Search

The resolution of variation within species is critical for interpreting and acting on many microbial measurements. In the key foodborne pathogens Salmonella and Escherichia coli , the primary subspecies classification scheme used is serotyping: differentiating variants within these species by surface antigen profiles. Serotype prediction from whole-genome sequencing (WGS) of isolates is now seen as comparable or preferable to traditional laboratory methods where WGS is available. However, laboratory and WGS methods depend on an isolation step that is time-consuming and incompletely represents the sample when multiple strains are present. Community sequencing approaches that skip the isolation step are, therefore, of interest for pathogen surveillance. Here, we evaluated the viability of amplicon sequencing of the full-length 16S rRNA gene for serotyping Salmonella enterica and E. coli . We developed a novel algorithm for serotype prediction, implemented as an R package (Seroplacer), which takes as input full-length 16S rRNA gene sequences and outputs serovar predictions after phylogenetic placement into a reference phylogeny. We achieved over 89% accuracy in predicting Salmonella serotypes on in silico test data and identified key pathogenic serovars of Salmonella and E. coli in isolate and environmental test samples. Although serotype prediction from 16S rRNA gene sequences is not as accurate as serotype prediction from WGS of isolates, the potential to identify dangerous serovars directly from amplicon sequencing of environmental samples is intriguing for pathogen surveillance. The capabilities developed here are also broadly relevant to other applications where intraspecies variation and direct sequencing from environmental samples could be valuable.IMPORTANCEIn order to prevent and stop outbreaks of foodborne pathogens, it is important that we can detect when pathogenic bacteria are present in a food or food-associated site and identify connections between specific pathogenic bacteria present in different samples. In this work, we develop a new computational technology that allows the important foodborne pathogens Escherichia coli and Salmonella enterica to be serotyped (a subspecies level classification) from sequencing of a single-marker gene, and the 16S rRNA gene often used to surveil bacterial communities. Our results suggest current limitations to serotyping from 16S rRNA gene sequencing alone but set the stage for further progress that we consider likely given the rapid advance in the long-read sequencing technologies and genomic databases our work leverages. If this research direction succeeds, it could enable better detection of foodborne pathogens before they reach the public and speed the resolution of foodborne pathogen outbreaks., Competing Interests: The authors declare no conflict of interest.

Enteric pathogens cycle between nutrient-rich host and nutrient-poor external environment. These pathogens compete for nutrients while cycling between host and external environment, and often experience starvation. In this context, we have studied the role of a global regulator (NtrC) of Salmonella Typhimurium. The ntr C knockout mutation caused extended lag phase (8 h) and slow growth in the minimal medium. In lag phase, the wild-type cells showed ~60-fold more expression of ntr C gene. Gene expression studies and biochemical assays showed that the extended lag phase and slow growth is due to slow metabolism, instead of nitrogen transport. Further, we observed that ntr C knockout mutation led extended lag phase and slow growth, made Δ ntr C mutant unable to compete with wild-type S. Typhimurium in both static and fluctuating nutrient condition. In addition to this, Δ ntr C knockout mutant was unable to survive long-term nitrogen starvation (150 days). The nutrient recycling assays and gene expression studies revealed that nt rC gene is essential for rapid recycling of nutrients from the dead cells. Moreover, in the absence of ntr C gene, magnesium limits the nutrient recycling efficiency of S. Typhimurium. Therefore, the ntr C gene, which is often studied with respect to nitrogen scavenging in a low nitrogen growing condition, is required even in the adequate supply of nitrogen to maintain optimal growth and fast exit from the lag phase. Hence, we conclude that, the ntr C expression is essential for competitive fitness of S. Typhimurium under the low and fluctuating nutrient condition. IMPORTANCE S. Typhimurium, both in host and external environment, faces enormous competition from other microorganisms. The competition may take place either in static or in fluctuating nutrient conditions. Thus, how S. Typhimurium as model organism we report that a global regulator NtrC, found in enteric bacteria like Escherichia coli and Salmonella, activates the set of genes and operons involved in rapid adaptation and efficient nutrient recycling/scavenging. These properties enable cells to compete with other microbes under the characteristic feast-or-famine lifestyle of S. Typhimurium as model organism we report that a global regulator NtrC, found in enteric bacteria like Escherichia coli and Salmonella, activates the set of genes and operons involved in rapid adaptation and efficient nutrient recycling/scavenging. These properties enable cells to compete with other microbes under the characteristic feast-or-famine lifestyle of S. Typhimurium. Therefore, this work helps us to understand the starvation physiology of the enteric bacterial pathogen S. Typhimurium.

Food safety is a significant public health issue in both developed and developing countries. Previous detection methods struggle to meet the current demands. We have proposed a new way to detect pathogens, allowing detection to be visualized by the naked eye. Using our newly developed assay, when target genes are present in the reaction, corresponding padlock probes form closed-loop molecules. Each reaction tube contains a pair of universal primers for identifying target genes. The ring padlock probes and corresponding universal primers start hyperbranched rolling circle amplification (HRCA) under the action of the polymerase, so as to gain branched chain amplification products, which are irreversibly entangled with magnetic particles to form aggregated magnetic particle clusters, and the detection results are visible to naked eyes. On the contrary, by using linear probes, the clustering of magnetic particles will not be produced. This method was applied to the detection of five food-borne pathogens enterohemorrhagic Escherichia coli (EHEC), enterotoxigenic Escherichia coli (ETEC), enteropathogenic Escherichia coli (EPEC), enteroinvasive Escherichia coli (EIEC) and Escherichia coli ( E. coli ), with detection limits of 1 × 10 3 , 1 × 10 4 , 1 × 10 3 , 1 × 10 4 and 1 × 10 2 CFU/mL, respectively. This method can realize multiplex automatic detection of nucleic acid and shows great development potential in the field of molecular diagnosis.

Little is known about the drivers of critically important antibacterial resistance in species with zoonotic potential present on farms (e.g., CTX-M β-lactamase-positive Escherichia coli ). We collected samples monthly between January 2017 and December 2018 on 53 dairy farms in South West England, along with data for 610 variables concerning antibacterial usage, management practices, and meteorological factors. We detected E. coli resistant to amoxicillin, ciprofloxacin, streptomycin, and tetracycline in 2,754/4,145 (66%), 263/4,145 (6%), 1,475/4,145 (36%), and 2,874/4,145 (69%), respectively, of samples from fecally contaminated on-farm and near-farm sites. E. coli positive for bla CTX-M were detected in 224/4,145 (5.4%) of samples. Multilevel, multivariable logistic regression showed antibacterial dry cow therapeutic choice (including use of cefquinome or framycetin) to be associated with higher odds of bla CTX-M positivity. Low average monthly ambient temperature was associated with lower odds of bla CTX-M E. coli positivity in samples and with lower odds of finding E. coli resistant to each of the four test antibacterials. This was in addition to the effect of temperature on total E. coli density. Furthermore, samples collected close to calves had higher odds of having E. coli resistant to each antibacterial, as well as E. coli positive for bla CTX-M Samples collected on pastureland had lower odds of having E. coli resistant to amoxicillin or tetracycline, as well as lower odds of being positive for bla CTX-M IMPORTANCE Antibacterial resistance poses a significant threat to human and animal health and global food security. Surveillance for resistance on farms is important for many reasons, including tracking impacts of interventions aimed at reducing the prevalence of resistance. In this longitudinal survey of dairy farm antibacterial resistance, we showed that local temperature-as it changes over the course of a year-was associated with the prevalence of antibacterial-resistant E. coli We also showed that prevalence of resistant E. coli was lower on pastureland and higher in environments inhabited by young animals. These findings have profound implications for routine surveillance and for surveys carried out for research. They provide important evidence that sampling at a single time point and/or single location on a farm is unlikely to be adequate to accurately determine the status of the farm regarding the presence of samples containing resistant E. coli ., (Copyright © 2021 American Society for Microbiology.)

