Sporadic Shiga Toxin-Producing Escherichia coli-Associated Pediatric Hemolytic Uremic Syndrome, France, 2012-2021

Shiga toxin-producing Escherichia coli-associated pediatric hemolytic uremic syndrome (STEC-HUS) remains an important public health risk in France. Cases are primarily sporadic, and geographic heterogeneity has been observed in crude incidence rates. We conducted a retrospective study of 1,255 sporadic pediatric STEC-HUS cases reported during 2012-2021 to describe spatiotemporal dynamics and geographic patterns of higher STEC-HUS risk. Annual case notifications ranged from 109 to 163. Most cases (n = 780 [62%]) were in children <3 years of age. STEC serogroups O26, O80, and O157 accounted for 78% (559/717) of cases with serogroup data. We identified 13 significant space-time clusters and 3 major geographic zones of interest; areas of southeastern France were included in >5 annual space-time clusters. The results of this study have numerous implications for outbreak detection and investigation and research perspectives to improve knowledge of environmental risk factors associated with geographic disparities in STEC-HUS in France.

Fatal Meningitis from Shiga Toxin-Producing Escherichia coli in 2 Full-Term Neonates, France

We report fatal meningitis in 2 neonates in France caused by Shiga toxin 1-producing Escherichia coli. Virulence factors capsular K1 antigen and salmochelin were present in both strains, potentially representing a new hybrid pathotype. Clinicians should remain aware of emerging pathotypes and design therapeutic strategies for neonatal E. coli infections.

Factors affecting dialysis duration in children with Shiga toxin-producing Escherichia coli-associated hemolytic uremic syndrome

BACKGROUND

Predicting disease severity can be informative for management of HUS. Dialysis requirement, volume depletion, elevated white blood cell counts, very young age, and use of antimotility agents are known factors associated with severe HUS.

METHODS

A retrospective cohort analysis was performed to identify factors associated with dialysis duration using electronic medical record and chart review of 76 children ≤ 18 years of age at presentation with STEC-HUS identified through billing data from July 2008 to April 2020 at James Whitcomb Riley Hospital for Children, Indiana University, Indiana.

RESULTS

Novel findings associated with prolonged dialysis duration were age ≥ 6 years old at presentation (p = 0.041) and lack of drop in platelets below 60,000/mm3 anytime during the illness (p = 0.015). In addition, children with NSAID exposure trended longer on dialysis: 15 days with vs. 10 days without (p = 0.117). Known risk factors for severe disease including elevated peak white blood cell (WBC) count and higher hematocrit at presentation were also associated with longer dialysis duration: children with peak WBC > 20,000/mm3 were on dialysis for 15 vs. 9.5 days (p = 0.002) and in children on dialysis ≥ 14 days hematocrit at presentation was 29.6% vs. 24.2% (p = 0.03). Children requiring dialysis for 20 days or longer were more likely to be on anti-hypertensive medications (p = 0.025) and have chronic kidney disease at 12-month follow up (p = 0.044).

CONCLUSIONS

Age ≥ 6, elevated WBC count > 20,000/mm3, higher hematocrit at presentation, lack of drop in platelets to < 60,000/mm3, and possibly NSAID exposure during illness are associated with longer dialysis duration in STEC-HUS. A higher resolution version of the Graphical abstract is available as Supplementary information.

Risk Factors for Non-O157 Shiga Toxin-Producing Escherichia coli Infections, United States

Shiga toxin-producing Escherichia coli (STEC) causes acute diarrheal illness. To determine risk factors for non-O157 STEC infection, we enrolled 939 patients and 2,464 healthy controls in a case-control study conducted in 10 US sites. The highest population-attributable fractions for domestically acquired infections were for eating lettuce (39%), tomatoes (21%), or at a fast-food restaurant (23%). Exposures with 10%-19% population attributable fractions included eating at a table service restaurant, eating watermelon, eating chicken, pork, beef, or iceberg lettuce prepared in a restaurant, eating exotic fruit, taking acid-reducing medication, and living or working on or visiting a farm. Significant exposures with high individual-level risk (odds ratio >10) among those >1 year of age who did not travel internationally were all from farm animal environments. To markedly decrease the number of STEC-related illnesses, prevention measures should focus on decreasing contamination of produce and improving the safety of foods prepared in restaurants.

Microbiological Quality of Ready-to-Eat Salad Products Collected from Retail and Catering Settings in England during 2020 to 2021

ABSTRACT

Salad and other fresh produce were collected in England from retail and catering businesses during 2020 to 2021 and were tested for Salmonella, Shiga toxin-producing Escherichia coli (STEC), Listeria, Bacillus cereus, and E. coli. Of the 604 samples collected, 57% were from retail settings and 43% were from catering settings; 61% were either salad leaves or salad leaves mixed with other products. Equal numbers of samples were prepacked or loose, and 50% were refrigerated at the time of sampling. Combining results for all microbiological parameters, 84% were interpreted as satisfactory, 12% were interpreted as borderline, and 4% were interpreted as unsatisfactory. One sample (prepacked leaves, cucumber, and tomato from a caterer) was categorized as unacceptable and potentially injurious because of detection of STEC O76; no STEC from human infections in the United Kingdom matched this isolate. No Salmonella enterica was detected, but Listeria monocytogenes was recovered from 11 samples: 1 at 20 CFU/g and the remainder at <20 CFU/g. B. cereus was detected at borderline levels (103 to ≤105 CFU/g) in 9% of samples and at an unsatisfactory level (>105 CFU/g) in one sample. E. coli was detected in 3% of samples at borderline levels (20 to ≤102 CFU/g) and in 4% at unsatisfactory levels (>102 CFU/g). There was a significant association between detection of L. monocytogenes and borderline or unsatisfactory levels of E. coli. There were no specific risk profiles associated with products with the higher levels of B. cereus, STEC, or Listeria, but elevated levels of E. coli were predominantly confined to loose products from the United Kingdom collected from caterers in summer or autumn 2021 and may have resulted from relaxation of COVID-19 restrictions. Among the L. monocytogenes isolates, only one matched those from human cases and was recovered from a prepacked mixed salad from a catering business in 2021. This isolate was the same strain as that responsible for a multicountry outbreak (2015 to 2018) associated with Hungarian-produced frozen sweet corn; no link to the outbreak food chain was established.

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Public Health Risk of Foodborne Pathogens in Edible African Land Snails, Cameroon

In tropical countries, land snails are an important food source; however, foodborne disease risks are poorly quantified. We detected Campylobacter spp., Yersinia spp., Listeria spp., Salmonella spp., or Shiga-toxigenic Escherichia coli in 57%-86% of snails in Cameroon. Snail meat is a likely vector for enteric diseases in sub-Saharan Africa countries.

Impact of Chlorinated Water on Pathogen Inactivation during Wheat Tempering and Resulting Flour Quality

ABSTRACT

Outbreaks of enteric pathogens linked to wheat flour have led the wheat milling industry to seek solutions addressing this food safety concern. Chlorinated water at 400 to 700 ppm has been used in the flour milling industry as a tempering aid to control growth of yeast and mold in tempering bins. However, the effectiveness of chlorinated water for inactivating enteric pathogens on wheat kernels was unknown. Five strains of Shiga toxin-producing Escherichia coli and two strains of Salmonella were inoculated onto hard red spring wheat at 7 log CFU/g and stored at room temperature for 1 month. Inoculated wheat was tempered with four concentrations (0, 400, 800, and 1,200 ppm) of chlorinated water (pH 6.5). The reduction due to chlorine was determined by calculating change in microbial loads at each chlorine level by using the response at 0 ppm as a reference. Uninoculated wheat tempered with chlorinated water was used to measure flour quality parameters. Changes in pathogen population over 18 h ranged from -2.35 to -0.30 log CFU/g with 800 ppm of chlorinated water and were not significantly different from changes at 400 and 1,200 ppm. Significant (P < 0.05) differences in the extent of reduction were observed among strains. However, the effect of chlorinated water at reducing native microbes on wheat kernels was minimal, with an average reduction of 0.39 log CFU/g for all concentrations. No significant (P > 0.05) changes occurred in flour quality and gluten functionality or during bread making for grains tempered at 400 and 800 ppm of chlorinated water. There were small but significant (P < 0.05) changes in flour protein content, final viscosity, and water absorption when tempered with 1,200 ppm of chlorinated water. The data showed that the level of chlorinated water currently used in industry for tempering could reduce enteric pathogen numbers by 1.22 log CFU/g for Shiga toxin-producing Escherichia coli and 2.29 log CFU/g for Salmonella, with no significant effects on flour quality and gluten functionality.

