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PubMed2005

Fate of Listeria monocytogenes in experimentally contaminated French sausages.

Listeria monocytogenes has been recognized as one of the most important foodborne pathogens dealt with by the food. The bacterium has been found in every part along the pork processing industry from the slaughterhouse to the cutting room and the delicatessen factories. During the fermentation and drying of sausages, L. monocytogenes tends to decrease substantially. However, despite the various hurdles in the dry sausage manufacturing process, L. monocytogenes is able to survive and is detected in the final products. The present study has evaluated growth and survival of eight different L. monocytogenes strains (originating from sausage, sausage industry environment and from clinical cases of listeriosis) in experimentally inoculated French sausages with 10(4) cfu g(-1). This study points out the fact that the decrease of L. monocytogenes contamination rate during the manufacturing process of sausages is strain dependent (p < 0.001) and mainly due to the drying and maturation step than to the fermentation itself. Whatever the strains studied, almost no decrease of the contamination rate was noted during the fermentation step. However hurdle-adapted strains (those isolated from sausages or sausage industry environment) were more difficult to cure from sausages (decrease by 1.5 log10) than non-adapted strains (decrease by 3 log10) at the end of the drying period (day 35), when sausages were ready for consumption. These sausages became safe only at the best before date. As a consequence, L. monocytogenes and more particularly those "adapted" strains might represent a very important issue for hygienists since these strains originating from sausages or production environment themselves are likely to contaminate sausages during manufacturing and remain in the final products. However, the high inoculum levels used in the study (10(4) cfu g(-1)) are not representative of the natural contamination of L. monocytogenes commonly encountered in the raw material for sausages. If such contamination happened to be inferior to 100 cfu g(-1), then the manufacturing process used in this study would be able to produce "safe" sausages according to the European regulation requiring the absence of L. monocytogenes in 25 g of food with a tolerance of below 100 cfu g(-1) at the best before date.

Animals↗

PubMed2006

Predictive model for growth of Clostridium perfringens in cooked cured pork.

Mathematical models have been developed and used for predicting growth of foodborne pathogens in various food matrices. However, these early models either used microbiological media or other model systems to develop the predictive models. Some of these models have been shown to be inaccurate for applications in meat and specific food matrices, especially under dynamic conditions, such as constantly changing temperatures that are encountered during food processing. The objective of this investigation was to develop a model for predicting growth of Clostridium perfringens from spore inocula in cured pork ham. Isothermal growth of C. perfringens at various temperatures from 10 to 48.9 degrees C were evaluated using a methodology that employed a numerical technique to solve a set of differential equations. The estimated theoretical minimum and maximum growth temperatures of C. perfringens in cooked cured pork were 13.5 and 50.6 degrees C, respectively. The kinetic and growth parameters obtained from this study can be used in evaluating growth of C. perfringens from spore populations during dynamically changing temperature conditions such as those encountered in meat processing. Further, this model can be successfully used to design microbiologically "safe" cooling regimes for cured pork hams and similar products.

Animals↗

PubMed2006

Recovery of heat-injured Listeria innocua.

Listeria innocua was subjected to thermal inactivation and the extent of heat-injured cells was quantified. Cultures were heated in liquid medium for different times, using temperatures in the range of 52.5 to 65.0 degrees C, and plated on Tryptic Soy Agar with 0.6% yeast extract (TSAYE) used as non-selective medium and on TSAYE plus 5% NaCl (TSAYE+NaCl) and Palcam agar with selective supplement (Palcam agar) as selective media. The difference observed in counts in non-selective and in selective media gave an indication of cell injury during the heat treatment. D- and z- values were calculated for all conditions considered. For each temperature, D-values obtained using non-selective recovery procedures were higher than the ones obtained using the two selective media. When comparing the selective media, it can be concluded that Palcam agar allowed recovery and growth of thermally injured cells and so it was less inhibitor than TSAYE+NaCl. Another important result was the influence of temperature on the degree of cellular injury. As temperature increases, the degree of heat-injured cells also increases, and consequently concern has to be taken with the temperature and the counting medium used in food processing studies. The results of this work clearly demonstrated that selective media used for Listeria monocytogenes enumeration/detection might not be suitable for the recovery of heat-injured cells, which can dangerously underestimate the presence of this foodborne pathogen.