Background: Tylosin is a commonly used in-feed antimicrobial and is approved in several countries to reduce the incidence of liver abscesses in beef cattle. Macrolides are critically important antimicrobials in human health and used to treat some foodborne bacterial diseases, such as Campylobacter jejuni and Salmonella. Feeding tylosin could select for resistant enteric bacteria in cattle, which could contaminate beef products at slaughter and potentially cause foodborne illness. We conducted a systematic review and meta-analysis to evaluate the impact of feeding tylosin to cattle on phenotypic and genotypic resistance in several potential zoonotic enteric bacteria: Enterococcus species, Escherichia coli, Salmonella enterica subspecies enterica, and Campylobacter species. This review was registered with PROSPERO (#CRD42018085949)., Results: Eleven databases were searched for primary research studies that fed tylosin at approved doses to feedlot cattle and tested bacteria of interest for phenotypic or genotypic resistance. We screened 1,626 citations and identified 13 studies that met the inclusion criteria. Enterococcus species were tested in seven studies, Escherichia coli was isolated in five studies, three studies reported on Salmonella, and two studies reported on Campylobacter species. Most studies relied on phenotypic antimicrobial susceptibility testing and seven also reported resistance gene testing. A random-effects meta-analyses of erythromycin-resistant enterococci from four studies had significant residual heterogeneity. Only two studies were available for a meta-analysis of tylosin-resistant enterococci. A semi-quantitative analysis demonstrated an increase in macrolide-resistant enterococci after long durations of tylosin administration (>100 days). Semi-quantitative analyses of other bacteria-antimicrobial combinations revealed mixed results, but many comparisons found no effect of tylosin administration. However, about half of these no-effect comparisons did not record the cumulative days of tylosin administration or the time since the last dose., Conclusions: When fed at approved dosages for typical durations, tylosin increases the proportion of macrolide-resistant enterococci in the cattle gastrointestinal tract, which could pose a zoonotic risk to human beef consumers. Feeding tylosin for short durations may mitigate the impact on macrolide-resistant enterococci and further studies are encouraged to determine the effect of minimizing or eliminating tylosin use in beef cattle. There may also be an impact on other bacteria and other antimicrobial resistances but additional details or data are needed to strengthen these comparisons. We encourage authors of antimicrobial-resistance studies to follow reporting guidelines and publish details of all comparisons to strengthen future meta-analyses., Competing Interests: Declaration of Competing Interest The authors declare that they have no competing interests., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Infections caused by extra-intestinal pathogenic Escherichia coli (ExPEC) are a serious public health problem worldwide. The most troublesome are urinary tract infections, severe neonatal meningitis, serious intraabdominal infections, and more rarely, pneumonia, intravascular-device infections, osteomyelitis, soft-tissue infections or sometimes bacteraemia. These strains are also able cause significant economic losses in animal husbandry. A thorough understanding of ExPEC ecology, reservoirs, chains and dynamics of transmission can greatly contribute to a reduction in the burden of ExPEC-associated disease. The ability of E. coli (including ExPEC) to exist and survive in various ecological niches impedes the precise recognition and indication of transmission routes most important for individual infections cases. Among many identified ExPEC reservoirs, animal companion and animals providing food seem to be important sources of infection for human; however, the real level of risk connected with potential transmission of these bacteria remains unclear. Food is indicated as one of potential ways of transmission. Despite a quite high number of reports, many of the uncertainties are expected to be reliably elucidated. This review presents most important data on the current state of knowledge concerning the potential role of food in ExPEC transmission. The possible consequences of ExPEC infections in human and animals are briefly described.

Enterobacteriaceae comprise food spoilage organisms as well as food-borne pathogens including Escherichia coli. Heat resistance in E. coli was attributed to a genomic island called the locus of heat resistance (LHR). This genomic island is also present in several other genera of Enterobacteriaceae, but its function in the enteric pathogens Salmonella enterica and Enterobacter cloacae is unknown. This study aimed to determine the frequency of the LHR in food isolates of E. coli, and its influence on heat resistance in S. enterica and Enterobacter spp. Cell counts of LHR-positive strains of E. coli, S. enterica and E. cloacae were reduced by less than 1, 1, and 4 log (cfu/mL), respectively, after exposure to 60 °C for 5 min, while cell counts of LHR-negative strains of the same species were reduced by more than 7 log (cfu/mL). Introducing an exogenous copy of the LHR into heat-sensitive enteropathogenic E. coli and S. enterica increased heat resistance to a level that was comparable to LHR-positive wild type strains. Cell counts of LHR-positive S. enterica were reduced by less than 1 log(cfu/mL) after heating to 60 °C for 5 min. Survival of LHR-positive strains was improved by increasing the NaCl concentration from 0 to 4%. Cell counts of LHR-positive strains of E. coli and S. enterica were reduced by less than 2 log (cfu/g) in ground beef patties cooked to an internal core temperature of 71 °C. This study indicates that LHR-positive Enterobacteriaceae pose a risk to food safety., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

In the food industry, successful bacterial pathogen colonization and persistence begin with their adhesion to a surface, followed by the spatial development of mature biofilm of public health concerns. Compromising bacterial settlement with natural inhibitors is a promising alternative to conventional anti-fouling treatments typically based on chemical biocides that contribute to the growing burden of antimicrobial resistance. In this study, three extracellular polymeric substance (EPS) fractions extracted from microalgae biofilms of Cylindrotheca closterium (fraction C) and Tetraselmis suecica (fraction Ta rich in insoluble scale structure and fraction Tb rich in soluble EPS) were screened for their anti-adhesive properties, against eight human food-borne pathogens belonging to Escherichia coli, Staphylococcus aureus, Salmonella enterica subsp. enterica, and Listeria monocytogenes species. The results showed that the fraction Ta was the most effective inducing statistically significant reduction for three strains of E. coli, S. aureus, and L. monocytogenes. Overall, EPSs coating on polystyrene surfaces of the different fractions increased the hydrophilic character of the support. Differences in bacterial adhesion on the different coated surfaces could be explained by several dissimilarities in the structural and physicochemical EPS compositions, according to HPLC and ATR-FTIR analysis. Interestingly, while fractions Ta and Tb were extracted from the same microalgal culture, distinct adhesion patterns were observed, highlighting the importance of the extraction process. Overall, the findings showed that EPS extracted from microalgal photosynthetic biofilms can exhibit anti-adhesive effects against food-borne pathogens and could help develop sustainable and non-toxic anti-adhesive surfaces for the food industry. Key points: •EPSs from a biofilm-based culture of C. closterium/T. suecica were characterized. •Microalgal EPS extracted from T. suecica biofilms showed bacterial anti-adhesive effects. •The anti-adhesive effect is strain-specific and affects both Gram − and Gram + bacteria. [ABSTRACT FROM AUTHOR]