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Viability of Shiga Toxin-Producing Escherichia coli, Salmonella spp., and Listeria monocytogenes during Preparation and Storage of Fuet, a Traditional Dry-Cured Spanish Pork Sausage

ABSTRACT

The primary objective of this study was to monitor viability of Shiga toxin-producing Escherichia coli (STEC), Salmonella spp., and Listeria monocytogenes during preparation and storage of fuet. Regarding methodology, coarse-ground pork (ca. 35% fat) was mixed with salt (2.5%), dextrose (0.3%), starter culture (ca. 7.0 log CFU/g), celery powder (0.5%), and ground black pepper (0.3%) and then separately inoculated with a multistrain cocktail (ca. 7.0 log CFU/g) of each pathogen. The batter was stuffed into a ca. 42-mm natural swine casing and fermented at 23 ± 2°C and ca. 95% ± 4% relative humidity to ≤pH 5.3 (≤48 h). Sausages were then dried at 12 ± 2°C and ca. 80% ± 4% relative humidity to a water activity (aw) of 0.89 (within 33 days) or aw 0.86 (within 60 days). A portion of each batch of fuet was subjected to high-pressure processing (HPP; 600 MPa for 3 min) before chubs were vacuum packaged and stored for 30 days at 20 ± 2°C. The results revealed that pathogen numbers remained relatively unchanged after fermentation (≤0.35 log CFU/g reduction), whereas reductions of ca. 0.8 to 3.2 log CFU/g were achieved after drying fuet to aw 0.89 or 0.86. Regardless of whether fuet was or was not pressure treated, additional reductions of ca. 2.2 to ≥5.3 log CFU/g after drying were achieved following 30 days of storage at 20°C. For non-HPP-treated fuet dried to aw 0.89 and stored for 30 days at 20°C, total reductions of ≥5.3 log CFU/g in levels of STEC or Salmonella spp. were achieved, whereas levels of L. monocytogenes were reduced by ca. 3.6 log CFU/g. Total reductions of ≥5.3 log CFU/g in levels of all three pathogens were achieved after drying non-HPP-treated fuet to aw 0.86. For fuet dried to aw 0.89 or 0.86, that were pressure treated and then stored for 30 days at 20°C, total reductions of >6.2 log CFU/g in levels of all three pathogens were achieved. In conclusion, the processing parameters tested herein, with or without application of HPP, validated that reductions of ≥2.0 or ≥5.0 log CFU/g in levels of STEC, Salmonella spp., and L. monocytogenes were achieved during preparation and storage of fuet.

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Using Outbreak Data for Hypothesis Generation: A Vehicle Prediction Tool for Disease Outbreaks Caused by Salmonella and Shiga Toxin-Producing Escherichia coli

Hypothesis generation about potential food and other exposures is a critical step in an enteric disease outbreak investigation, helping to focus investigation efforts and use of limited resources. Historical outbreak data are an important source of information for hypothesis generation, providing data on common food- and animal-pathogen pairs and other epidemiological trends. We developed a model to predict vehicles for Shiga toxin-producing Escherichia coli and Salmonella outbreaks using demographic and outbreak characteristics from outbreaks in the Centers for Disease Control and Prevention's Foodborne Disease Outbreak Surveillance System (1998-2019) and Animal Contact Outbreak Surveillance System (2009-2019). We evaluated six algorithmic methods for prediction based on their ability to predict multiple class probabilities, selecting the random forest prediction model, which performed best with the lowest Brier score (0.0953) and highest accuracy (0.54). The model performed best for outbreaks transmitted by animal contact and foodborne outbreaks associated with eggs, meat, or vegetables. Expanding the criteria to include the two highest predicted vehicles, 83% of egg outbreaks were predicted correctly, followed by meat (82%), vegetables (74%), poultry (67%), and animal contact (62%). The model performed less well for fruit and poultry vehicles, and it did not predict any dairy outbreaks. The final model was translated into a free, publicly available online tool that can be used by investigators to provide data-driven hypotheses about outbreak vehicles as part of ongoing outbreak investigations. Investigators should use the tool for hypothesis generation along-side other sources, such as food-pathogen pairs, descriptive data, and case exposure assessments. The tool should be implemented in the context of individual outbreaks and with an awareness of its limitations, including the heterogeneity of outbreaks and the possibility of novel food vehicles.

Occurrence of the Seven Most Common Serotypes of Shiga Toxin-Producing Escherichia coli in Beef Cuts Produced in Meat Processing Plants in the State of São Paulo, Brazil

ABSTRACT

Healthy cattle are considered the main reservoir of Shiga toxin-producing Escherichia coli (STEC) strains, so in some places in the world, products derived from beef are the most common source for disease outbreaks caused by these bacteria. Therefore, to guarantee that the beef produced by our slaughterhouses is safe, there is a need for continuous monitoring of these bacteria. In this study, 215 beef cuts were evaluated, including chilled vacuum-packed striploins (151 samples), rib eyes (30 samples), and knuckles (34 samples), from March to June 2018. These meat samples were collected from the slaughter of unconfined cattle, being arbitrarily collected from eight meat processing companies in São Paulo state, Brazil. Each sample was examined for the presence of STEC toxin type (stx1 and/or stx2 genes) and also the attaching and effacing E. coli (eae) gene, determined by a multiplex PCR assay. We show that the major seven STEC strains (O serogroups O26, O45, O103, O111, O121, O145, and O157) are not detected in any of the analyzed beef cut samples; however, three of them presented the virulence eae gene. Therefore, the absence of STEC strains in the beef samples may be an indication of the low prevalence of this pathogen in the cattle herd on the farm, associated with good hygiene and handling practices adopted by the meat industry.

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Consumption of Raw Flour in the United States: Results from the 2019 U.S. Food and Drug Administration Food Safety and Nutrition Survey

ABSTRACT

Several outbreaks of Shiga toxin-producing Escherichia coli infections in the past decade have been linked to flour and flour-associated products and have raised concerns that the consumption of raw flour represents a public health risk as a vehicle for foodborne pathogens. The extent to which consumers know and understand that they should not consume raw flour is unclear. In fall 2019, the U.S. Food and Drug Administration collected data on perceptions regarding uncooked flour and on self-reported consumption behaviors via the Food Safety and Nutrition Survey, a national probability survey of U.S. adults (≥18 years of age). Cross-tabulations and regressions were used to analyze the data (n = 2,171). Thirty-five percent of consumers reported having tasted or eaten something with uncooked flour in it in the previous 12 months. Responses differed significantly by sex, race, education, and age. On average, respondents indicated that uncooked flour is not likely to contain germs that can make people sick, with significant differences noted by demographic categories. Respondents rated raw homemade cookie dough as moderately likely to have germs that can make people sick, with significant demographic differences. These findings indicate that U.S. consumers are largely unaware that raw flour is risky to consume, and many people are consuming products that contain raw flour.

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Prevalence of Shiga Toxin-Producing Escherichia coli and Salmonella in Native Pecan Orchards as Influenced by Waiting Periods between Grazing and Harvest

ABSTRACT

Animals (grazing, working, or intrusion) in produce production areas may present a potential contamination source of foodborne pathogens on produce. Cattle grazing on native pecan production orchards, a common practice in the southern United States, provides an opportunity to study the impact of grazing practice and waiting periods on contamination rates of foodborne pathogens of tree nuts. Therefore, the objective of this study was to determine the prevalence of Salmonella and Shiga toxin-producing Escherichia coli (STEC) in native pecan production orchards as influenced by waiting periods between grazing cattle and pecan harvest. Soil (10 g), cattle feces (10 g), and in-shell pecans (25 g) were sampled from five cattle-grazed orchards in areas with cattle removed 2 or 4 months before harvest and not removed. Five nongrazing orchards were sampled at harvest for comparison. Detection and isolation of the pathogens were performed by enrichment, selective isolation, and multiplex PCR. Statistical analyses were performed using contingency tables with Pearson's chi-square test. The prevalence of STEC (36%) and Salmonella (29%) in cattle-grazed orchards was significantly higher than in nongrazed orchards (13 and 7%, respectively). STEC prevalence in cattle-grazed orchards was higher (38%) in areas with cattle at harvest than in fenced areas where cattle were removed 2 (29%) and 4 (27%) months before harvest. Salmonella prevalence was similar in areas without fencing (31%) and areas with cattle removed at 2 (22%) and 4 (30%) months before harvest. However, there were no significant differences (P > 0.05) in contamination rates between waiting periods for either pathogen, suggesting a limited impact of waiting periods on reducing the risk of contamination.

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A Review of Significant European Foodborne Outbreaks in the Last Decade

ABSTRACT

Foodborne diseases remain a global public health challenge worldwide. The European surveillance system of multistate foodborne outbreaks integrates elements from public and animal health and the food chain for early detection, assessment, and control. This review includes descriptions of the significant outbreaks that occurred in Europe in the last decade. Their significance and relevance to public health is derived from the changes, improvements, and novelties that pushed toward building a safer food system in the European Union, certainly driven by the One Health approach. In 2011, a point source monoclonal outbreak of infections caused by Escherichia coli serotype O104:H4 in sprouted seeds resulted in hundreds of cases of hemolytic uremic syndrome and several fatalities. In 2015, a prolonged outbreak of Listeria monocytogenes infections caused by contamination of frozen corn in Europe resulted in 47 cases and nine deaths. In 2016, a persistent polyclonal outbreak of Salmonella Enteritidis was linked to the consumption of eggs and was associated with hundreds of cases. The outbreak evaluations highlight the importance of rapid sharing of data (e.g., sequencing and tracing data) and the need for harmonizing bioinformatics outputs and computational approaches to facilitate detection and investigation of foodborne illnesses. These outbreaks led to development of a legal framework for a European collaboration platform for sharing whole genome sequence data and enabled the enforcement of existing hygiene and food safety provisions and the development of new hygiene guidelines and best practices. This review also briefly touches on the new trends in information technologies that are being explored for food traceability and safety. These technologies could enhance the traceability of food throughout the supply chain and redirect the conventional tracing system toward a digitized supply chain.