Agar↗

PubMed2006

Antimicrobial effect of spices and herbs on Vibrio parahaemolyticus.

The antimicrobial effects of spices and herbs from 18 plant species were examined on a foodborne pathogen, Vibrio parahaemolyticus, with the use of combinations of temperatures and nutrient levels. Basil, clove, garlic, horseradish, marjoram, oregano, rosemary, and thyme exhibited antibacterial activities at incubation of 30 degrees C, while with the exception of horseradish, the same spices and additional 7 species exhibited the activities at 5 degrees C. The lowest MIC (minimum inhibitory concentration) was 0.125% observed in clove and marjoram at 30 degrees C in a nutrient rich medium. Lowering of incubation temperature produced little effect on the MICs except for turmeric. The decreasing of the MIC in turmeric appeared to be basically attributed to the sensitivity of the bacterium to coldness. In nutrient poor medium, the lowest was 0.001 and 0.00025% in marjoram at 30 degrees C and at 5 degrees C, respectively. The sensitivity to several spices and herbs was similar among different clinical serotypes including the emerging strain O3:K6. These results suggest that the spices and herbs can be practical for protecting seafood from the risk of contamination by V. parahaemolyticus and used in hurdle technology with low temperature.

Anti-Bacterial Agents↗

PubMed2006

A pulsed-field gel electrophoresis typing scheme for Vibrio parahaemolyticus isolates from fifteen countries.

Vibrio parahaemolyticus is an important foodborne pathogen in Taiwan and many other maritime Asian countries where seafood is frequently consumed. A total of 535 strains of V. parahaemolyticus were recovered mostly (97%) from clinical samples obtained in Taiwan or in 14 other countries. These strains were typed by pulsed-field gel electrophoresis following SfiI digestion and a typing scheme was generated. The 115 different patterns identified were grouped into 13 types with dissimilarity values less than 15, plus 16 miscellaneous patterns not grouped into any of the types. Types I, A, D and J contained the most patterns, with the numbers of patterns being 17, 13, 12, and 11, respectively. However, types I, B, D, A, H and C contained the most strains, with the numbers of strains being 204, 73, 71, 54, 29 and 25, respectively. Type I consisted exclusively of the pandemic O3:K6 strains and genetically closely related strains. This PFGE typing scheme for V. parahaemolyticus could be used for the characterization of pathogenic isolates.

Animals↗

PubMed2026

The utilization of Salmonella phage in milk and chicken: depolymerase identification and potential for anti-biofilm activity.

Bacteriophage (phage)-based biocontrol presents a promising strategy against foodborne pathogens. In this study, a novel phage, PH215, exhibited lytic activity against seven prevalent Salmonella serotypes, was isolated and characterized. PH215 demonstrated remarkable environmental stability, sustaining infectivity across a wide pH range (2-11) and at temperatures from 4 to 50 °C. The multiplicative potential of PH215 was evidenced by a low multiplicity of infection (MOI) of 10-6, a short latent period of 10 min, and a substantial burst size of approximately 50 PFU per infected cell. Genomic analysis revealed a 43,505 kb double-stranded DNA genome encoding 67 putative proteins. Notably, the product of the Peg38 gene, identified as a tail spike protein (termed PH215Depo), possessed depolymerase activity. We have shown that the cloned expression of PH215Depo exhibited enzymatic activity against various Salmonella serotypes and significantly impeded biofilm formation. Furthermore, in practical application models, PH215 application reduced Salmonella counts in milk and chicken by 2.04 to 5.37 log10 CFU/mL. Our findings highlight the potential of depolymerase-encoding phages like PH215 as effective and broad-spectrum biocontrol agents against Salmonella in the food industry.

Biofilms↗

PubMed2026

Characterization and application potential of two newly isolated phages targeting the prevalent multidrug resistant Salmonella serovars in China.