ABSTRACTThe resolution of variation within species is critical for interpreting and acting on many microbial measurements. In the key foodborne pathogens Salmonella and Escherichia coli, the primary subspecies classification scheme used is serotyping: differentiating variants within these species by surface antigen profiles. Serotype prediction from whole-genome sequencing (WGS) of isolates is now seen as comparable or preferable to traditional laboratory methods where WGS is available. However, laboratory and WGS methods depend on an isolation step that is time-consuming and incompletely represents the sample when multiple strains are present. Community sequencing approaches that skip the isolation step are, therefore, of interest for pathogen surveillance. Here, we evaluated the viability of amplicon sequencing of the full-length 16S rRNA gene for serotyping Salmonella enterica and E. coli. We developed a novel algorithm for serotype prediction, implemented as an R package (Seroplacer), which takes as input full-length 16S rRNA gene sequences and outputs serovar predictions after phylogenetic placement into a reference phylogeny. We achieved over 89% accuracy in predicting Salmonella serotypes on in silico test data and identified key pathogenic serovars of Salmonella and E. coli in isolate and environmental test samples. Although serotype prediction from 16S rRNA gene sequences is not as accurate as serotype prediction from WGS of isolates, the potential to identify dangerous serovars directly from amplicon sequencing of environmental samples is intriguing for pathogen surveillance. The capabilities developed here are also broadly relevant to other applications where intraspecies variation and direct sequencing from environmental samples could be valuable.IMPORTANCEIn order to prevent and stop outbreaks of foodborne pathogens, it is important that we can detect when pathogenic bacteria are present in a food or food-associated site and identify connections between specific pathogenic bacteria present in different samples. In this work, we develop a new computational technology that allows the important foodborne pathogens Escherichia coli and Salmonella enterica to be serotyped (a subspecies level classification) from sequencing of a single-marker gene, and the 16S rRNA gene often used to surveil bacterial communities. Our results suggest current limitations to serotyping from 16S rRNA gene sequencing alone but set the stage for further progress that we consider likely given the rapid advance in the long-read sequencing technologies and genomic databases our work leverages. If this research direction succeeds, it could enable better detection of foodborne pathogens before they reach the public and speed the resolution of foodborne pathogen outbreaks.

Introduction: Due to the increasing resistance of bacteria and fungi to antimicrobials, it is necessary to search for effective alternatives to prevent and treat pathogens causing diseases in humans, animals, and plants. In this context, the mycosynthesized silver nanoparticles (AgNPs) are considered as a potential tool to combat such pathogenic microorganisms. Methods: AgNPs were synthesized from Fusarium culmorum strain JTW1 and characterized by Transmission Electron Microscopy (TEM), X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscopy, Nanoparticle Tracking Analysis (NTA), Dynamic Light Scattering (DLS) and Zeta potential measurement. The minimum inhibitory (MIC) and biocidal concentrations (MBC) were determined against 13 bacterial strains. Moreover, the combined effect of AgNPs with antibiotics (streptomycin, kanamycin, ampicillin, tetracycline) was also studied by determining the Fractional Inhibitory Concentration (FIC) index. The anti-biofilm activity was examined by crystal violet and fluorescein diacetate (FDA) assays. Furthermore, antifungal activity of AgNPs was evaluated against a panel of phytopathogenic fungi viz., Botrytis, Colletotrichum, Fusarium, Phoma, Sclerotinia, and an oomycete pathogen Phytophthora by agar well-diffusion and micro-broth dilution method to evaluate the minimal AgNPs concentrations that inhibit fungal spore germination. Results: Fungi-mediated synthesis resulted in the formation of small (15.56± 9.22 nm), spherical and stable (zeta potential of - 38.43 mV) AgNPs with good crystallinity. The results of FTIR spectroscopy indicated the presence of various functional groups, namely hydroxyl, amino, and carboxyl ones, from the biomolecules on the surface of AgNPs. The AgNPs showed antimicrobial and antibiofilm formation activities against Gram-positive and Gram-negative bacteria. The values of MIC and MBC ranged between 16-64 and 32-512 ㎍ mL-1, respectively. The enhanced effect of AgNPs in combination with antibiotics was confirmed against human pathogens. The highest synergistic effect (FIC = 0.0625) was demonstrated by the combination of AgNPs with streptomycin against two strains of Escherichia coli (ATCC 25922 and ATCC 8739), followed by Klebsiella pneumoniae and Pseudomonas aeruginosa (FIC = 0.125). Enhanced effects of AgNPs with ampicillin were also shown against Staphylococcus aureus ATCC 25923 (FIC = 0.125) and P. aeruginosa (FIC = 0.25), as well as kanamycin against S. aureus ATCC 6538 (FIC = 0.25). The crystal violet assay revealed that the lowest concentration of AgNPs (0.125 ㎍ mL-1) reduced the development of biofilms of Listeria monocytogenes and Salmonella enterica, while the maximum resistance was shown by Salmonella infantis, its biofilm was reduced after exposure to a concentration of 512㎍ mL-1. A high inhibitory effect on the activity of bacterial hydrolases was observed by the FDA assay. AgNPs at a concentration of 0.125 ㎍ mL-1 reduced the hydrolytic activity of all biofilms formed by the tested pathogens, except E. coli ATCC 25922, P. aeruginosa, and Pectobacterium carotovorum (efficient concentration was 2-fold higher, at 0.25 ㎍ mL-1), while the hydrolytic activity of E. coli ATCC 8739, Salmonella infantis and S. aureus ATCC 6538 was suppressed after treatment with AgNPs at concentrations of 0.5, 2 and 8㎍ mL-1, respectively. Moreover, AgNPs inhibited fungal growth and spore germination of Botrytis cinerea, Phoma lingam, and Sclerotinia sclerotiorum. MIC and MFC values of AgNPs against spores of these fungal strains were determined at 64, 256, and 32 ㎍ mL-1, and zones of growth inhibition were 4.93, 9.54, and 3.41 mm, respectively. Discussion: Fusarium culmorum strain JTW1 was found to be an eco-friendly biological system for an easy, efficient and inexpensive synthesis of AgNPs. In our study, the mycosynthesised AgNPs demonstrated remarkable antimicrobial (antibacterial and antifungal) and antibiofilm activities against a wide range of human and plant pathogenic bacteria and fungi singly and in combination with antibiotics. These AgNPs could be applied in medicine, agriculture, and food industry to control such pathogens that cause numerous human diseases and crop losses. However, before using them extensive animal studies are required to evaluate the toxicity, if any. [ABSTRACT FROM AUTHOR]

A culture medium contains basic elements (water, nutrients), to which are added various supplements capable of contributing to the growth of the bacteria of interest, and at the same time, inhibiting the association flora. This study aimed for testing and optimization of special supplemented culture media used for diagnosis of microbial origin foodborne pathogens. For this, performance criteria (productivity, selectivity, and specificity) of ten different culture media used for the identification and characterization of most common bacteria (i.e., Listeria monocytogenes, Salmonella spp., Escherichia coli and Staphylococcus aureus) involved in food poisoning, were investigated. For the evaluation of the performance parameters, artificial contamination was performed with Reference Materials (MR) represented by reference strains, on two levels of contamination (low and high) and blank samples. On the qualitative methods (detection of L. monocytogenes and Salmonella spp.), selectivity, specificity, accuracy, concordance and evaluation of the detection limit at 50% (LOD50) were tested; while, on the quantitative methods (enumeration of E. coli and S. aureus), repeatability, reproducibility, critical difference and measurement uncertainty were assessed. For the qualitative methods (detection of L. monocytogenes and Salmonella spp.), the evaluated parameters showed values between 82-100% and 0.429-0.564 cfu/25 g for LOD50, respectively. For the quantitative methods (enumeration of E. coli and S. aureus), the values obtained had a measurement uncertainty between 0.24-0.26 log10 cfu/g). The performance criteria (productivity, selectivity and specificity) of the culture media investigated were successfully achieved. These findings on the benefits of the addition of supplements for the culture media used to diagnose food poisoning provide further evidence of the importance of additional components with the role of enrichment, stimulation, inhibition, selection and highlighting of metabolic and enzymatic equipment. [ABSTRACT FROM AUTHOR]