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Shiga Toxin-Producing Escherichia coli (STEC) and STEC-Associated Virulence Genes in Raw Ground Pork in Canada

ABSTRACT

Shiga toxin-producing Escherichia coli (STEC) O157:H7/nonmotile and some non-O157 STEC strains are foodborne pathogens. In response to pork-associated O157 STEC outbreaks in Canada, we investigated the occurrence of STEC in Canadian retail raw ground pork during the period of 1 November 2014 to 31 March 2016. Isolated STEC strains were characterized to determine the Shiga toxin gene (stx) subtype and the presence of virulence genes encoding intimin (eae) and enterohemorrhagic E. coli hemolysin (hlyA). O157 STEC and non-O157 STEC strains were isolated from 1 (0.11%) of 879 and 13 (2.24%) of 580 pork samples, respectively. STEC virulence gene profiles containing both eae and hlyA were found only in the O157 STEC (stx2a, eae, hlyA) isolate. The eae gene was absent from all non-O157 STEC isolates. Of the 13 non-O157 STEC isolates, two virulence genes of stx1a and hlyA were found in four (30.8%) O91:H14 STEC isolates, whereas one virulence gene of stx2e, stx1a, and stx2a was identified in five (38.5%), two (15.4%), and one (7.7%) STEC isolates, respectively, of various serotypes. The remaining non-O157 STEC isolate carried stx2, but the subtype is unknown because this isolate could not be recovered for sequencing. O91:H14 STEC (stx1a, hlyA) was previously reported in association with diarrheal illnesses, whereas the other non-O157 STEC isolates identified in this study are not known to be associated with severe human illnesses. Virulence gene profiles identified in this study indicate that the occurrence of non-O157 STEC capable of causing severe human illness is rare in Canadian retail pork. However, O157 STEC in ground pork can occasionally occur; therefore, education regarding the potential risks associated with STEC contamination of pork would be beneficial for the public and those in the food industry to help reduce foodborne illnesses.

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Determination and validation of D-values for Listeria monocytogenes and Shiga toxin-producing Escherichia coli in cheese milk

Certain cheeses can be legally produced in the United States using raw milk, but they must be aged for at least 60 d to reduce pathogen risks. However, some varieties, even when aged for 60 d, have been shown to support growth of Listeria monocytogenes or survival of Shiga toxin-producing Escherichia coli (STEC). Thermization, as a subpasteurization heat treatment, has been proposed as a control to reduce the risk of pathogens in raw cheese milk while retaining some quality attributes in the cheese. However, the temperature and time combinations needed to enhance safety have not been well characterized. The objective of this research was to determine and validate decimal reduction values (D-values) for L. monocytogenes and STEC at thermization temperatures 65.6, 62.8, and 60.0°C; a D-value at 57.2°C was also determined for L. monocytogenes only. Nonhomogenized, pasteurized whole-milk samples (1 mL) were inoculated with 8-log cfu/mL L. monocytogenes or STEC (5- or 7-strain mixtures, respectively), vacuum-sealed in moisture-impermeable pouches, and heated via water bath submersion. Duplicate samples were removed at appropriate intervals and immediately cooled in an ice bath. Surviving bacteria were enumerated on modified Oxford or sorbitol MacConkey overlaid with tryptic soy agar to aid in the recovery of heat-injured cells. Duplicate trials were conducted, and survival data were used to calculate thermal inactivation rates. D_65.6°C-, D_62.8°C-, and D_60.0°C-values of 17.1 and 7.2, 33.8 and 16.9, and 146.6 and 60.0 s were found for L. monocytogenes and STEC, respectively, and a D_57.2°C-value of 909.1 s was determined for L. monocytogenes. Triplicate validation trials were conducted for each test temperature using 100 mL of milk inoculated with 3 to 4 log cfu/mL of each pathogen cocktail, A 3-log reduction of each pathogen was achieved faster in larger volumes than what was predicted by D-values (D-values were fail-safe). Data were additionally compared with published results from 21 scientific studies investigating L. monocytogenes and STEC in whole milk heated to thermization temperatures (55.0-71.7°C). These data can be used to give producers of artisanal raw-milk cheese flexibility in designing thermal processes to reduce L. monocytogenes and STEC populations to levels that are not infectious to consumers.

An Overview of Traceback Investigations and Three Case Studies of Recent Outbreaks of Escherichia coli O157:H7 Infections Linked to Romaine Lettuce

ABSTRACT

Leafy greens contaminated with Shiga toxin-producing Escherichia coli have continued to cause foodborne illness outbreaks in recent years and present a threat to public health. An important component of foodborne illness outbreak investigations is determining the source of the outbreak vehicle through traceback investigations. The U.S. Food and Drug Administration is home to traceback investigation experts who use a standardized process to initiate, execute, and interpret the results of traceback investigations in collaboration with the Centers for Disease Control and Prevention and state and local partners. Traceback investigations of three outbreaks of Shiga toxin-producing E. coli infections linked to romaine lettuce in 2018 and 2019 were examined to demonstrate challenges, limitations, and opportunities for improvement. The three outbreaks resulted in a total of 474 illnesses, 215 hospitalizations, and 5 deaths. These illnesses were linked to the consumption of romaine lettuce from three distinct growing regions in Arizona and California. Some of the challenges encountered included the time it took to initiate a traceback, limited product-identifying information throughout the supply chain, lack of interoperability in record-keeping systems, and comingling of product from multiple suppliers. These challenges led to time delays in the identification of the farm source of the leafy greens and the inability to identify the root cause of contamination. Implementation of technology-enabled traceability systems, testing of these systems, and future regulations to incentivize adoption of traceability systems are some of the initiatives that will help address these challenges by improving traceback investigations and ultimately preventing foodborne illnesses and future outbreaks from occurring.

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Survival of Salmonella and Shiga Toxin-Producing Escherichia coli and Changes in Indigenous Microbiota during Fermentation of Home-Brewed Kombucha

ABSTRACT

Survival and growth of Salmonella and Shiga toxin-producing Escherichia coli (STEC) were investigated in kombucha prepared from four brands of commercially available kombucha kits intended for use by home brewers. Changes in populations of the indigenous microbiota responsible for fermentation of kombucha were also determined. An initial population of Salmonella (6.77 log CFU/mL) decreased to below the detection limit (0.30 log CFU/mL) within 10 days in kombucha prepared from two of the test brands. Populations of 1.85 and 1.20 log CFU/mL were detected in two brands fermented for 14 days. An initial STEC population of 7.02 log CFU/mL decreased to <0.30 log CFU/mL in two brands within 14 days; 0.77 and 0.87 log CFU/mL were detected in kombucha prepared from the other two brands. Salmonella and STEC increased within 1 day in three brands of base tea used to prepare kombucha and were stable throughout 14 days of incubation. Both pathogens steadily declined in base tea prepared from one brand of kombucha kit. Inactivation of the pathogens occurred as the pH of the kombucha decreased, but a clear correlation between rates of inactivation among different brands of kits and decrease in pH was not evident. Growth and peak populations of mesophilic aerobic microorganisms, yeasts, lactic acid bacteria, and acetic acid bacteria varied depending on the kombucha kit brand. No strong evidence was found of a correlation between the behavior of Salmonella or STEC and that of any of these groups of indigenous microbiota. Results of this study show that survival of Salmonella and STEC in kombucha and base tea used to prepare kombucha is dependent on inherent differences in commercially available kombucha kits intended for use in home settings. Strict application of hygienic practices is essential for preventing contamination with Salmonella or STEC and reducing the risk of illness associated the consumption of kombucha.

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Whole-Genome Sequencing of Shiga Toxin-Producing Escherichia coli OX18 from a Fatal Hemolytic Uremic Syndrome Case

We report a fatal case of hemolytic uremic syndrome with urinary tract infection in Japan caused by Shiga toxin–producing Escherichia coli. We genotypically identified the isolate as OX18:H2. Whole-genome sequencing revealed 3 potentially pathogenic lineages (OX18:H2, H19, and H34) that have been continuously isolated in Japan.

Genomic Characterization of hlyF-positive Shiga Toxin-Producing Escherichia coli, Italy and the Netherlands, 2000-2019

Shiga toxin–producing Escherichia coli (STEC) O80:H2 has emerged in Europe as a cause of hemolytic uremic syndrome associated with bacteremia. STEC O80:H2 harbors the mosaic plasmid pR444_A, which combines several virulence genes, including hlyF and antimicrobial resistance genes. pR444_A is found in some extraintestinal pathogenic E. coli (ExPEC) strains. We identified and characterized 53 STEC strains with ExPEC-associated virulence genes isolated in Italy and the Netherlands during 2000–2019. The isolates belong to 2 major populations: 1 belongs to sequence type 301 and harbors diverse stx₂ subtypes, the intimin variant eae-ξ, and pO157-like and pR444_A plasmids; 1 consists of strains belonging to various sequence types, some of which lack the pO157 plasmid, the locus of enterocyte effacement, and the antimicrobial resistance–encoding region. Our results showed that STEC strains harboring ExPEC-associated virulence genes can include multiple serotypes and that the pR444_A plasmid can be acquired and mobilized by STEC strains.