The escalating global threat of multidrug resistant (MDR) Salmonella, a foodborne pathogen with animal-derived foods serving as the primary transmission vehicle, underscores the urgent need for effective lytic phages for biocontrol. From 142 environmental and farm samples in Shandong Province, we isolated 103 phages active against MDR S. Enteritidis and S. Typhimurium, which were the most prevalent Salmonella serovars in China. Two Siphoviridae phages vB-SenS-S1 and vB-SenS-SEC2 were selected for further study. With optimal multiplicities of infection (MOIs) of 10-2 (vB-SenS-S1) and 10-5 (vB-SenS-SEC2), both phages exhibited a 20 min latent period, yielding burst sizes of 52 and 37 PFU/cell, respectively. They also demonstrated stability across a range of temperatures (50-60 °C), pH levels (5-11), and after 1 h of UV exposure. Genomic analysis identified vB-SenS-S1 (43,002 bp, 47.04% GC) and vB-SenS-SEC2 (42,948 bp, 47.65% GC) as novel double-stranded DNA phages. Functional annotation confirmed the presence of genes essential for structural assembly, host lysis, and DNA replication/metabolism, and also verified the absence of resistance, virulence, and lysogeny-associated genes. Both phages vB-SenS-S1 and vB-SenS-SEC2 exhibited synergy with colistin and tetracycline. The synergy with colistin was particularly potent, leading to complete bacterial eradication in vitro. The in vivo therapeutic efficacy was further validated in both Galleria mellonella larvae and murine models of MDR Salmonella infection. Combination therapy with vB-SenS-SEC2 and colistin not only dramatically increased survival but also achieved a significant reduction in bacterial burden across multiple visceral organs of infected mice. Moreover, vB-SenS-S1 (108 PFU/mL) completely inhibited MDR Salmonella on chicken meat at 4 °C and -20 °C when initial contamination was ≤103 CFU/mL. This study not only expands the diversity of Salmonella phages but also highlights their potential as biocontrol agents in both clinical veterinary use and food decontamination, thereby enhancing food quality and safety at both the meat production source and the terminal product.

Animals↗

PubMed2026

Potential dissemination and persistence of Clostridium perfringens along the slaughtering process in French cattle, pig or poultry slaughterhouses.

Clostridium perfringens is a major foodborne pathogen associated with meat products, yet its dissemination routes and persistence within slaughterhouses remain poorly understood. In this study, whole-genome sequencing combined with multilocus sequence typing (MLST), core genome MLST (cgMLST), and core single nucleotide polymorphism (SNP) analysis was applied to 286 C. perfringens isolates collected from cattle, pig, and poultry slaughterhouses in France. MLST analysis revealed extensive genetic diversity, with most isolates assigned to novel allelic profiles rather than previously described sequence types. Phylogenetic analyses based on cgMLST and SNP data revealed frequent recovery of closely related isolates from feces, meat, surfaces, and air, highlighting widespread dissemination of strains within slaughterhouses during processing. Notably, close genetic related isolates recovered from air and other sample types are consistent with air-associated dissemination within slaughterhouse environments. In addition, the detection of closely related strains across different sampling campaigns suggests the potential persistence of C. perfringens within slaughterhouse environments over time. Most isolates were classified as toxinotype A (97.9%), with a few belonging to toxinotypes D (1.0%) and G (1.0%), and in silico analyses revealed a broad distribution of virulence-associated genes. Antimicrobial resistance genes (ARGs) were commonly detected, particularly those conferring resistance to tetracyclines, although isolates carrying multiple ARGs remained infrequent. Overall, this study provides new insights into the genomic diversity, dissemination pathways, and persistence of C. perfringens in multi-species slaughterhouses. These findings highlight the potential role of air-associated dissemination in contamination dynamics and underscore the importance of improved hygiene control strategies to mitigate food safety risks along the meat production chain.

Antimicrobial resistance gene (ARG)↗

PubMed2026

Temporal Patterns in the Occurrence of Principal Salmonella Serotypes for Raw Meat and Poultry Products in the United States: 1998-2024.