Escherichia coli serotype O157:H7 is a zoonotic food- and waterborne bacterial pathogen that causes a high hospitalization rate and can cause life-threatening complications. Increasingly, E. coli O157:H7 infections appear to originate from fresh produce. Ruminants, such as cattle, are a prominent reservoir of E. coli O157:H7 in the United States. California is one of the most agriculturally productive regions in the world for fresh produce, beef, and milk. The close proximity of fresh produce and cattle presents food safety challenges on a uniquely large scale. We performed a survey of E. coli O157:H7 on 20 farms in California to observe the regional diversity and prevalence of E. coli O157:H7. Isolates were obtained from enrichment cultures of cow feces. Some farms were sampled on two dates. Genomes from isolates were sequenced to determine their relatedness and pathogenic potential. E. coli O157:H7 was isolated from approximately half of the farms. The point prevalence of E. coli O157:H7 on farms was highly variable, ranging from zero to nearly 90%. Within farms, generally one or a few lineages were found, even when the rate of isolation was high. On farms with high isolation rates, a single clonal lineage accounted for most of the isolates. Farms that were visited months after the first visit might have had the same lineages of E. coli O157:H7. Strains of E. coli O157:H7 may be persistent for months on farms.IMPORTANCE This survey of 20 cow-calf operations from different regions of California provides an in depth look at resident Escherichia coli O157:H7 populations at the molecular level. E. coli O157:H7 is found to have a highly variable prevalence, and with whole-genome sequencing, high prevalences in herds were found to be due to a single lineage shed from multiple cows. Few repeat lineages were found between farms in this area; therefore, we predict that E. coli O157:H7 has significant diversity in this area beyond what is detected in this survey. All isolates from this study were found to have pathogenic potential based on the presence of key virulence gene sequences. This represents a novel insight into pathogen diversity within a single subtype and will inform future attempts to survey regional pathogen populations.

ABSTRACT Enterohemorrhagic E. coli (EHEC) is responsible for significant human illness, death, and economic loss. The main reservoir for EHEC is cattle, but plant-based foods are common vectors for human infection. Several outbreaks have been attributed to lettuce and leafy green vegetables grown in the Salinas and Santa Maria regions of California. Bacteria causing different outbreaks are mostly not close relatives, but one group of closely-related O157:H7 has caused several of them. This unusual pattern of recurrence may have some genetic basis. Here I use whole-genome sequences to reconstruct the genetic changes that occurred in the recent ancestry of this EHEC. In a short period of time corresponding to little genetic change, there were several changes to adhesion-related sequences, mainly adhesins. These changes may have greatly altered the adhesive properties of the bacteria. Possible consequences include increased persistence of cattle infections, more bacteria shed in cattle feces, and greater virulence in humans. Similar constellations of genetic change, which are detectable by current sequencing-based surveillance, may identify other bacteria that are particular threats to human health. In addition, the Santa Maria subclade carries a nonsense mutation affecting ArsR, a repressor of genes that confer resistance to arsenic and antimony. This suggests that the persistent source of Santa Maria contamination is located in an area with arsenic-contaminated groundwater, a problem in many parts of California. This inference may aid identification of the reservoir of EHEC, which would greatly aid mitigation efforts. IMPORTANCE Food-borne bacterial infections cause substantial illness and death. Understanding how bacteria contaminate food and cause disease is important for combating the problem. Closely-related E. coli, likely originating in cattle, have repeatedly caused outbreaks spread by vegetables grown in California. Such recurrence is atypical, and might have a genetic basis. The genetic changes that occurred in the recent ancestry of these E. coli can be reconstructed from their DNA sequences. Several mutations affect genes involved in bacterial adhesion. These might affect persistence of infection in cattle, quantity of bacteria in their feces, and human disease. They also suggest a way of detecting dangerous bacteria from their genome sequences. Furthermore, a subgroup carries a mutation affecting the regulation of genes conferring arsenic resistance. This suggests that the reservoir for contamination utilizes groundwater contaminated with arsenic, a problem in parts of California. This observation may be an aid to locating the persistent reservoir of contamination.

The level of pathogens in poultry litter used for raising broiler chickens is critical to the overall health of a broiler chicken flock and food safety. Therefore, it is imperative that methods used for determining bacterial concentration in litter are accurate and reproducible across studies. In this perspective, we discuss the shortcomings associated with current methods used for bacterial quantification and detection from litter and assess the efficacy of one method for pathogen and commensal (Campylobacter , Salmonella , Escherichia coli , and Enterococcus spp.) recovery. The limit of quantitation and detection for this method differed between pathogens, and the recovery rate (∼138–208%) was higher for Salmonella , E. coli , and Enterococcus compared to Campylobacter (24%). Our results suggest that pathogen recovery from litter is highly variable and pathogen concentrations need to be reported in dry weight before comparisons can be made between studies. [ABSTRACT FROM AUTHOR]

Little is known about the drivers of critically important antibacterial resistance in species with zoonotic potential present on farms (e.g., CTX-M b-lactamase-positive Escherichia coli). We collected samples monthly between January 2017 and December 2018 on 53 dairy farms in South West England, along with data for 610 variables concerning antibacterial usage, management practices, and meteorological factors. We detected E. coli resistant to amoxicillin, ciprofloxacin, streptomycin, and tetracycline in 2,754/4,145 (66%), 263/4,145 (6%), 1,475/4,145 (36%), and 2,874/4,145 (69%), respectively, of samples from fecally contaminated on-farm and near-farm sites. E. coli positive for blaCTX-M were detected in 224/4,145 (5.4%) of samples. Multilevel, multivariable logistic regression showed antibacterial dry cow therapeutic choice (including use of cefquinome or framycetin) to be associated with higher odds of blaCTX-M positivity. Low average monthly ambient temperature was associated with lower odds of blaCTX-M E. coli positivity in samples and with lower odds of finding E. coli resistant to each of the four test antibacterials. This was in addition to the effect of temperature on total E. coli density. Furthermore, samples collected close to calves had higher odds of having E. coli resistant to each antibacterial, as well as E. coli positive for blaCTX-M. Samples collected on pastureland had lower odds of having E. coli resistant to amoxicillin or tetracycline, as well as lower odds of being positive for blaCTX-M. IMPORTANCE Antibacterial resistance poses a significant threat to human and animal health and global food security. Surveillance for resistance on farms is important for many reasons, including tracking impacts of interventions aimed at reducing the prevalence of resistance. In this longitudinal survey of dairy farm antibacterial resistance, we showed that local temperature--as it changes over the course of a year--was associated with the prevalence of antibacterial-resistant E. coli. We also showed that prevalence of resistant E. coli was lower on pastureland and higher in environments inhabited by young animals. These findings have profound implications for routine surveillance and for surveys carried out for research. They provide important evidence that sampling at a single time point and/or single location on a farm is unlikely to be adequate to accurately determine the status of the farm regarding the presence of samples containing resistant E. coli. [ABSTRACT FROM AUTHOR]

Aims: The objective of this study was to evaluate the antimicrobial effects of radio frequency (RF) heating and the combination treatment of RF heating with ultraviolet (UV) radiation against foodborne pathogens in roasted grain powder (RGP). Methods and Results: Foodborne pathogens inoculated on RGP were subjected to RF heating or RF-UV combination treatments. After 120 s of RF heating, 4•68, 3•89 and 4•54 log reductions were observed for Escherichia coli, Salmonella Typhimurium and Bacillus cereus vegetative cells respectively. The combined RF-UV treatment showed synergistic effects of over 1 log unit compared to the sum of individual treatment for E. coli and S. Typhimurium, but not for B. cereus vegetative cells because of their high UV resistance. Germinated B. cereus cells were not significantly inactivated by RF heating (<1 log CFU per gram), and increased heat resistance compared to the vegetative cells was verified with mild heat treatment. The colour of RGP was not significantly affected by the RF or RF-UV treatments. Conclusions: Applying RF heating to grain-based food products has advantages for the inactivation of E. coli and S. Typhimurium in RGP. Significance and Impact of the Study: The results of the present study could be used as a basis for determining the treatment conditions for inactivating E. coli and other foodborne pathogens such as S. Typhimurium and B. cereus in RGP. [ABSTRACT FROM AUTHOR]