Shiga Toxin-Associated Hemolytic Uremic Syndrome in Adults, France, 2009-2017

We conducted a retrospective study on hemolytic uremic syndrome caused by Shiga toxin–producing Escherichia coli (STEC) in 96 adults enrolled in the cohort of the National Reference Center for Thrombotic Microangiopathies network in France during 2009–2017. Most infections were caused by STEC strains not belonging to the O157 or O104 serogroups. Thirty (31.3%) patients had multiple risk factors for thrombotic microangiopathy. In total, 61 (63.5%) patients required dialysis, 50 (52.1%) had a serious neurologic complication, 34 (35.4%) required mechanical ventilation, and 19 (19.8%) died during hospitalization. We used multivariate analysis to determine that the greatest risk factors for death were underlying immunodeficiency (hazard ratio 3.54) and severe neurologic events (hazard ratio 3.40). According to multivariate analysis and propensity score-matching, eculizumab treatment was not associated with survival. We found that underlying conditions, especially immunodeficiency, are strongly associated with decreased survival in adults who have hemolytic uremic syndrome caused by STEC.

Association between Shiga Toxin-Producing Escherichia coli O157:H7 stx Gene Subtype and Disease Severity, England, 2009-2019

Signs and symptoms of Shiga toxin–producing Escherichia coli (STEC) serogroup O157:H7 infection range from mild gastrointestinal to bloody diarrhea and hemolytic uremic syndrome (HUS). We assessed the association between Shiga toxin gene (stx) subtype and disease severity for »3,000 patients with STEC O157:H7 in England during 2009–2019. Odds of bloody diarrhea, HUS, or both, were significantly higher for patients infected with STEC O157:H7 possessing stx2a only or stx2a combined with other stx subtypes. Odds of severe signs/symptoms were significantly higher for isolates encoding stx2a only and belonging to sublineage Ic and lineage I/II than for those encoding stx2a only and belonging to sublineage IIb, indicating that stx2a is not the only driver causing HUS. Strains of STEC O157:H7 that had stx1a were also significantly more associated with severe disease than strains with stx2c only. This finding confounds public health risk assessment algorithms based on detection of stx2 as a predictor of severe disease.

Acute peritoneal dialysis, complications and outcomes in 389 children with STEC-HUS: a multicenter experience

BACKGROUND

Management of acute kidney injury (AKI) in children with hemolytic uremic syndrome induced by a Shiga toxin-producing Escherichia coli infection (STEC-HUS) is supportive; however, 40 to 60% of cases need kidney replacement therapy (KRT). The aim of this study was to analyze procedure complications, especially peritonitis, and clinical outcomes in children with AKI secondary to STEC-HUS treated with acute PD.

METHODS

This is a multicenter retrospective study conducted among thirty-seven Argentinian centers. We reviewed medical records of 389 children with STEC-HUS hospitalized between January 2015 and February 2019 that required PD.

RESULTS

Complications associated with PD were catheter malfunction (n = 93, 24%), peritonitis (n = 75, 19%), fluid leaks (n = 45, 11.5%), bleeding events (n = 23, 6%), and hyperglycemia (n = 8, 2%). In the multivariate analysis, the use of antibiotic prophylaxis was independently associated with a decreased risk of peritonitis (hazard ratio 0.49, IC 95% 0.29-0.81; p = 0.001), and open-surgery catheter insertion was independently associated with a higher risk (hazard ratio 2.8, IC 95% 1.21-6.82; p = 0.001). Discontinuation of PD due to peritonitis, severe leak, or mechanical complications occurred in 3.8% of patients. No patient needed to be transitioned to other modality of KRT due to inefficacy of the technique. Mortality during the acute phase occurred in 2.8% patients due to extrarenal complications (neurological and cardiac involvement), not related to PD.

CONCLUSIONS

Acute PD was a safe and effective method to manage AKI in children with STEC-HUS. Prophylactic antibiotics prior to insertion of the PD catheter should be considered to decrease the incidence of peritonitis.

Microbiological Survey of Wheat Flour Sold at Retail in Canada, 2018 to 2019

ABSTRACT

Following two O121 Shiga toxin-producing Escherichia coli (STEC) outbreaks linked to wheat flour, this study was conducted to gain baseline information on the occurrence of bacterial pathogens and levels of indicator organisms in wheat flour in Canada. A total of 347 prepackaged wheat flour samples were analyzed for Salmonella species, STEC, Listeria monocytogenes, aerobic colony count (ACC), total coliforms, and Escherichia coli. Salmonella spp. and O157 STEC were not detected in any of the samples. L. monocytogenes was identified in two samples (0.6%) at levels below the limit of detection (<0.7 log CFU/g). Non-O157 STEC were isolated from six samples (1.7%) and were characterized for the presence of STEC virulence genes: stx1, stx2, and their subtypes, eae, hlyA, and aggR. One O103:H25 STEC isolate carried virulence genes (stx1a+eae) that are known to be capable of causing diarrhea and/or bloody diarrhea in humans. Of the five remaining non-O157 STEC isolates, four carried single stx2a or stx2c genes and were considered to have the potential of causing diarrhea. The remaining non-O157 STEC isolate (stx2), while not a priority non-O157 STEC, was not available for sequencing; thus, its potential to cause illness is unknown. ACC, total coliforms, and E. coli were detected (≥0.48 log CFU/g) in 98.8, 72.6, and 0.6% of the flour samples. The mean counts of ACC were greater in whole wheat flour compared with the other flour types tested (P < 0.001). The results of this study suggest that the occurrence of O157 STEC and Salmonella is low but that the occurrence of non-O157 STEC in wheat flour with the potential to cause human illness of diarrhea is relatively common. Therefore, the consumption of raw flour could increase the likelihood of STEC infections. Further research is merited for potential risk mitigation strategies within the food production system and with consumers.

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Effects of Antimicrobial Interventions on Indicator Organisms during Beef Carcass Dressing

ABSTRACT

Beef slaughter establishments employ many interventions to help minimize the occurrence of pathogens in their products. This study explored the effectiveness of various common interventions on microbial load using the results of the Beef-Veal Carcass Baseline Survey conducted in 2014 to 2015. The Food Safety and Inspection Service analyzed swab samples taken from 1,135 carcasses at 139 establishments. These included paired samples from post-hide removal (before evisceration) and prechill (after evisceration). Samples were tested for pathogens (Salmonella and Shiga toxin-producing Escherichia coli) and indicators (E. coli, Enterobacteriaceae, coliforms, and aerobic count [AC]). The sample size for pathogen-positive samples was small, impeding the establishment of a direct correlation between interventions and pathogens. However, we observed associations between pathogen-positive rate and log AC, indicating similar intervention effectiveness of pathogens and indicators in this study. Generally, the use of interventions reduced indicator concentrations. Each intervention produced a range of effectiveness, suggesting that how interventions are applied may be as important as which interventions are applied. The range of effectiveness for single interventions was a 0.4- to 1.9-log AC reduction; for multihurdle interventions, it ranged from 1.6- to 2.9-log AC reduction. The results of this study may be used by slaughter establishments to help identify effective intervention options for pathogen reduction.

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Shiga toxin-producing Escherichia coli isolated from pasteurized dairy products from Bahia, Brazil

The presence of pathogenic Shiga toxin-producing Escherichia coli (STEC) in dairy products represents a public health concern because of its ability to produce the toxins Stx1 and Stx2, which cause intestinal diseases. Monitoring the stages of milk production and checking dairy products for contamination are crucial steps to ensure dairy safety. This study aimed to report the occurrence of thermotolerant coliforms, E. coli, and STEC strains in pasteurized dairy products and to evaluate the antibiotic resistance profiles, serotypes, and characterizations of the STEC isolates by pulsed-field gel electrophoresis. We obtained a total of 138 pasteurized dairy products from 15 processing plants in Bahia, Brazil, to examine coliforms, E. coli, and STEC strains. We found that 43% of samples (59/138) contained thermotolerant coliforms, and 30% (42/138) did not comply with Brazilian regulations. Overall, 6% (9/138) were positive for E. coli and 4% (5/138) were positive for STEC. We recovered 9 STEC isolates from pasteurized cream (2/9), Minas Padrão cheese (2/9), Minas Frescal cheese (4/9), and ricotta (1/9). All isolates were stx2-positive, and 2 were eae-positive. All isolates were negative for the "big 6" STEC serogroups, belonging instead to serotypes ONT:HNT, ONT:H12, O148:H-, OR:H40, OR:HNT, and O148:HNT. Pulsed-field gel electrophoresis revealed 100% genetic similarity among 3 isolates from 2 different samples produced in the same production facility, which may suggest cross-contamination. As well, we found isolates that were 98% similar but in samples produced in different production facilities, suggesting a mutual source of contamination or a circulating strain. Two STEC strains exhibited resistance to streptomycin. Although the isolates presented a low resistance profile and no strain belonged to the "big 6" pathogenic group, the circulation of stx2-positive STEC strains in ready-to-eat products highlights the importance of epidemiological surveillance inside the Brazilian dairy chain.

