyn...

Food processing methods are associated with changes in environmental conditions, which may constitute a stress factor for food-related microorganisms, such as lactic acid bacteria (LAB) included in starter cultures. LAB are very valuable for the food industry, so it is important to thoroughly understand their stress response mechanisms. However, th...

Hafnia sp. and Serratia sp. belong to the Tribe Klebsielleae; although they are not considered pathogenic bacteria, there are many documented cases of diseases caused by these microorganisms. The aim of this study was to determine the antibiotic resistance profiles of strains belonging to the genus Hafnia and Serratia isolated from fish and shrimps...

This study analyzed the effect of food-related stresses on the expression of antibiotic resistance of starter and protective strains and resistance gene transfer frequency. After exposure to high-pressure processing, acidic and osmotic stress, the expression of genes encoding resistance to aminoglycosides (aac(6′)Ie-aph(2″)Ia and aph(3′)-IIIa) and/...

High-pressure processing is one of the most promising novel food preservation methods that is increasingly used in the food industry. Its biggest advantage is that it is a nonthermal method that ensures the microbiological safety of the product while maintaining other features, including nutritional value. If products made with starter cultures are...

Lactococci are lactic acid bacteria which are widely used in the form of starter cultures to obtain a wide range of food products, mainly in dairy industry in cheese and butter production. Isolates of L. lactis subsp. lactis are fast acidifiers, while isolates of L. lactis subsp. cremoris are often favored as defined starters because they tend to c...

Enterobacterales is a prevalent order, which inhabits a variety of environments including food. Due to the high similarities between pathogenic and non-pathogenic species, their identification might be difficult and laborious, and therefore there is a need for rapid and precise identification. The aim of this study was to compare the effectiveness...

Enterococci are important opportunistic pathogens with the capacity to acquire and spread antibiotic resistance. At present, linezolid-resistant enterococci (LRE) pose a great challenge. Linezolid is considered as a last resort antibiotic in the treatment of enterococcal infections, so it is important to monitor the occurrence of LRE in various env...

Ceviche is a marinated raw fish dish ready for consumption; it is a part of the cuisine of various countries on the Pacific coast and its preparation may differ among them. Although the process uses the traditional method of food preservation by lowering the pH, the exposure time is very limited, so the aim of the study was to determine the viabili...

The phenomenon of antibiotic resistance is a global problem that affects the use of antibiotics by humans and animal husbandry. One of the primary reasons for the growing phenomenon of antibiotic resistance is the over-prescription of antibiotics by doctors in human medicine and the overuse of antibiotics in industrial animal farming. Adequate educ...

This study analyzed antibiotic resistance and the occurrence of resistance genes in strains from starter and protective cultures. The largest number of obtained strains belonged to the genus Lactobacillus (n = 26; 44.9%), followed by Lactococcus (n = 17; 29.3%), Pediococcus (n = 8; 13.8%), Streptococcus (n = 4; 6.9%), Staphylococcus (n = 2; 3.4%) a...

The aim of study was to determine the occurrence of virulence factors and virulence-related genes among enterococci isolated from food of animal origin and effects of osmotic and high pressure stress on expression of virulence-related genes. The number of 78 isolates were analyzed. None of them showed a strong ability to form biofilm, 38.5% (n = 30...

High pressure processing (HPP) treatment is a promising nonthermal food preservation method that inactivates foodborne pathogens and spoilage microorganisms. Food preservation by nonthermal methods has been used for enzyme inactivation to keep the natural characteristics of foods. HPP enables to reduce the count of spoilage-causing microflora while...

Bakterie z rodzaju Enterococcus to drobnoustroje powszechnie występujące w żywności. Wzrost ilości zakażeń enterokokami sprawił, że ich antybiotykooporność i wirulencja stały się przedmiotem badań. Są one naturalnie oporne na wiele antybiotyków, mogą także nabywać oporność poprzez horyzontalny transfer genów. Opisano u nich też szereg czynników w...