Color-switch electrochemiluminescence (ECL) sensing platform based on a dual-bipolar electrode (D-BPE) is reported in this work. The D-BPE was composed of a cathode filled with buffer and two anodes filled with [Ru(bpy) 3 ]2+-TPrA and luminol-H 2 O 2 solutions, respectively. Both anodes were modified with capture DNA and served as ECL reporting platforms. After introducing ferrocene-labeled aptamer (Fc-aptamer) on both anodes, the ECL emission signal of the [Ru(bpy) 3 ]2+ was difficult to be observed (anode 1), while luminol emitted a strong and visible ECL signal (anode 2). Ferrocene (Fc) did not only prevent the oxidation of [Ru(bpy) 3 ]2+ due to its lower oxidation potential, its oxidation product Fc+ also quenched the [Ru(bpy) 3 ]2+ ECL through efficient energy transfer. For luminol, Fc+ catalyzes the accelerated formation of the excited-state of the luminol anion radical, which leads to the enhancement of the luminol ECL. In the presence of food-borne pathogens, the aptamer was assembled with them, leading to the leaving of Fc from the surface of the D-BPE anodes. The ECL intensity of [Ru(bpy) 3 ]2+ was enlarged, meanwhile, the blue emission signal of luminol became weakened. By self-calibrating the ratio of the two signals, 1–106 CFU mL−1 food-borne pathogenic bacteria can be sensitively detected with a detection limit of 1 CFU mL−1. Ingeniously, the color-switch biosensor can be used to detect S. aureus , E. coli and S. typhimurium by assembling the corresponding aptamers onto the D-BPE anodes. [ABSTRACT FROM AUTHOR]

Although lateral-flow test strip (LFTS) immunoassays are rapid and require no specialized equipment, they are less sensitive than culture and polymerase chain reaction (PCR)-based methods for detecting bacteria. This study compared the sensitivity of LFTS assays based on colloidal palladium nanoparticles (PdNPs) and colloidal gold nanoparticles (AuNPs). PdNPs demonstrated a time and concentration dependent oxidation of the horseradish peroxidase (HRP) substrate 3,3′,5,5′-tetramethylbenzidine (TMB), whereas AuNPs did not. PdNPs labeled HRP-conjugated antibody lateral flow test strip (PdNPs-HRP LFTS) assays were tested with 3,3′-diaminobenzidine (DAB), a water insoluble substrate. The sensitivity of PdNPs-HRP LFTS assays in detecting Listeria monocytogenes, Escherichia coli O157:H7 and Yersinia enterocolitica was 5–10-fold higher than that of AuNPs-based LFTS (AuNPs LFTS) assays. PdNPs-HRP LFTS assays of reduced milk inoculated with L. monocytogenes were more than 10-fold more sensitive than conventional AuNPs LFTS assays. These results suggest that the PdNPs-HRP LFTS immunoassay is a promising tool for ensuring food safety. [ABSTRACT FROM AUTHOR]

Antimicrobial use in beef cattle can increase antimicrobial resistance prevalence in their enteric bacteria, including potential pathogens such as Escherichia coli. These bacteria can contaminate animal products at slaughterhouses and cause food-borne illness, which can be difficult to treat if it is due to antimicrobial resistant bacteria. One potential intervention to reduce the dissemination of resistant bacteria from feedlot to consumer is to impose a withdrawal period after antimicrobial use, similar to the current withdrawal period designed to prevent drug residues in edible animal meat. We investigated tetracycline resistance in generic E. coli in the bovine large intestine during and after antimicrobial treatment by building a mathematical model of oral chlortetracycline pharmacokinetics-pharmacodynamics and E. coli population dynamics. We tracked three E. coli subpopulations (susceptible, intermediate, and resistant) during and after treatment with each of three United States chlortetracycline indications (liver abscess reduction, disease control, disease treatment). We compared the proportion of resistant E. coli before antimicrobial use to that at several time points after treatment and found a greater proportion of resistant enteric E. coli after the current withdrawal periods than prior to treatment. In order for the proportion of resistant E. coli in the median beef steer to return to the pre-treatment level, withdrawal periods of 15 days after liver abscess reduction dosing (70mg daily), 31 days after disease control dosing (350mg daily), and 36 days after disease treatment dosing (22 mg/kg bodyweight for 5 days) are required in this model. These antimicrobial resistance withdrawal periods would be substantially longer than the current U.S. withdrawals of 0-2 days or Canadian withdrawals of 5-10 days. One published field study found similar time periods necessary to reduce the proportion of resistant E. coli following chlortetracycline disease treatment to those suggested by this model, but additional carefully designed field studies are necessary to confirm the model results. This model is limited to biological processes within the cattle and does not include resistance selection in the feedlot environment or co-selection of chlortetracycline resistance following other antimicrobial use. [ABSTRACT FROM AUTHOR]

Chili peppers ( Capsicum spp.) may possess antibacterial properties and have potential to be used in foods as antimicrobial. The complete chili pepper extract should be evaluated to determine which compounds are responsible for the antimicrobial activity. Extraction of compounds from the pepper is completed using a solvent. The type of solvent used for extraction influences which compounds are isolated, therefore the best extraction method needs to be determined. The purpose of this study was to identify which solvent is most successful at extracting unknown antibacterial compounds from jalapeño peppers. Fresh jalapeño peppers were chopped, weighed, and blended with a solvent (sterilized hot water, 70% methanol, 95% methanol, 70% ethanol, or 95% ethanol) at a 1:1 ratio (g/g) until the mixture was homogenized, followed by shaking for 15 min. The slurry was centrifuged; supernatant was removed and used for antibacterial testing against Listeria monocytogenes, Escherichia coli O157:H7, and Salmonella enterica. The diameter of growth inhibition was measured and statistically evaluated using ANOVA to determine the extract with the greatest antimicrobial activity. Solvents were tested alone as a control. There was greater bacterial inhibition from extracts created with methanol and ethanol than hot water. Listeria monocytogenes was significantly more susceptible to the extracts than E. coli or Salmonella isolates. Each solvent extract was then analyzed using high-performance liquid chromatography (HPLC) and fractions (A-G) were collected and used for subsequent disk diffusion analysis against L. monocytogenes. Fractions E and F (eluded between 20 and 30 min) exhibited the most antibacterial activity. There were no differences between solvents used ( p = .05). Further investigation into specific compounds within these extracts will be completed in the future. [ABSTRACT FROM AUTHOR]

RpoS is a key stress-inducible sigma factor that regulates stress resistance genes in Escherichia coli, such as the katE gene encoding catalase HPII and the glg genes encoding glycogen synthesis proteins. Monitoring RpoS activity can provide information on the stress sensitivity of E. coli isolates in clinical settings because the RpoS in these isolates is often mutated. In the present study, we found a novel, missense point mutation at RpoS residue 128 in a clinical Shiga toxin-producing E. coli (STEC) isolate. This mutation caused RpoS dysfunction and increased stress sensitivity. A mutant rpoS was cloned from a clinical STEC that is vulnerable to cold temperature and oxidative stresses. Mutant RpoS protein expression was detected in the clinical isolate, and this RpoS was non-functional according to HPII activity and glycogen levels, which are positively regulated by RpoS and thus are used as indicators for RpoS function. A reporter assay with b-galactosidase indicated that the dysfunction occurred at the transcriptional level of genes regulated by RpoS. Furthermore, substitution analysis indicated that the hydrophobicity of the amino acid at residue 128 was critical for RpoS activity; the simulation analysis indicated that the amino acids of RNA polymerase (RNAP) that interact with RpoS residue 128 are hydrophobic, suggesting that this hydrophobic interaction is critical for RpoS activity. In addition, substitution of Ile128 to Pro128 abolished RpoS activity, possibly as a result of disruption of the secondsary structure around residue 128, indicating that the structure is also a crucial factor for RpoS activity. These results indicate that only one point mutation at a hydrophobic residue of the complex formed during transcription leads to a critical change in RpoS regulation. Moreover, we found that Ile128 is widely conserved among various bacteria: several bacterial strains have Met128 or Leu128, which are hydrophobic residues, and these strains had similar or higher RpoS activity than that observed with Ile128 in this study. These data indicate that the hydrophobicity of the amino acid at residue 128 is critical for RpoS activity and is consequently important for bacterial survival. Taken together, these findings may contribute to a deeper understanding of protein functional mechanisms and bacterial stress responses. [ABSTRACT FROM AUTHOR]