Reducing Pathogenic Escherichia coli Surrogates on Fresh Beef Cuts by Water-Reducing Antimicrobial Interventions

ABSTRACT

Water use for antimicrobial intervention application for beef harvest has come under increased scrutiny in recent years in an effort to enhance water conservation during beef harvest and fabrication. We determined the efficacy of beef safety interventions for reducing surrogates of the Shiga toxin-producing Escherichia coli (STEC) on beef cuts while lowering intervention-purposed water use for a small or very small beef establishment. Beef briskets, shoulder/clods, and rounds were inoculated with a gelatin-based slurry containing 6.8 ± 0.3 log CFU/g of nonpathogenic E. coli. After 30 min of attachment, inoculated cuts were treated by conventional lactic acid spray (2.5%, 55°C), lactic acid delivered by an electrostatic spray (2.5%, 55°C) handheld wand, hot water spray (82°C), or recycled hot water spray (82°C), wherein previously applied hot water was collected, thermally pasteurized to 82°C, or left untreated. One hundred milliliters of each treatment was sprayed onto marked surfaces of inoculated cuts, after which time surviving surrogate E. coli were enumerated. Lactic acid spray and electrostatic spray treatments produced greater reductions (1.0 to 1.1 log CFU/300 cm2) than hot water interventions (0.3 to 0.5 log CFU/300 cm2) (P ≤ 0.0001). Recycling of water reduced water losses by no less than 45% on recycled hot water spray-treated beef cuts. Low water beef safety interventions offer small and very small inspected beef establishments opportunities to incrementally reduce water use during intervention application, but not necessarily without loss of pathogen reduction efficacy.

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Recovery Rate of Cells of the Seven Regulated Serogroups of Shiga Toxin-Producing Escherichia coli from Raw Veal Cutlets, Ground Veal, and Ground Beef from Retail Stores in the Mid-Atlantic Region of the United States

ABSTRACT

A total of 482 veal cutlet, 555 ground veal, and 540 ground beef samples were purchased from retail establishments in the mid-Atlantic region of the United States over a noncontiguous 2-year period between 2014 and 2017. Samples (325 g each) were individually enriched and screened via real-time PCR for all seven regulated serogroups of Shiga toxin-producing Escherichia coli (STEC). Presumptive STEC-positive samples were subjected to serogroup-specific immunomagnetic separation and plated onto selective media. Up to five isolates typical for STEC from each sample were analyzed via multiplex PCR for both the virulence genes (i.e., eae, stx1 and/or stx2, and ehxA) and serogroup-specific gene(s) for the seven regulated STEC serogroups. The recovery rates of non-O157 STEC from veal cutlets (3.94%, 19 of 482 samples) and ground veal (7.03%, 39 of 555 samples) were significantly higher (P < 0.05) than that from ground beef (0.93%, 5 of 540 samples). In contrast, only a single isolate of STEC O157:H7 was recovered; this isolate originated from 1 (0.18%) of 555 samples of ground veal. Recovery rates for STEC were not associated with state, season, packaging type, or store type (P > 0.05) but were associated with brand and fat content (P < 0.05). Pulsed-field subtyping of the 270 viable and confirmed STEC isolates from the 64 total samples testing positive revealed 78 pulsotypes (50 to 80% similarity) belonging to 39 pulsogroups, with ≥90% similarity among pulsotypes within pulsogroups. Multiple isolates from 43 (67.7%) of 64 samples testing positive had an indistinguishable pulsotype. STEC serotypes O26 and O103 were the most prevalent serogroups in beef and veal, respectively. These findings support related findings from regulatory sampling studies over the past decade and confirm that recovery rates for the regulated STEC serogroups are higher for raw veal than for raw beef samples, as was observed in the present study of meat purchased at food retailers in the mid-Atlantic region of the United States.

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Characterization of Non-O157 Shiga Toxin-Producing Escherichia coli Cultured from Cattle Farms in Xinjiang Uygur Autonomous Region, China, During 2016-2017

Most outbreaks of Shiga toxin-producing Escherichia coli (STEC) are attributed to consumption of contaminated foodstuffs including beef and dairy products. In this study, we evaluated the prevalence of non-O157 STEC cultured from beef and dairy cattle and collected in Xinjiang Uygur Autonomous Region in China. Results identified 67 non-O157 STEC recovered from the 793 samples including beef cattle (10.28%, 43/418) and dairy cattle (6.40%, 24/375). A total of 67 non-O157 STEC was sequenced allowing for in silico analyses of their serotypes, virulence genes, and identification of the corresponding multilocus sequence types (STs). Twenty-one O serogroups and nine H serotypes were identified and the dominant serotype identified was O22:H8. One stx1 subtype (stx1a) and four stx2 subtypes (2a, 2b, 2c, and 2d) were found in the 67 non-O157 STEC isolates. The results revealed that stx1a+stx2a-positive STEC isolates were predominant (32.83%, 22/67), followed by stx1a+stx2d (29.85%, 20/67) and stx2a alone (17.91%, 12/67). Non-O157 STEC isolates carried virulence genes ehxA (98.51%), subA (53.73%), and cdtB (17.91%). Of the four adherence-associated genes tested, eaeA was absent, whereas lpfA and iha were present in 67 and 55 non-O157 STEC isolates, respectively. The STEC isolates were divided into 48 pulsed-field gel electrophoresis patterns and 10 STs, and ST446 (O22:H8) was the dominant clone (22.38%). Our results revealed that there was a high genetic diversity among non-O157 STEC isolated from beef and dairy cattle, some of which have potential to cause human diseases.

Comparison between the Real-Time PCR and Crystal Diagnostic Xpress Immunoassay Methods for Detecting Salmonella and Shiga Toxin-Producing Escherichia coli in the Air of Beef Slaughter Establishments

ABSTRACT

The aim of this study was to compare the effectiveness of a quantitative real-time PCR (qPCR) molecular method and the Crystal Diagnostic Xpress (CDx) immunoassay for detecting Salmonella and Shiga toxin-producing Escherichia coli (STEC) in air samples collected from abattoirs in Texas. The 70 air samples were collected from two small and two large meat processing plants in the spring and summer with a wetted wall cyclone air sampler. The samples were divided equally into two parts: one part was used for the qPCR assay, and the other part was enriched for 18 and 36 h and evaluated with the CDx immunoassay. All samples for which positive results were obtained were confirmed by plating and by biochemical and serological tests as recommended by AOAC International to verify results of rapid methods. With the qPCR and CDx assays and 36 h of enrichment, 37.5 and 57.1% of the samples, respectively, were positive for Salmonella (P < 0.05) and 65.0 and 60.7%, respectively, were positive for STEC (P > 0.05). Air samples required longer enrichment for the CDx immunoassay than recommended by the manufacturer for food samples. Recovery of Salmonella and STEC increased 16 and 47%, respectively, when enrichment was extended from 18 to 36 h. The prevalence of Salmonella and STEC obtained with both methods was affected by the size of the processing plant and the processing stage. Detection rates for samples from larger plants were higher for both pathogens. Significantly higher prevalence was obtained for samples from the stunning and dehiding areas than for those from the fabrication rooms and chillers. Salmonella detection was higher with the CDx assay than with the qPCR assay, but no differences were found for the detection of STEC by the qPCR and CDx assays. These results highlight the importance of method adjustments when testing matrices other than foods. More research is needed to understand the dynamics of pathogen dispersal in aerosols and how this affects the effectiveness of current rapid detection methods.

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Shiga Toxin-Producing Escherichia coli in Feces of Finisher Pigs: Isolation, Identification, and Public Health Implications of Major and Minor Serogroups†

ABSTRACT

Shiga toxin-producing Escherichia coli (STEC) are major foodborne human pathogens that cause mild to hemorrhagic colitis, which could lead to complications of hemolytic uremic syndrome. Seven serogroups, O26, O45, O103, O111, O121, O145, and O157, account for the majority of the STEC illnesses in the United States. Shiga toxins 1 and 2, encoded by stx1 and stx2, respectively, and intimin, encoded by eae gene, are major virulence factors. Cattle are a major reservoir of STEC, but swine also harbor them in the hindgut and shed STEC in the feces. Our objectives were to use a culture method to isolate and identify major and minor serogroups of STEC in finisher pig feces. Shiga toxin genes were subtyped to assess public health implications of STEC. Fecal samples (n = 598) from finisher pigs, collected from 10 pig flows, were enriched in E. coli broth and tested for stx1, stx2, and eae by a multiplex PCR (mPCR) assay. Samples positive for stx1 or stx2 gene were subjected to culture methods, with or without immunomagnetic separation and plating on selective or nonselective media, for isolation and identification of stx-positive isolates. The culture method yielded a total of 178 isolates belonging to 23 serogroups. The three predominant serogroups were O8, O86, and O121. The 178 STEC strains included 26 strains with stx1a and 152 strains with stx2e subtypes. Strains with stx1a, particularly in association with eae (O26 and O103), have the potential to cause severe human infections. All stx2-positive isolates carried the subtype stx2e, a subtype that causes edema disease in swine, but is rarely involved in human infections. Several strains were also positive for genes that encode for enterotoxins, which are involved in neonatal and postweaning diarrhea in swine. In conclusion, our study showed that healthy finisher pigs harbored and shed several serogroups of E. coli carrying virulence genes involved in neonatal diarrhea, postweaning diarrhea, and edema disease, but prevalence of STEC of public health importance was low.