The aim of this study was phenotypic and genotypic characterization of antibiotic-resistant food-borne Enterobacterales. The largest number of isolates was identified as Enterobacter cloacae (42.4%) followed by Escherichia coli (9.8%), Proteus mirabilis, Salmonella enterica, Proteus penneri, Citrobacter freundii (7.6% each), Citrobacter braakii (6....

Bakterie z rodzaju Enterococcus powszechnie występują w żywności. Wzrost ilości zakażeń enterokokami sprawił, że ich antybiotykooporność i wirulencja stały się przedmiotem badań. Są one naturalnie oporne na wiele antybiotyków, mogą także nabywać oporność poprzez horyzontalny transfer genów. Opisano u nich też szereg czynników wirulencji, m.in. hemo...

Staphylococcus aureus jest zakaźnym, oportunistycznym patogenem, który jest przyczyną wielu chorób u ludzi i zwierząt. Należy do najważniejszych patogenów przenoszonych przez żywność na świecie. Celem podjętych badań były określenie występowania oraz analiza molekularna szczepów S. aureus wyizolowanych z mleka surowego pobranego od krów z gospodars...

Listeriosis is one of the most notable foodborne diseases and is characterized by high rates of mortality. L. monocytogenes is the main cause of human listeriosis outbreaks, however, there are isolated cases of disease caused by other species of the genus Listeria. The aim of this study was to evaluate strains of L. monocytogenes (n = 7), L. innocu...

This study analyzed phenotypic and molecular resistance to tetracyclines, macrolides, glycopeptides, aminoglycosides in Enterococcus strains isolated from plant-derived food. The study involved examining 270 food samples and 72 obtained Enterococcus sp. strains were isolated and identified as E. faecium, E. faecalis and E. casseliflavus. Most of th...

Liczne doniesienia naukowe i epidemiologiczne wskazują na poważny problem dotyczący obecności Staphylococcus sp. w surowym mleku oraz w jego przetworach. Enterotoksyny gronkowcowe SEs (ang. Staphylococcal enterotoxins) charakteryzują się wysoką termostabilnością, dlatego też pozostają w produktach mlecznych nawet po zastosowaniu cieplnych metod ich...

Although coagulase-positive staphylococci are considered to be the main factor responsible for food poisoning, an increasing role for the coagulase-negative staphylococci in the production of enterotoxins has been observed in recent years. This study was conducted to assess the occurrence of genes responsible for the production of staphylococcal en...

The capacity for biofilm formation is one of the crucial factors of staphylococcal virulence. The occurrence of biofilm-forming staphylococci in raw milk may result in disturbances in technological processes in dairy factories as well as the contamination of finished food products. Therefore, this study aimed to determine the prevalence and charact...

Starter cultures are selected microbial strains intentionally added to food to obtain a product with desired organoleptic characteristics. The most important group of microorganisms used in starter cultures are bacteria, mostly lactic acid bacteria (LAB). For many years the safety criteria for the use of starter cultures in food production were bas...

The enterococci are ubiquitous bacteria able to colonize the human and animal gastrointestinal tracts and fresh and fermented food products. Their highly plastic genome allows Enterococcus spp. to gain resistance to multiple antibiotics, making infections with these organisms difficult to treat. Food-borne enterococci could be carriers of antibioti...

Shiga toxin‐producing Escherichia coli is a common foodborne pathogen which transmission includes dairy products. In the search for novel biocontrol methods, bacteriophages have become important candidates for the eradication of foodborne pathogens. The aim of this study was to evaluate the bacteriophage‐mediated reduction of E. coli O157:H7 in raw...

Wzrost świadomości społeczeństw na temat roli prawidłowego żywienia sprawia, że ludzie coraz chętniej sięgają po żywność minimalnie przetworzoną, w tym świeże warzywa i owoce. Żywność taka spożywana jest w stanie surowym, zatem wszystkie mikroorganizmy ją zasiedlające trafiają do przewodu pokarmowego konsumenta. Narastający problem związany z antyb...