The aim of the present review is to highlight the threats to human health posed by consumption of milk and dairy products. The interest in drinking raw milk has been growing in some societies as many people believe it has health benefits. Raw milk is promoted as 'health food' despite the fact that it poses a realistic microbiological hazard for the consumers' health or life. Food-borne disease outbreaks associated with Campylobacter spp., Salmonella spp., shigatoxin-producing Escherichia coli, Brucella melitensis, Mycobacterium bovis and tick-borne encephalitis virus have been traced to the consumption of raw milk, however, many other microorganisms that can be present in milk are considered as potential food-borne pathogens to humans. The other common causative agents in food-borne disease outbreaks are bacterial toxins produced by Bacillus, Clostridium and Staphylococcus spp. Some of the milk pathogens harbour antimicrobial resistant genes, which can be transferred to commensal bacteria. Most dangerous are methicillin-resistant Staphylococcus aureus and extended spectrum beta lactamase /AmpC gene-carrying bacteria from the family of Enterobacteriaceae, which might negatively affect the treatment of infections in humans. Fungi are not considered as food-borne pathogens for humans, however their secondary metabolites, mycotoxins, constitute a potential threat to public health. Mycotoxins or their metabolites detected so far in milk samples include aflatoxins, ochratoxin A, zearalenone and its metabolites, fumonisins, de-epoxy-deoxynivalenol and cyclopiazonic acid. [ABSTRACT FROM AUTHOR]

The increasing market of probiotics from plant matrices justifies the interest on fermented olives – not only for their nutritional properties, but also because they contain health-promoting phytochemicals (such as phenolic compounds) that exhibit antibacterial, antiproliferative, anticarcinogenic and anti-inflammatory properties. Additionally, olives have proven a good source and carrier of Lactobacillus strains with probiotic characteristics. However, studies focusing on the combined effect of phenolic compounds with wild probiotic bacteria have not been yet carried out. Hence, the aim of this work was to set up the combination of native olive phenolic compounds, e.g. oleuropein and hydroxytyrosol, on the recommended levels for a daily dose of olives containing probiotic bacteria – and their effect on the attachment ability and action against pathogens in situ . Tests on the health benefits of these compounds, viability and adhesion capacity of probiotic bacteria, and consequent biofilm formation, composition and relationship with adhesivity on Caco-2 model were performed. The Caco-2 cell viability results (>140%) show that there is no toxicity effect of both phenolic compounds for the levels considered (0.04 and 0.01%, w/v, for OL and HT, respectively). Conversely, these compounds can inhibit (26–50%) proliferation of human colon adenocarcinoma cells. It became clear that biofilm production on abiotic surfaces is not necessarily associated with adhesivity on biotic surfaces. The strong increase in the adhesion degree of Lactobacillus plantarum 33 after biofilm establishment prompted evaluation of the correlation between biofilm formation and adhesion capacities. [ABSTRACT FROM AUTHOR]

We investigated the combination effect of ohmic heating and pH for inactivation of Escherichia coli O157:H7, Salmonella Typhimurium and Listeria monocytogenes in orange juice. Juice of varying pH (2.5, 3.5, and 4.5) was inoculated with the pathogens and subjected to ohmic heating at different temperatures (50, 55, and 60 °C) for different times (from 0 to 60 s). The reduction of pathogens was higher as treatment temperature and time increased and juice pH decreased. At pH 2.5, populations of E. coli O157:H7 were reduced by > 1.81 log, to below the detection limit within 60, 30, and 20 s at 50, 55, and 60 °C, respectively. S. Typhimurium was reduced by 5.15 log within 60 s at 50 °C and to below the detection limit within 10 s at 55 and 60 °C. L. monocytogenes was little affected at 50 °C but was reduced by 2.15 and 3.37 log after 60 s treatment at 55 and 60 °C. There was a similar pattern of inactivation of the pathogens at pH 3.5 and 4.5. There were no significant quality changes after treatment. In conclusion, our results indicate that ohmic heating can effectively inactivate the pathogens and antimicrobial effect significantly increases when combined with higher acidity. [ABSTRACT FROM AUTHOR]

Atmospheric pressure cold plasma technology is becoming increasingly popular for microbiological decontamination of food and bio-materials. In the present study, afterglow corona discharge air plasma (ACDAP) was used for the inactivation of most common food-borne pathogens, namely pathogenic Escherichia coli , Staphylococcus aureus , Salmonella typhimurium , Bacillus cereus , Listeria monocytogenes , and Vibrio parahaemolyticus . Corona discharge plasma was generated at an output voltage of 20 kV DC, and a frequency of 58 kHz. And, a centrifugal blower that provides an airflow velocity of 2.5 m/s at electrode tip level was used for generating the flowing afterglow of the plasma. During plasma exposure, about 20 °C rise in temperature and a 50% decrease in relative humidity were observed in a treatment chamber within 3 h of exposure. Upon ACDAP exposure, as high as 3.5-log (99.97%) reduction in viable cell counts of tested food pathogens, especially E. coli O157:H7, was observed over a 24-hour exposure. The pathogen inactivation pattern was better explained by using the Singh–Heldman model, which belongs to pseudo-first-order kinetics. In conclusion, ACDAP was shown to be effective for the inactivation of common food-borne pathogens. [ABSTRACT FROM AUTHOR]

Abstract: A novel application of GeXP analyzer was developed for simultaneous detection of six pathogens associated with food poisoning outbreaks, including Salmonella enterica, Escherichia coli O157:H7, Listeria monocytogenes, Staphylococcus aureus, Shigella spp., and Campylobacter jejuni. Chimeric primers containing both microbe- and pMD19-specific sequences were fused to universal sequences resulted in PCR products with intended sizes. The PCR products were separated by capillary electrophoresis and identified by using fluorescence spectrophotometry. Plasmid pMD19-T was added to each reaction as positive control to ascertain the PCR steps and data analysis step of the assay. The results indicate that the GeXP method is both specific and sensitive for the detection of all six food-borne pathogens in a single reaction-without any enrichment step. In conclusion, the GeXP-PCR assay is a rapid, sensitive and high-throughput method for parallel analysis of food-borne pathogens. [Copyright &y& Elsevier]

Abstract: During storage of tomatoes, Rhizopus stolonifer rapidly spreads towards adjacent fruits causing severe economic losses while Escherichia coli may cause serious even life threatening diseases. Chitosan-based materials can be used as edible films or coatings to avoid water loss and microbial spoilage. Waxes and essential oils may also be considered for use as antimicrobial agents in chitosan coating. In this study, various chitosan-based formulations (1%) mixed with beeswax (0.1%), oleic acid (1.0%), and lime or thyme essential oil (0.1%) were tested on tomato at three different maturity stages to control R. stolonifer and E. coli DH5α at storage temperatures of 12 °C and 25 °C. Control fruit were only dipped in water. Overall, fruit were wounded, coated and inoculated. Once the coatings were applied, 20 μl of R. stolonifer spore suspension at 105 spores ml−1 concentration and 35 μl of bacterial solution of E. coli DH5α, at 105 cfu μl−1, concentration, were dispensed over the wounded surface. Experiments were carried out in vitro, at a small scale and at semi commercial level. Overall, the protection effect of coating applications was better against E. coli DH5α than R. stolonifer. For in vitro experiments the best coatings was that of chitosan (1%) + beeswax (0.1%) + lime essential oil (0.1%) since no growth of R. stolonifer and E. coli DH5α took place. Other coating that stopped R. stolonifer growth was that of chitosan (1%) + oleic acid (1%) + lime essential oil (0.1%) while for E. coli DH5α were chitosan (1%) + beeswax (0.1%) + thyme essential oil (1%) and chitosan (1%) + beeswax (0.1%). Observation with an electronic scanning microscope showed distorted mycelia and no development of R. stolonifer sporangiospores, and no growth of E. coli DH5α when both microorganisms were grown on the formulation of chitosan (1%) + beeswax (0.1%) + lime essential oil (0.1%). For E. coli DH5α, this same formulation applied on tomatoes at a small scale and in the semi commercial level completely controlled E. coli DH5α at both storage temperatures. The application of chitosan-based edible coating containing beeswax and lime essential oil is promising to follow since it is an environmentally-friendly alternative to control this important pathogenic microorganism. Export tomato producers might benefit from this nonchemical alternative. [Copyright &y& Elsevier]