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Thermal Resistance of Single Strains of Shiga Toxin-Producing Escherichia coli O121:H19 and O157:H7 Based on Culture Preparation Method and Osmolyte-Reduced Water Activity

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Bacterial exposure to stress, such as reduced water activity (aw), can increase thermal resistance. Pathogen thermal resistance studies on low-aw foods use a variety of methods to inoculate food, as well as strategies to reduce aw, which can influence observations. This study investigated effects of culture preparation method and osmolyte-induced aw on thermal resistance of two Shiga toxin-producing Escherichia coli (STEC) strains (O121:H19 and O157:H7) challenged with isothermal conditions, determining D- and z-values for each isolate (56, 59, and 62°C). Tryptic soy broth (TSB) and agar (lawn cultures) were compared. D-values of broth cultures were significantly and consistently larger than those of lawn cultures, and O121 was significantly more resistant than O157, but only at 56°C (P < 0.05). To compare potential effects of aw on STEC thermal resistance, cells were suspended in osmolyte solutions with varying aw: high (TSB, aw 0.99), intermediate (61% glycerol or 26% NaCl, aw 0.75), and low (82% glycerol, aw 0.5). In most instances, STEC strains in high-aw broth exhibited greater heat resistance compared to reduced-aw solutions, with the exception of the glycerol intermediate-aw solution (aw 0.75). Magnitudes varied with strain and temperature. The z-values of lawn cultures were significantly lower than those of broth cultures (P < 0.05), but there were few differences between high-aw and reduced-aw samples. There were no significant differences of z-values based on strain type. These results highlight that thermal resistance can be affected by culture preparation and that osmolyte-induced changes to aw influence thermal inactivation of STEC by varying magnitudes. These results emphasize the challenges of extrapolating results from laboratory inactivation kinetic experiments to determine the inactivation of low-aw foods, especially those considered dry in nature.

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Growth and Survival of Foodborne Pathogens during Soaking and Drying of Almond (Prunus dulcis) Kernels

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The practice of soaking almonds prior to consumption is popular both commercially and at home. The food safety implications of soaking almonds was investigated through analysis of blogs and videos (n = 85 recipes) to identify both the reasons for soaking almonds and the common practices employed. Among the recipes analyzed, the most common reasons for soaking almonds (94.1%) were perceived benefits such as improved digestion and nutrient uptake. Most recipes (34.1%) suggested soaking at "room temperature" for times that ranged from 4 to 24 h or, more commonly, "overnight" (51.8%). Postsoaking drying instructions were provided in 40 recipes (47.1%). Among those providing a drying temperature (31.8%), 85% specified 66°C and lower. To evaluate the growth of foodborne pathogens during almond soaking, separate cocktails of Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella enterica were inoculated onto raw almonds or into the soak water (almonds-to-water ratios of 1:1 and 1:3 [w/v]). Populations were monitored during soaking at 15, 18, and 23°C for up to 24 h, and during postsoak drying at 66°C for 14 h (for Salmonella only). At 15°C and a 1:1 almond:water ratio, no significant population increase (P > 0.05) was observed between 0 and 24 h for any of the pathogens. At 18°C, increases of 0.63, 1.70, and 0.88 log CFU per sample were observed over 24 h for populations of E. coli O157:H7, L. monocytogenes, and Salmonella, respectively. Populations of E. coli O157:H7, L. monocytogenes, and Salmonella increased by 3.48, 3.22, and 3.94 log CFU per sample, respectively, after 24 h at 23°C. When soaked almonds were dried for 14 h at 66°C, moisture and water activity decreased from 40 to ∼6% and 0.99 to 0.60, respectively, but no significant reduction in Salmonella populations was observed. Recommendations for using shorter times (<8 h) and cooler temperatures (≤15°C) should reduce the potential for foodborne pathogens, if present, to grow during soaking of almonds.

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Lessons Learned from a Decade of Investigations of Shiga Toxin-Producing Escherichia coli Outbreaks Linked to Leafy Greens, United States and Canada

Shiga toxin-producing Escherichia coli (STEC) cause substantial and costly illnesses. Leafy greens are the second most common source of foodborne STEC O157 outbreaks. We examined STEC outbreaks linked to leafy greens during 2009-2018 in the United States and Canada. We identified 40 outbreaks, 1,212 illnesses, 77 cases of hemolytic uremic syndrome, and 8 deaths. More outbreaks were linked to romaine lettuce (54%) than to any other type of leafy green. More outbreaks occurred in the fall (45%) and spring (28%) than in other seasons. Barriers in epidemiologic and traceback investigations complicated identification of the ultimate outbreak source. Research on the seasonality of leafy green outbreaks and vulnerability to STEC contamination and bacterial survival dynamics by leafy green type are warranted. Improvements in traceability of leafy greens are also needed. Federal and state health partners, researchers, the leafy green industry, and retailers can work together on interventions to reduce STEC contamination.

Analysis of Bacterial Diversity in Relation to the Presence of the Top 7 Shiga Toxin-Producing Escherichia coli throughout Australian Beef Abattoirs

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There is increasing evidence that diversity changes in bacterial communities of beef cattle correlate to the presence of Shiga toxin-producing Escherichia coli (STEC). However, studies that found an association between STEC and bacterial diversity have been focused on preslaughter stages in the beef supply chain. This study was designed to test a hypothesis that there are no differences in bacterial diversity between samples with and those without the presence of the top 7 STEC (O26, O45, O103, O111, O121, O145, and O157) throughout processing in an integrated (abattoir A) and a fragmented (abattoir B) Australian beef abattoir. Slaughter and boning room surface samples from each abattoir were analyzed using 16S rRNA amplicon sequencing and tested for the top 7 STEC following the Food Safety and Inspection Service protocol. Potential positives through slaughter were similar between the abattoirs (64 to 81%). However, abattoir B had substantially reduced potential positives in the boning room compared with abattoir A (abattoir A: 23 and 48%; abattoir B: 2 and 7%). Alpha diversity between the sample groups was not significantly different (P > 0.05) regardless of different STEC markers. Nonmetric multidimensional scaling of slaughter samples showed that the bacterial composition in fecal and hide samples shared the least similarity with the communities in carcass and environmental samples. Surface samples from slaughter (carcass and environmental) and boning (carcass, beef trim, and environmental) all appeared randomly plotted on the scale. This indicated that the STEC presence also did not have a significant effect (P > 0.05) on beta diversity. Although presence of STEC appeared to correlate with changes in diversity of fecal and hide bacterial communities in previous studies, it did not appear to have the same effect on other samples throughout processing.

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Evaluation of UVC Radiation and a UVC-Ozone Combination as Fresh Beef Interventions against Shiga Toxin-Producing Escherichia coli, Salmonella, and Listeria monocytogenes and Their Effects on Beef Quality

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This research study was conducted to evaluate treatments with UVC light and a combination of UVC and ozone that have recently received attention from the beef processing industry as antimicrobial interventions that leave no chemical residues on products. The effectiveness of UVC and UVC plus gaseous ozone treatments was evaluated for inactivation of pathogenic bacteria on fresh beef and for any impact on fresh beef quality. Fresh beef tissues were inoculated with cocktails of Shiga toxin-producing Escherichia coli (STEC) strains (serotypes O26, O45, O103, O111, O121, O145, and O157:H7), Salmonella, and Listeria monocytogenes. Inoculated fresh beef tissues were subjected to UVC or UVC-ozone treatments at 106 to 590 mJ/cm2. UVC treatment alone or in combination with ozone reduced populations of STEC, Salmonella, L. monocytogenes, and aerobic bacteria from 0.86 to 1.49, 0.76 to 1.33, 0.5 to 1.14, and 0.64 to 1.23 log CFU, respectively. Gaseous ozone alone reduced populations of E. coli O157:H7, Salmonella, and L. monocytogenes by 0.65, 0.70, and 0.33 log CFU, respectively. Decimal reduction times (D-values) for STEC serotypes, Salmonella, and L. monocytogenes on surfaces of fresh beef indicated that the UVC-ozone treatment was more effective (P ≤ 0.05) than UVC light alone for reducing pathogens on the surface of fresh beef. Exposure to UVC or UVC plus gaseous ozone did not have a deleterious effect on fresh meat color and did not accelerate the formation of oxidative rancidity. These findings suggest that UVC and UVC in combination with gaseous ozone can be useful for enhancing the microbial safety of fresh beef without impairing fresh beef quality.

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Performance of Chromogenic Agar Media for Isolation of Shiga Toxin-Producing Escherichia coli from Ground Beef

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The performance of three chromogenic agar media for detection of the "top seven" Shiga toxin-producing Escherichia coli (STEC) in beef was compared. Samples of retail ground beef were inoculated with STEC O26, O45, O103, O111, O121, O145, or O157 at geometric mean (±standard error of the mean) levels of 0, 48 (±1), 420 (±1), 4,100 (±1), or 45,000 (±1) CFU/10 g and enriched 1:10 (90 mL) in EC broth (40°C for 6 h). Following enrichment, aliquots of broth culture were treated by immunomagnetic separation with one of three pools of beads against the seven STEC serogroups: pool I, O26, O45, and O121; pool II, O103, O111, and O145; and pool III, O157. After immunomagnetic separation, 50 μL of washed bead suspensions in buffered peptone water were spiral plated onto modified Rainbow Agar O157 (mRBA), CHROMagar STEC (CS), or modified Possé differential medium (mPossé2) and incubated at 37°C for 18 h. Up to six isolated colonies were picked from each spiral plate based on expected colony phenotypes for STEC on the respective media, and isolate identity was confirmed with an 11-plex PCR assay targeting the O serogroups and virulence genes. Overall, mRBA had the highest sensitivity (99.2%), correctly detecting a significantly higher proportion of STEC serogroups than either CS (79.4%; P < 0.05) or mPossé2 (91.7%; P < 0.05). mRBA also had the highest negative predictive value (90.0%), correctly identifying a significantly higher proportion of true-negative samples compared with CS (25.7%; P < 0.05) and mPossé2 (46.2%; P < 0.05). However, mRBA also had the lowest analytical specificity of 83.2% (P < 0.05), yielding the lowest proportion of colonies tested that were STEC positive (3,548 of 4,263) compared with 97.7% (3,607 of 3,693) for mPossé2 and 98.0% (2,875 of 2,935) for CS. Reduced specificity results in more work and higher expense due to the increased number of colonies that must be tested. Further improvements in agar culture media for non-O157 STEC isolation are needed.