Gronkowce koagulazo – ujemne (CoNS) przez wiele lat uznawane były za mikroorganizmy niepatogenne, dlatego temat ich antybiotykooporności nie był często podejmowany przez badaczy. Ostatnio wzrósł jednak ich udział w wywoływaniu infekcji ludzi i zwierząt, wykazano ponadto, że mogą stanowić rezerwuar genów oporności. Drobnoustroje te powszechnie wystę...

In Poland artisanal cheese production is an important local economic activity. Artisanal cheese is usually produced using raw cow's milk, animal rennet and salt, without the addition of starter cultures. Coagulase negative staphylococci (CoNS) are often present in artisanal cheeses. Pathogenic potential of some CoNS species, especially S. epidermid...

Antybiotykooporność stała się jednym z głównych problemów dotyczących bezpieczeństwa zdrowia publicznego. Przez długi czas zjawisko oporności bakterii na antybiotyki wiązano jedynie z presją selekcyjną w środowisku szpitalnym. Dopiero wzrastająca wiedza na temat genetycznych podstaw oporności oraz mechanizmów, jakie towarzyszą jej przekazywaniu, uk...

Gronkowce koagulazo - ujemne przez wiele lat uznawane były za mikroorganizmy niepatogenne, dlatego temat ich antybiotykooporności nie był często podejmowany przez badaczy. Ostatnio wzrósł jednak ich udział w wywoływaniu infekcji ludzi i zwierząt, wykazano ponadto, że mogą stanowić one rezerwuar genów oporności. Drobnoustroje te powszechnie występu...

Coagulase-negative staphylococci (CNS) are considered to be the cause of both nosocomial and community acquired infections worldwide. Biofilm formation by CoNS has been identified as an important factor of pathogenesis. The biofilm consists of layers of cell clusters embedded in a matrix of extracellular polysaccharide, called polysaccharide intrac...

BACKGROUND The aim of this study was to evaluate the possibility of the horizontal transfer of genes encoding resistance to aminoglycosides (aac(6′)‐Ie‐aph(2″)‐Ia, aph(2″)‐Ib, aph(2″)‐Ic, aph(2″)‐Id, ant(4′)‐Ia and ant(6′)‐Ia), tetracyclines (tetM, tetL, tetK, tetO and tetW), and macrolides (ermA, ermB, ermC, msrC, mefAB) in Enterococcus strains is...

Food producers are legally responsible for the safety of their products, including also microbiological safety. Producers are also required to define and validate shelf life, which is an integral part of the food safety management system. Challenge tests are a helpful tool in risk analysis. They are based on the assessment of growth or survival abi...

Listeria monocytogenes is a Gram-positive intracellular bacterium, which causes foodborne listeriosis. This organism can be introduced through many routes to food-processing environments and may become established on food-processing equipment. Examination of 130 meat samples was conducted and the Listeria monocytogenes prevalence was determined by...

The emergence of antibiotic-resistant strains of S. aureus such as methicillin-resistant S. aureus (MRSA) is a worldwide problem. Ready-to-eat (RTE) food which does not need thermal processing before consumption could be a vehicle for the spread of antibiotic-resistant microorganisms. The present study evaluated the molecular genetic characteristic...

The genus Staphylococcus includes spherical or slightly oval cocci with a diameter of around 0.5-1.5 μm. Genus Staphylococcus is a broad group of microorganisms, among which 47 species and 24 subspecies have been described. The basic division of these bacteria distinguishes two groups: coagulase-positive staphylococci (CPS) and coagulase-negative s...

Both the European Food Safety Authority (EFSA) and the Centers for Disease Control and Prevention (CDC) have identified Salmonella sp. as the main culprit of food poisoning around the world. Although standard methods of detecting Salmonella spp. in food by culturing are in common use and are well-developed, they consist of several stages and the ne...