The extremely acidic environment of the mammalian stomach not only serves to facilitate food digestion but also acts as a natural barrier against infections of food-borne pathogens. Many pathogenic bacteria, such as enterohemorrhagic Escherichia coli, can breach this host defense and cause severe diseases. These pathogens have evolved multiple intricate strategies to overcome the bactericidal activity of acids. In particular, recent studies have uncovered the central roles of two periplasmic chaperones, HdeA and HdeB, in protecting enteric bacteria from extremely acidic conditions. Here, we review recent advances in the understanding of the acid resistance mechanisms of Gram-negative bacteria and focus on the mechanisms of HdeA and HdeB in preventing acid-induced protein aggregation and facilitating protein refolding following pH neutralization. [ABSTRACT FROM AUTHOR]

The antibacterial effects of Cinnamomum cassia essential oil (EO) and cinnamaldehyde were evaluated against single- and mixed-species cultivation of enteropathogenic Escherichia coli (EPEC) and Listeria monocytogenes attached to stainless steel. A central composite rotational design with two variables and eleven assays was used to optimize the concentrations (0.00-1.00% v/v for the EO and 0.00-0.80% v/v for cinnamaldehyde) and contact times (1-21 min). The models generated were validated, and the effectiveness of C. cassia EO and cinnamaldehyde was compared with that of commercially available chemical sanitizers. Cinnamaldehyde and C. cassia EO proved to be efficient alternatives to commercial chemical sanitizers in the reduction or elimination of sessile bacterial cells. The activity of these natural compounds was, in most cases, equivalent or superior to that of the chemical sanitizers tested. However, L. monocytogenes was more resistant than EPEC to C. cassia EO and cinnamaldehyde, and the bacterial association in mixed-species biofilms made them more susceptible to these compounds. [ABSTRACT FROM AUTHOR]

Abstract: The use of edible films to release antimicrobial constituents in food packaging is a form of active packaging that contributes to extend the shelf-life of a product and provides microbial safety for consumers. A number of plant and animal proteins have been investigated for the production of edible films such as corn zein, wheat gluten, soy and peanut proteins, gelatin, collagen, casein, and whey proteins. Several antimicrobial agents such as organic acids, enzymes, fungicides and natural antimicrobial compounds (spices and essential oils) can be incorporated into edible films. Potassium sorbate (PS) have a long history as a generally recognized as safe food preservative, being widely used to inhibit or retard the growing of a number of recognized food pathogens. Shiga toxin-producing Escherichia coli (STEC) O157 and non-O157 strains have been associated with human disease, ranging from uncomplicated diarrhea to hemorrhagic colitis and hemolytic uremic syndrome. STEC is transmitted to humans through contaminated food, water, and direct contact with infected persons or animals. Several outbreaks caused by non-O157 STEC were described although data implicating these STEC were scanty and the source of infection was not always known. Therefore, the objective of the present study was to incorporate PS into whey protein concentrate (WPC) films and to determine the inhibitory effects of these films against eight non-O157 STEC strains isolated from readyto-eat food samples. [Copyright &y& Elsevier]

Abstract: Herbs and spices containing essential oils (EOs) in the range of 0.05–0.1% have demonstrated activity against pathogens, such as Salmonella typhimurium, Escherichia coli O157:H7, Listeria monocytogenes, Bacillus cereus and Staphylococcus aureus, in food systems. Application of herbs, spices and EOs with antimicrobial effects comparable to synthetic additives is still remote for three major reasons: limited data about their effects in food, strong odor, and high cost. Combinations of techniques have been successfully applied in several in-food and in vitro experiments. This paper aims to review recent in-food applications of EOs and plant-origin natural antimicrobials and recent techniques for screening such compounds. [Copyright &y& Elsevier]

An antimicrobial coating was evaluated in this work for its antimicrobial efficacy against common food-borne pathogens. Dodecyl-di(aminoethyl)-glycine, an organic disinfectant, was immobilized in a silicon oxide matrix to generate thin films over surfaces by means of the sol–gel process. Tetraethoxysilane was used as the polymeric precursor. No alteration of optical transparency on the covered surfaces was observed. Topographic images obtained with atomic force microscopy showed a homogeneous film with no additional roughness added by the polymer to the surface. The attenuated total reflectance-Fourier transform infrared spectral data showed the presence of dodecyl-di(aminoethyl)-glycine in the silicon oxide network after a normal cleaning procedure. The antimicrobial efficacy test was performed by exposing coated slides to suspensions of common food-borne pathogens: Escherichia coli, Staphyloccocus aureus, E. coli O157:H7, Salmonella typhi, S. cholerasuiss, Listeria innocua and L. monocytogenes. The coating activity was not only bacteriostatic but also bactericidal. The percent reduction of viable microorganism exposure over 24 h to the coated surface ranged between 99.5%, for the more resistant gram-positive bacteria, and over 99.999%, for most gram-negative bacteria. The silicon matrix itself did not account for any reduction of viable microbial, even more an increase was observed. [ABSTRACT FROM AUTHOR]

Aims: To determine the occurrence of Shiga toxin-producing Escherichia coli (STEC) O157 and coliform bacteria isolates resistant to antimicrobial agents in dairy herds by examining milk filters and to analyse the influence of management factors and antibiotic use on antimicrobial resistance. Methods and Results: A total of 192 in-line milk filters were sampled on 192 dairy farms in the Czech Republic. Information on feeding, husbandry, production, and antibiotic therapy were obtained by questionnaire. The milk filters were cultured for STEC O157 and coliform bacteria. All recovered isolates were examined for antimicrobial susceptibility and presence of antimicrobial-resistance genes. STEC O157 was detected in four (2%) of the filters. Resistant nonpathogenic E. coli and coliform bacteria isolates with specific genes were detected in 44 (23%) of the filters. Conclusions: The study demonstrated a high prevalence of resistant coliform bacteria in milk filters obtained on Czech dairy farms. Significance and Impact of the Study: The occurrence of resistant coliform bacteria in milk filters was significantly higher among isolates from farms where antibiotic therapy against mastitis was employed during the dry period ( P < 0·05). [ABSTRACT FROM AUTHOR]

Abstract: The effect of gaseous ozone and hot water, alone or in combination, on the sensory and microbial quality of cantaloupe melon was investigated. Escherichia coli O157:H7 transmission from the rind to edible melon flesh during cutting practices was also investigated. Four different treatments consisting of hot water (75°C, 1min), gaseous ozone (10,000ppm, 30min), gaseous ozone supplied by carbon monoxide gas and the combination of hot water and gaseous ozone were evaluated. Sensory quality and growth evolution of aerobic mesophilic and psychrotrophic bacteria, coliforms and molds were studied. In general, hot water, gaseous ozone, and the combination of hot water and gaseous ozone were effective in reducing total microbial population. The combination of hot water and gaseous ozone was the most effective treatment to control microbial growth achieving 3.8, 5.1, 2.2 and 2.3log reductions for mesophilic and psychrotrophic bacteria, molds and coliforms, respectively. However no significant differences were observed between gaseous ozone and gaseous ozone supplied by with carbon monoxide gas. There was no evidence of damage in melons treated with hot water, ozone or their combination and they maintained initial texture and aroma. Therefore, the combination of hot water and gaseous ozone may be an efficient and promising treatment for controlling microbial growth and maintaining sensory quality of melons. [Copyright &y& Elsevier]