Microbial foodborne pathogens, such as Salmonella, have the characteristic that only some subgroups of these bacteria are highly pathogenic to humans. For the Salmonella species enterica, there are more than 2,600 serotypes. These serotypes can be host-adapted so that for any animal reservoir, such as a particular food animal species, fewer than 10 serotypes make up more than fifty percent of isolates found in the reservoir. The highly concentrated nature of serotypes within a reservoir is a key to the findings of many studies and the cornerstone of some food safety programs. Nevertheless, a key limitation is that the dominant serotypes for a reservoir are likely to change over time. This is problematic because the risk of illness associated with a reservoir can increase dramatically if a more pathogenic serotype replaces one or more less pathogenic serotypes, and vice versa. In the United States, meat and poultry have been sampled continuously by the United States Department of Agriculture Food Safety and Inspection Service (USDA FSIS) for nearly 30 years. For this study, these data are used to describe how the occurrence of the most common serotypes for each sampled commodity has changed over time. Insight into how often and how rapidly the most common serotypes change is important for designing effective mitigation strategies. To aid the development of such a mitigation strategy, we developed a classification system to categorize serotypes based on the direction and magnitude of change in each serotype over time. This information is combined with a ranking system that describes the relative virulence of each serotype using genomic and epidemiological virulence patterns. We then developed a heuristic system to support risk management decisions regarding the potential risks and benefits of applying serotype-specific interventions.

Compositional data↗

PubMed2005

Detection of Shiga toxin genes stx1, stx2, and the +93 uidA mutation of E. coli O157:H7/H-using SYBR Green I in a real-time multiplex PCR.

Enterohemorrhagic Escherichia coli (EHEC) is a major foodborne pathogen capable of causing diarrhea and vomiting, but more serious complications such as hemorrhagic colitis and hemolytic-uremic syndrome (HUS) can result. A real-time PCR method to detect the presence of Shiga toxin producing E. coli (STEC) and E. coli O157:H7 was investigated using SYBR Green I (SG). Primers were designed to target the Shiga toxin genes (stx1 and stx2) and a highly conserved base substitution at +93 of the beta-glucuronidase gene (uidA) unique to E. coli O157:H7. An initial test panel of five E. coli and non-E. coli isolates was tested with individual primer sets (simplex assay) and all primer sets including stx1, stx2, and uidA (multiplex assay). All strains were correctly identified in both assays. Average melt temperatures (Tm's, degrees C) for PCR products were 85.42--stx1, 81.93--stx2, and 88.25--uidA in simplex assays and 85.20--stx1, 81.20--stx2, and 88.16--uidA when multiplexed. Each of the three gene targets in one multiplex reaction could be distinguished by melt curve data with significantly different Tm's. The assay was expanded to a panel of 138 isolates consisting of STEC, E. coli O157:H7, non-toxigenic E. coli, and non-E. coli isolates with melt peaks consistent with those stated above.

Benzothiazoles↗

PubMed2005

SlyA regulates the collagenase-mediated cytopathic phenotype in multiresistant Salmonella.

Salmonella enterica serotype Typhimurium phagetype DT104 (DT104) is a foodborne pathogen with a multiresistant phenotype conferred by a genomic-based integron structure designated as SGI1. Recently, a novel cytopathic phenotype was ascribed to several isolates of DT104 recovered from veal calves. This phenotype is dependent upon clg, a gene encoding a collagenase in Salmonella. Using a novel transposon system and an RT-PCR assay for detection of clg expression, we identified SlyA as a regulator of the collagenase-mediated phenotype. The function of SlyA, in regards to clg expression, is to repress the synthesis of Clg. Derepression ensued in the absence of SlyA or in the presence of a truncated version of SlyA with the latter being relevant for maintenance of another virulence aspect mediated by SlyA, i.e. survival within macrophages. The SlyA-mediated effect on clg expression was restricted to DT104 and other Salmonella phagetypes and serotypes possessing SGI1 thus suggesting co-regulation by an SGI1-specific component.

Amino Acid Sequence↗

PubMed2003

Identification of foodborne bacteria by infrared spectroscopy using cellular fatty acid methyl esters.