The objective of the study was to answer the question of whether the ready-to-eat meat products can pose indirect hazard for consumer health serving as reservoir of Enterococcus strains harboring tetracyclines, aminoglycosides, and macrolides resistance genes. A total of 390 samples of ready-to-eat meat products were investigated. Enterococcus stra...

Enterococci have emerged as important nosocomial pathogens and have been found to possess many virulence factors, some of which are considered very important in the pathogenesis of diseases caused by them. While clinical Enterococcus strains have been extensively described in the literature, the knowledge of the virulence factors and the genetic st...

Examination of 330 food samples (meat, white raw sausage, smoked meat and cheeses) was conducted and the Salmonella spp. and Y. enterocolitica prevalence were determined. For isolated strains of Salmonella spp., it was determined whether they were of S. Typhi, S. Typhimurium or S. Enteritidis serotypes. Isolated Y. enterocolitica strains were bioty...

A total of 60 samples from retail raw, cooked and ready-to-eat shrimps were collected and the prevalence of Enterococcus spp, their virulence factors, antibiotic resistance and biofilm-forming ability was determined. Most of the strains were isolated from ready-to-eat shrimps (16/20; 80%) followed by raw shrimps (11/20; 55%) and cooked shrimps (8/2...

Yersinia enterocolitica is an important etiological factor in food poisoning. These bacteria are highly resistant to unfavourable conditions during food processing, such as low pH, salinity or disinfectants. The feature that clearly distinguishes these rods from the other Enteriobacteriaceae is the capacity to dominate the environment under refrige...

In the annual reports of the European Food Safety Authority (EFSA), Yersinia enterocolitica (YE) is enumerated as the third most common enteric pathogen responsible for food poisonings. The objective of the paper was to determine the potential for Yersinia enterocolitica growth in blue cheese and in blue cheese with a probiotic (Lactobacillus acido...

Celem badań było określenie fenotypowej i genotypowej oporności na antybiotyki szczepów z rodzaju Enterococcus spp. izolowanych z żywności (n=60) przeznaczonej do bezpośredniego spożycia, zakupionej w barach, restauracjach i fast foodach. Wyizolowano 48 szczepów, które techniką PCR zidentyfikowano jako: E. faecalis (n=21), E. faecium (n=16), E. cas...

Abstract Several methods for the rapid and specific detection of Salmonella spp. in meat have been described. This study was conducted to evaluate the capability of the VIDAS(®) UP (SPT [Salmonella Phage Technology]), an enzyme-linked fluorescent immunoassay method, and fluorescence in situ hybridization (FISH) to complement the International Organ...

Ready-to-eat (RTE) food which does not need thermal processing before consumption could be a vehicle for the spread of antibiotic-resistant microorganisms. As part of general microbiological safety checks, staphylococci are routinely enumerated in these kinds of foods.However, the presence of antibiotic resistant staphylococci in RTE food is not ro...

Salmonella sp. is one of the main causes of food poisoning. Since the standard method for detecting that pathogen in food is time-consuming, it is necessary to perfect alternative methods. In the research study, a fluorescent in situ hybridization method (FISH) was utilized with the use of a Sal3 probe to detect Salmonella sp. in chicken meat (inoc...

The studies included the determination of usefulness of the VIDAS Salmonella Xpress (SLMX) tests for Salmonella detection in poultry and its comparison with a standard cultural method International Standards Organization-6579. The material for investigation was chicken, turkey, duck and goose meat bought in retail. The study was performed on 180 me...

Yersinia enterocolitica is listed in the annual reports of the European Food Safety Authority (EFSA) as the third-most-common enteropathogen. The highly pathogenic Y. enterocolitica bioserotype 1B/O8 is geographically limited to Northern America although it has also emerged in Japan and Europe. Furthermore, the number of reports on the pathogenicit...

Garlic is valued more for its flavoring and used in a wide variety of foods. In food technology, fresh garlic is not used, but instead its processed forms, most often dried and lyophilized, are utilized. The quality and safety of the final product largely depends on their microbiological quality. This research has provided information about effect...