Lactic acid bacteria (LAB) are often utilized to control food-borne pathogens on produce and on cooked, fermented, or refrigerated meats. Most research to date has focused on the inhibition of Listeria monocytogenes, Escherichia coli O157:H7, Salmonella, Clostridium botulinum, and spoilage microorganisms. LAB are excellent candidates for reducing pathogen levels on foods because they inhibit the growth of these microorganisms through various mechanisms without causing unacceptable sensory changes. This review provides an up-to-date look at research directed at maximizing the use of LAB by selecting the most appropriate strains, by learning how to apply them to foods most effectively, and by gaining an understanding of the mechanism by which they inhibit pathogens. [ABSTRACT FROM AUTHOR]

Abstract: The Chinese green tea extract was found to strongly inhibit the growth of major food-borne pathogens, Escherichia coli O157:H7, Salmonella Typhimurium DT104, Listeria monocytogenes, Staphylococcus aureus, and a diarrhoea food-poisoning pathogen Bacillus cereus, by 44–100% with the highest activity found against S. aureus and lowest against E. coli O157:H7. A bioassay-guided fractionation technique was used for identifying the principal active component. A simple and efficient reversed-phase high-speed counter-current chromatography (HSCCC) method was developed for the separation and purification of four bioactive polyphenol compounds, epicatechin gallate (ECG), epigallocatechin gallate (EGCG), epicatechin (EC), and caffeine (CN). The structures of these polyphenols were confirmed with mass spectrometry. Among the four compounds, ECG and EGCG were the most active, particularly EGCG against S. aureus. EGCG had the lowest MIC90 values against S. aureus (MSSA) (58mg/L) and its methicilin-resistant S. aureus (MRSA) (37mg/L). Scanning electron microscopy (SEM) studies showed that these two compounds altered bacterial cell morphology, which might have resulted from disturbed cell division. This study demonstrated a direct link between the antimicrobial activity of tea and its specific polyphenolic compositions. The activity of tea polyphenols, particularly EGCG on antibiotics-resistant strains of S. aureus, suggests that these compounds are potential natural alternatives for the control of bovine mastitis and food poisoning caused by S. aureus. [Copyright &y& Elsevier]

Abstract: Numerous virulence factors including adhesins, host cell surface-modifying factors, invasins, toxins, and secretion systems are involved in Escherichia coli pathogenicity mechanisms. Strains of the same pathotype are genetically similar and carry the same virulence determinants which are ideal targets for the determination of the pathogenic potential of any given E. coli isolate. We examined 95 strains of E. coli isolated from two kinds of traditional Slovak cheeses made from raw sheep milk in course of one year. We tested those strains with the goal to determine some of 11 selected genes of virulence factors which at least partially represent all frequent pathotypes of E. coli. Markers of VTEC (VT1,VT2,VT2e), ETEC (ST I,ST II,LT I), EPEC (EaeA), EIEC (Einv), EAEC (Eagg), and UPEC (CNF1,CNF2) were examined using PCR assays. The result of our testing was the determination of nine potentially pathogenic strains from 95 isolates (9.72%). We did not prove VT1 and VT2 factors as well as Einv and Eagg in any strains. We detected ST I in two strains, ST II and LT I in one strain, and VT2e in one strain. In this study most frequent virulence markers were CNF 1 (three strains) and EaeA (three strains). [Copyright &y& Elsevier]

y.s. jung, r.c. anderson, t.r. callaway, t.s. edrington, k.j. genovese, r.b. harvey, t.l. poole and d.j. nisbet. 2004.To test the inhibitory activity of 2-nitro-1-propanol (2NPOH) againstSalmonellaTyphimurium,Escherichia coliO157:H7 andEnterococcus faecalis.Specific growth rates (h−1) ofS. Typhimurium,E. coliO157:H7 andEnt. faecaliswere determined during culture in tryptic soya broth (TSB) supplemented with 0–10 mm2NPOH. Growth rates were inhibited by 2NPOH, with nearly complete inhibition observed with 10 mm. Studies withS. Typhimurium revealed that its survivability during culture in TSB containing 5 or 10 mm2NPOH was lower (P < 0·05) under aerobic than anaerobic conditions. The survivability ofSalmonelladuring anaerobic culture in TSB containing 2·5 mm2NPOH was less at pH 5·6 than at pH 7·0 and 8·0. NoSalmonellasurvived anaerobic incubation in TSB supplemented with 10 mm2NPOH regardless of pH. When incubated in suspensions of freshly collected populations of ruminal and faecal bacteria,Salmonellaconcentrations were lower (P < 0·05) in suspensions containing 10 mm2NPOH than in suspensions containing no 2NPOH.2NPOH inhibitedS. Typhimurium,E. coliO157:H7 andEnt. faecalis.Results suggest that 2NPOH may be a useful antimicrobial supplement to reduce carriage of certain food-borne pathogens in food animals. [ABSTRACT FROM AUTHOR]

To date, there have been no published information and empirical data available on the role played by the food preparer in the domestic kitchen in the Republic of Ireland. In this study, we have looked at the incidence of potential food pathogens and their cross-infection in the domestic kitchen during the preparation of a Sunday roast chicken lunch. Key contact sites in the domestic kitchen were sampled, including the chicken carcass before and after the preparation of a roast chicken meal. Twelve contact sites in twenty-five domestic kitchens were analysed and tested for aerobic plate count, Salmonella, Campylobacter, Escherichia coli and Staphylococcus aureus. Our findings identified the ability of food-borne disease microorganisms to become disseminated from infected foods, such as fresh chickens, to hand and food contact surfaces in the domestic kitchen, reiterating the need for consumer awareness and knowledge of effective hygiene procedures in the domestic kitchen. [Copyright &y& Elsevier]

MacConkey broth purple provides a more efficient method for Most Probable Number estimation for Shigatoxigenic Escherichia coli (E.coli) than the process of bacterial enrichment in buffered peptone water followed by detection on MacConkey agar, since it is a single-step process that gives comparable results in plant extracts. • MPN estimations quantify low concentrations of bacteria, requiring two-step enrichment and detection stages • MacConkey broth purple enables a single-step MPN estimation for Escherichia coli • MacConkey broth purple correctly estimated E. coli O157:H7 numbers from inoculated plant seedlings [ABSTRACT FROM AUTHOR]

Abstract: The production of safe red meat depends on effective control of pathogenic microorganisms at all stages of the “farm-to-fork” chain. Eight microorganisms have been selected as the focus of the PathogenCombat project: Shiga toxin producing Escherichia coli (STEC), Mycobacterium avium subspecies paratuberculosis (Map), Listeria monocytogenes, Campylobacter jejuni, Penicillium nordicum, invasive variants of Saccharomyces cerevisiae, hepatitis E virus and tick borne encephalitis virus. The need and potential for coordinated control of the selected food-borne pathogens by on-farm interventions is assessed using a decision tree and a review of the relevant scientific literature. Control measures to reduce the carriage of these pathogens in ruminants prior to slaughter are reviewed with reference to the current regulations and guidelines relating to the primary production. From the eight pathogens investigated, two (STEC and Map), are likely to be effectively controlled by interventions at farm level and the applicable interventions are described and discussed. Ruminants are the main reservoir for these two pathogens; hence a reduction of carriage in livestock should directly reduce human exposure through the consumption of beef and lamb. [ABSTRACT FROM AUTHOR]