Identification of bacterial species by profiling fatty acid methyl esters (FAMEs) has commonly been carried out by using a 20-min capillary gas chromatographic procedure followed by library matching of FAME profiles using commercial MIDI databases and proprietary pattern recognition software. Fast GC (5 min) FAME procedures and mass spectrometric methodologies that require no lipid separation have also been reported. In this study, bacterial identification based on the rapid (2 min) infrared measurement of FAME mixtures was demonstrated. The microorganisms investigated included Gram positive bacteria Staphylococcus aureus, Listeria monocytogenes, Bacillus anthracis, and Bacillus cereus, and Gram negative bacteria from the family Enterobacteriacae: Yersinia enterocolitica, Salmonella typhimurium, Shigella sonnei, and Escherichia coli (four strains of E. coli), and non-Enterobacteriacae: Vibrio cholerae, Vibrio vulnificus, and Vibrio parahemolyticus. Foodborne bacterial mixtures of FAMEs were measured by using an attenuated total reflection (ATR)-Fourier transform infrared (FTIR) spectroscopic procedure and discriminated by multivariate analysis. Results showed that the Enterobacteriacae could be discriminated from the vibrios. The identification was at the level of species (for the Bacillus and Vibrio genera) or strains (for the E. coli species). A series of bacterial FAME test samples were prepared and analyzed for accuracy of identification, and all were correctly identified. Our results suggest that this infrared strategy could be used to identify foodborne pathogens.

Fatty Acids↗

PubMed2005

Detection of Listeria monocytogenes and the toxin listeriolysin O in food.

Listeria monocytogenes is an emerging bacterial foodborne pathogen responsible for listeriosis, an illness characterized by meningitis, encephalitis, and septicaemia. Less commonly, infection can result in cutaneous lesions and flu-like symptoms. In pregnant women, the pathogen can cause bacteraemia, and stillbirth or premature birth of the fetus. The mortality rate for those contracting listeriosis is approximately 20%. Currently, the United States has a zero tolerance policy regarding the presence of L. monocytogenes in food, while Canada allows only 100 cfu/g of food. As such, it is essential to be able to detect the pathogen in low numbers in food samples. One of the best ways to detect and confirm the pathogen is through the detection of one of the virulence factors, listeriolysin O (LLO) produced by the microorganism. The LLO-encoding gene (hlyA) is present only in virulent strains of the species and is required for virulence. LLO is a secreted protein toxin that can be detected easily with the use of blood agar or haemolysis assays and it is well characterized and understood. This paper focuses on some of the common methods used to detect the pathogen and the LLO toxin in food products and comments on some of the potential uses and drawbacks for the food industry.

Agar↗

PubMed2006

Effect of selective growth media on the differentiation of Salmonella enterica serovars by Fourier-Transform Mid-Infrared Spectroscopy.

Salmonella enterica serovars are prevalent foodborne pathogens responsible for high numbers of salmonellosis each year. Complex Fourier-transform infrared (FTIR) spectra offer unique biochemical fingerprints of bacteria with bands due to major cellular components. Growth media effects on discrimination of Salmonella serovars by FTIR spectroscopy were investigated and a novel sample preparation technique was developed. S. enterica strains from six serovars were grown on xylose lysine desoxycholate (XLD), Miller-Mallinson (MM), and plate count (PCA) agar as a control (37 degrees C, 24 h). Isolated colonies were suspended in 50% acetonitrile and centrifuged; the remaining pellet was placed on an AMTIR (attenuated total reflectance) crystal and dried under vacuum. Classification models (Soft Independent Modeling of Class Analogy, SIMCA), generated from derivatized infrared spectra (1300-900 cm-1 or 1200-900 cm-1), successfully discriminated among Salmonella strains with major discrimination from 1000-970 cm-1 associated to stretching modes of O-specific polysaccharide chains of lipopolysaccharides. Sample treatment with acetonitrile enhanced safe handling of the bacteria, removed interfering signals and improved the discriminating ability of SIMCA. All media were able to discriminate the S. enterica strains studied, varying in discriminating peaks and class distances in SIMCA classification. This methodology, with the production of large libraries of pathogenic bacteria, could be applied for the rapid monitoring of bacterial contamination in food with minimal sample manipulation.

Agar↗

PubMed2005

Bacteriophage P100 for control of Listeria monocytogenes in foods: genome sequence, bioinformatic analyses, oral toxicity study, and application.