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Inactivation of Shiga Toxin-Producing Escherichia coli and Listeria monocytogenes within Plant versus Beef Burgers in Response to High Pressure Processing

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We evaluated high pressure processing to lower levels of Shiga toxin-producing Escherichia coli (STEC) and Listeria monocytogenes inoculated into samples of plant or beef burgers. Multistrain cocktails of STEC and L. monocytogenes were separately inoculated (∼7.0 log CFU/g) into plant burgers or ground beef. Refrigerated (i.e., 4°C) or frozen (i.e., -20°C) samples (25 g each) were subsequently exposed to 350 MPa for up to 9 or 18 min or 600 MPa for up to 4.5 or 12 min. When refrigerated plant or beef burger samples were treated at 350 MPa for up to 9 min, levels of STEC were reduced by ca. 0.7 to 1.3 log CFU/g. However, when refrigerated plant or beef burger samples were treated at 350 MPa for up to 9 min, levels of L. monocytogenes remained relatively unchanged (ca. ≤0.3-log CFU/g decrease) in plant burger samples but were reduced by ca. 0.3 to 2.0 log CFU/g in ground beef. When refrigerated plant or beef burger samples were treated at 600 MPa for up to 4.5 min, levels of STEC and L. monocytogenes were reduced by ca. 0.7 to 4.1 and ca. 0.3 to 5.6 log CFU/g, respectively. Similarly, when frozen plant and beef burger samples were treated at 350 MPa up to 18 min, reductions of ca. 1.7 to 3.6 and ca. 0.6 to 3.6 log CFU/g in STEC and L. monocytogenes numbers, respectively, were observed. Exposure of frozen plant or beef burger samples to 600 MPa for up to 12 min resulted in reductions of ca. 2.4 to 4.4 and ca. 1.8 to 3.4 log CFU/g in levels of STEC and L. monocytogenes, respectively. Via empirical observation, pressurization did not adversely affect the color of plant burger samples, whereas appreciable changes in color were observed in pressurized ground beef. These data confirm that time and pressure levels already validated for control of STEC and L. monocytogenes in ground beef will likely be equally effective toward these same pathogens in plant burgers without causing untoward effects on product color.

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The Efficacy and Safety of Fecal Microbiota Transplant for Recurrent Clostridium difficile Infection: Current Understanding and Gap Analysis

The leading risk factor for Clostridioides (Clostridium) difficile infection (CDI) is broad-spectrum antibiotics, which lead to low microbial diversity, or dysbiosis. Current therapeutic strategies for CDI are insufficient, as they do not address the key role of the microbiome in preventing C. difficile spore germination into toxin-producing vegetative bacteria, which leads to symptomatic disease. Fecal microbiota transplant (FMT) appears to reduce the risk of recurrent CDI through microbiome restoration. However, a wide range of efficacy rates have been reported, and few placebo-controlled trials have been conducted, limiting our understanding of FMT efficacy and safety. We discuss the current knowledge gaps driven by questions around the quality and consistency of clinical trial results, patient selection, diagnostic methodologies, use of suppressive antibiotic therapy, and methods for adverse event reporting. We provide specific recommendations for future trial designs of FMT to provide improved quality of the clinical evidence to better inform treatment guidelines.

Associations Between Season, Processing Plant, and Hide Cleanliness Scores with Prevalence and Concentration of Major Shiga Toxin-Producing Escherichia coli on Beef Cattle Hides

The objectives of this study were (1) to estimate the prevalence and concentration of the seven major Shiga toxin-producing Escherichia coli (STEC) serogroups (O26, O45, O103, O111, O121, O145, and O157), collectively called STEC-7, on cattle hides collected in different seasons and beef processing plants; and (2) to determine associations of season, plant, and hide cleanliness scores with the prevalence and concentration of STEC-7. A total of 720 hide surface samples (240/season) were collected over three seasons (summer and fall 2015 and spring 2016) from beef cattle carcasses in four commercial processing plants in the United States. Samples were subjected to selective culture and spiral plating methods. Overall model-adjusted mean prevalence (95% confidence interval) was 0.3% (0.03-2.3%) for STEC O26; 0.05% (<0.01-8.5%) for STEC O45; 0.2% (0.02-1.9%) for STEC O103; 0.05% (<0.01-8.5%) for STEC O145; and 3.1% (0.6-15.2%) for STEC O157. Four percent of hide samples were enumerable for STEC O157; mean concentration (standard deviation) = 2.1 (0.7) log₁₀ colony-forming units (CFUs)/100 cm². No samples were enumerable for non-O157 STEC. Hide-on prevalence of STEC O157 and STEC non-O157 (specifically of STEC O103) was higher in summer and spring, respectively. Across seasons and plants, the most common STEC non-O157 serogroups in this study (O26 and O103) were associated with a higher prevalence of STEC O157. Season and plant played a role in prevalence and concentration of STEC in beef cattle hides, varying by serogroup. Tailoring mitigation strategies at the plant can be challenging and processors would benefit from supplementary preharvest interventions to reduce overall contamination pressure at the plant, especially in fall and spring months when hide-on prevalence of STEC non-O157 is higher.

Phage Biocontrol Improves Food Safety by Significantly Reducing the Level and Prevalence of Escherichia coli O157:H7 in Various Foods

ABSTRACT

Management of Shiga toxin-producing Escherichia coli (STEC), including E. coli O157:H7, in food products is a major challenge for the food industry. Several interventions, such as irradiation, chemical disinfection, and pasteurization, have had variable success controlling STEC contamination. However, these interventions also indiscriminately kill beneficial bacteria in foods, may impact organoleptic properties of foods, and are not always environmentally friendly. Biocontrol using bacteriophage-based products to reduce or eliminate specific foodborne pathogens in food products has been gaining attention due to the specificity, safety, and environmentally friendly properties of lytic bacteriophages. We developed EcoShield PX, a cocktail of lytic bacteriophages, that specifically targets STEC. This study was conducted to examine the efficacy of this bacteriophage cocktail for reducing the levels of E. coli O157:H7 in eight food products: beef chuck roast, ground beef, chicken breast, cooked chicken, salmon, cheese, cantaloupe, and romaine lettuce. The food products were challenged with E. coli O157:H7 at ca. 3.0 log CFU/g and treated with the bacteriophage preparation at ca. 1 × 106, 5 × 106, or 1 × 107 PFU/g. Application of 5 × 106 and 1 × 107 PFU/g resulted in significant reductions (P < 0.05) in E. coli O157:H7 levels of up to 97% in all foods. When bacteriophages (ca. 1 × 106 PFU/g) were used to treat lower levels of E. coli O157:H7 (ca. 1 to 10 CFU/10 g) on beef chuck roast samples, mimicking the levels of STEC found under real-life conditions in food processing plants, the prevalence of STEC in the samples was significantly reduced (P < 0.05) by ≥80%. Our results suggest that this STEC-targeting bacteriophage preparation can result in significant reduction of both the levels and prevalence of STEC in various foods and, therefore, may help improve the safety and reduce the risk of recalls of foods at high risk for STEC contamination.

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Salmonella and Shiga Toxin-Producing Escherichia coli in Products Sampled in the Food Safety and Inspection Service Raw Pork Baseline Study

The Food Safety and Inspection Service (FSIS) conducts microbiological baseline studies to determine national prevalence of select foodborne pathogens in federally inspected meat and poultry products and to obtain data for risk assessments. The FSIS conducted a baseline study from 1 June 2017 through 31 May 2018 to characterize and determine the prevalence of Salmonella and assess the occurrence of Shiga toxin-producing Escherichia coli (STEC) in a variety of raw pork products. In total, 4,014 samples from slaughter and processing establishments were analyzed for Salmonella; a subset of these samples (1,395) from slaughter establishments were also analyzed for STEC. Analyses determined that the national prevalence of Salmonella in raw pork products was highest in comminuted products (28.9%), followed by intact cuts (5.3%) and nonintact cuts (3.9%). Less than 1% of samples analyzed were positive for the top seven STEC. Our findings indicate there is a need for additional pathogen reduction strategies for raw pork products.