Listeria monocytogenes is an opportunistic foodborne pathogen responsible for Listeriosis, a frequently fatal infection. This investigation represents a comprehensive approach to characterize and evaluate the broad host range, strictly virulent phage P100, which can infect and kill a majority of Listeria monocytogenes strains. First, the complete nucleotide sequence (131,384 basepairs) of the genome of P100 was determined, predicted to encode 174 gene products and 18 tRNAs. Bioinformatic analyses revealed that none of the putative phage proteins has any homologies to genes or proteins of Listeria or any other bacteria which are known or suspected to be toxins, pathogenicity factors, antibiotic resistance determinants, or any known allergens. Next, a repeated dose oral toxicity study in rats was conducted, which did not produce any abnormal histological changes, morbidity or mortality. Therefore, no indications for any potential risk associated with using P100 as a food additive were found. As proof of concept, and to determine the parameters for application of P100 to foods sensitive to Listeria contamination, surface-ripened red-smear soft cheese was produced. Cheeses were contaminated with low concentrations of L. monocytogenes at the beginning of the ripening period, and P100 was applied to the surface during the rind washings. Depending on the time points, frequency and dose of phage applications, we were able to obtain a significant reduction (at least 3.5 logs) or a complete eradication of Listeria viable counts, respectively. We found no evidence for phage resistance in the Listeria isolates recovered from samples. Taken together, our results indicate that P100 can provide an effective and safe measure for the control of Listeria contamination in foods and production equipment.

Animals↗

PubMed2001

Immunomagnetic separation methods for the isolation of Campylobacter jejuni from ground poultry meats.

Campylobacter jejuni is now recognized as a leading foodborne pathogen, for which poultry products constitute the main transmission route. Two alternative immunomagnetic beads (IMB) were tested for direct detection of C. jejuni ATCC 35918 in artificially inoculated ground poultry meats and culture suspension. Polyclonal anti-Campylobacter antibodies were used to coat tosylactivated Dynabeads. The same antibodies conjugated with biotin were used to label streptavidin-coated beads. After these beads were incubated with inoculated poultry slurry or culture suspension, Campylobacter-bead complexes were separated from other components with a magnet. The capture efficiency was tested by plating bead-captured cells and unbound cells in the supernatant onto Karmali agar. The effects of different coating procedures, incubation time (60, 90, 120 min), numbers of immunomagnetic beads (10(6) to 10(7)/ml) and innoculum levels (10(3) to 10(7) CFU/g or ml) were determined. Without pre-enrichment, this approach could detect 10(4) CFU/g of ground poultry meats. These methods represent a new approach to extracting, concentrating and isolating Campylobacter spp. directly from foods.

Campylobacter jejuni↗

PubMed2002

Passive immunization with convalescent serum, or oral immunization with formalin-killed organisms, does not protect mice against gastrointestinal challenge with Listeria monocytogenes.

Listeria monocytogenes is an important foodborne pathogen in both humans and animals. In addition, murine listeriosis is a widely used model for studying the molecular pathogenesis of an intracellular pathogen, and the regulation of protective cellular immunity. Little attention has been paid to protective immunity against L. monocytogenes in the gastrointestinal tract, where a secretory immune response might prevent attachment of the bacteria to the intestinal epithelium. In this study we found that neither opsonization of L. monocytogenes with immune serum, nor repeated oral administration of killed L. monocytogenes, protected mice against gastrointestinal challenge with L. monocytogenes.

Administration, Oral↗

PubMed2001

Effects of preparation method, age, and plating technique of thin agar layer media on recovery of Escherichia coli O157:H7 injured by sodium chloride.

The thin agar layer (TAL) method was experimentally tested to determine its ability to recover Escherichia coli O157:H7 injured by sodium chloride (NaCl). Cells grown in Brain Heart Infusion broth with 0%, 5%, or 7.5% (w/v) NaCl were spread and spiral plated onto Tryptic Soy agar (TSA), MacConkey Sorbitol agar (MSA), and TSA/MSA TAL combinations. Generally, TSA recovered more injured cells than TAL (p < or =0.05), and TAL recovered more cells than MSA (p < or =0.05). Preparation mode (two vs. three layers) and age (0, 1, or 7 days) of TAL had negligible effect on resuscitation of injured cells (p > 0.05). TAL, which is conventionally used to recover heat, cold, and acid-injured foodborne pathogens, may be used to recover NaCl-injured E. coli O157:H7.

Acids↗