Viability of Shiga Toxin-Producing Escherichia coli, Salmonella, and Listeria monocytogenes within Plant versus Beef Burgers during Cold Storage and following Pan Frying

ABSTRACT

The viability of Shiga toxin-producing Escherichia coli (STEC), Salmonella, and Listeria monocytogenes within plant- and beef-based burgers was monitored during storage and cooking. When inoculated (ca. 3.5 log CFU/g) into 15-g portions of plant- or beef-based burgers, levels of STEC and Salmonella decreased slightly (≤0.5-log decrease) in both types of burgers when stored at 4°C, but increased ca. 2.4 and 0.8 log CFU/g, respectively, in plant-based burgers but not beef-based burgers (≤1.2-log decrease), after 21 days at 10°C. For L. monocytogenes, levels increased by ca. 1.3 and 2.6 log CFU/g in plant burgers after 21 days at 4 and 10°C, respectively, whereas pathogen levels decreased slightly (≤0.9-log decrease) in beef burgers during storage at 4 and 10°C. Regarding cooking, burgers (ca. 114 g each) were inoculated with ca. 7.0 log CFU/g STEC, Salmonella, or L. monocytogenes and cooked in a sauté pan. Cooking plant- or beef-based burgers to 62.8°C (145°F), 68.3°C (155°F), or 73.9°C (165°F) delivered reductions ranging from ca. 4.7 to 6.8 log CFU/g for STEC, ca. 4.4 to 7.0 log CFU/g for L. monocytogenes, and ca. 3.5 to 6.7 log CFU/g for Salmonella. In summary, the observation that levels of all three pathogens increased by ca. 1.0 to ca. 2.5 log CFU/g in plant-based burgers when stored at an abusive temperature (10°C) highlights the importance of proper storage (4°C) to lessen risk. However, because all three pathogens responded similarly to heat in plant-based as in beef-based burgers, well-established cooking parameters required to eliminate STEC, Salmonella, or L. monocytogenes from ground beef should be as effective for controlling cells of these same pathogens in a burger made with plant-sourced protein.

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Evaluation of Bactericidal Effects of Phenyllactic Acid on Escherichia coli O157:H7 and Salmonella Typhimurium on Beef Meat

Bactericidal effects of various concentrations of phenyllactic acid on Shiga toxin-producing Escherichia coli (STEC), including E. coli O157:H7, O26:H11, O103:H2, and O121:H19, and on Salmonella Typhimurium DT104 in pure culture and microplates assays were studied. Beef cuts were surface sprayed with phenyllactic acid or lactic acid for inactivation of E. coli O157:H7 and Salmonella Typhimurium. The 1.5% phenyllactic acid inactivated all inoculated E. coli O157:H7, O26:H11, O103:H2, and O121:H19 and Salmonella Typhimurium DT104 (>6-log reduction) within 1 min of contact at 21°C, whereas 1.5% lactic acid did not result in microbial reduction. Microplate assays (for STEC and Salmonella Typhimurium DT104 at 10 to 100 CFU per well) indicated that concentrations of 0.25% phenyllactic acid or 0.25% lactic acid inhibited the growth of STEC and Salmonella Typhimurium DT104 incubated at 37°C for 24 h. Treatment of beef with 1.5% lactic acid or 1.5% phenyllactic acid reduced E. coli O157:H7 by 0.22 and 0.38 log CFU/cm², respectively, within 5 min and reduced Salmonella Typhimurium DT104 by 0.12 and 0.86 log CFU/cm², respectively. When meat treated with 1.5% phenyllactic acid was frozen at -20°C, inactivation of E. coli O157 and Salmonella Typhimurium DT104 was enhanced by 1.06 and 1.46 log CFU/cm², respectively. Thus, treatment of beef with 1.5% phenyllactic acid significantly reduced the population of E. coli O157:H7 and Salmonella.

Outbreaks of Shiga Toxin-Producing Escherichia coli Linked to Sprouted Seeds, Salad, and Leafy Greens: A Systematic Review

Shiga toxin-producing Escherichia coli (STEC) outbreaks involving ready-to-eat salad products have been described in the scientific literature since 1995. These products typically do not undergo a definitive control step such as cooking to eliminate pathogens. To reduce the number of STEC infections from salad products, efforts will need to focus on preventing and reducing contamination throughout the food chain. We performed a systematic review of STEC outbreaks involving sprouted seeds, salad, or leafy green products to determine whether there were recurrent features, such as availability of microbiological evidence or identification of the contamination event, which may inform future investigations and prevention and control strategies. Thirty-five STEC outbreaks linked to contaminated leafy greens were identified for inclusion. The outbreaks occurred from 1995 to 2018 and ranged from 8 to more than 8,500 cases. Detection of STEC in the food product was rare (4 of 35 outbreaks). For the remaining outbreaks, the determination of leafy greens as the source of the outbreak mainly relied on analytical epidemiology (20 of 35) or descriptive evidence (11 of 35). The traceback investigation in 21 of 32 outbreaks was not able to identify possible routes leading to where the STEC bacteria came from or how the leaves were contaminated. Investigations in eight outbreaks found poor practice during processing that may have contributed to the outbreak, such as insufficient postharvest disinfection of the product. Six outbreak investigations were able to identify the outbreak strain in animal feces near the growing fields; two of these were also able to find it in irrigation water on the farms, providing a likely route of contamination. These results highlight the limitations of relying on microbiological confirmation as a basis to initiate investigations of upstream production to understand the source of contamination. This review also demonstrates the importance of, and difficulties associated with, food-chain traceback studies to inform control measures and future prevention.

Survey of Intact and Nonintact Raw Pork Collected at Retail Stores in the Mid-Atlantic Region of the United States for the Seven Regulated Serogroups of Shiga Toxin-Producing Escherichia coli

A total of 514 raw pork samples (395 ground or nonintact and 119 intact samples) were purchased at retail stores in Pennsylvania, Delaware, and New Jersey between July and December 2017. All raw pork samples were screened for serogroup O26, O45, O103, O111, O121, O145, or O157:H7 cells of Shiga toxin-producing Escherichia coli (STEC-7) using standard microbiological and molecular methods. In short, 21 (5.3%) of the 395 ground or nonintact pork samples and 3 (3.4%) of the 119 intact pork samples tested positive via the BAX system real-time PCR assay for the stx and eae virulence genes and for the somatic O antigens for at least one of the STEC-7 serogroups. However, none of these 24 presumptive-positive pork samples subsequently yielded a viable isolate of STEC displaying a STEC-7 serogroup-specific surface antigen in combination with the stx and eae genes. These data suggest that cells of STEC serogroups O26, O45, O103, O111, O121, O145, or O157:H7 are not common in retail raw pork samples in the mid-Atlantic region of the United States.

Highly Pathogenic Clone of Shiga Toxin-Producing Escherichia coli O157:H7, England and Wales

We used whole-genome sequencing to investigate the evolutionary context of an emerging highly pathogenic strain of Shiga toxin–producing Escherichia coli (STEC) O157:H7 in England and Wales. A timed phylogeny of sublineage IIb revealed that the emerging clone evolved from a STEC O157:H7 stx-negative ancestor ≈10 years ago after acquisition of a bacteriophage encoding Shiga toxin (stx) 2a, which in turn had evolved from a stx2c progenitor ≈20 years ago. Infection with the stx2a clone was a significant risk factor for bloody diarrhea (OR 4.61, 95% CI 2.24–9.48; p<0.001), compared with infection with other strains within sublineage IIb. Clinical symptoms of cases infected with sublineage IIb stx2c and stx-negative clones were comparable, despite the loss of stx2c. Our analysis highlighted the highly dynamic nature of STEC O157:H7 Stx-encoding bacteriophages and revealed the evolutionary history of a highly pathogenic clone emerging within sublineage IIb, a sublineage not previously associated with severe clinical symptoms.

Presence of Multidrug-Resistant Shiga Toxin-Producing Escherichia coli, Enteropathogenic Escherichia coli, and Enterotoxigenic Escherichia coli on Fresh Cheeses from Local Retail Markets in Mexico

Cheesemaking is one of the most important industries in Mexico. Among all the Mexican cheeses, fresh cheeses are the most popular and most consumed cheese in Mexico and Latin America. However, in Mexico fresh cheese is frequently made with unpasteurized milk and sold in public markets. This may increase the risk for contamination of dairy products with pathogenic bacteria. The presence of multidrug-resistant pathogenic bacteria in food is an important public health concern. Diarrheagenic Escherichia coli pathotypes (DEPs) are foodborne bacteria. This study investigated the presence of indicator bacteria and multidrug-resistant DEPs in fresh cheeses. A total of 120 fresh cheese samples were collected from public markets in the city of Pachuca, Mexico. The samples were analyzed for presence of fecal coliforms (FC), E. coli, and antibiotic resistant DEPs. FC and E. coli were analyzed using the most-probable-number technique. DEPs were identified using two multiplex PCR methods. Susceptibility to 16 antibiotics was tested for the isolated DEPs strains by the standard assay. The frequency of FC, E. coli, and DEPs in the cheese samples was 50, 40, and 19%, respectively. The identified DEPs included Shiga toxin-producing E. coli (STEC; 8%), enteropathogenic E. coli (EPEC; 6%), and enterotoxigenic E. coli (ETEC; 5%). All isolated strains exhibited resistance to at least five antibiotics. One, one, two, and three STEC strains were resistant to 14, 12, 11, and 10 antibiotics, respectively. One strain of EPEC was resistant to 11 antibiotics, three EPEC strains to 9, and one strain to 7. One, one, and two strains of ETEC were resistant to 10, 8, and 7 antibiotics, respectively. The results of the present study indicate that fresh cheeses made with unpasteurized milk could be a risk for consumers, both for native people and visitors to Mexico.

Prevalence of Salmonella, Campylobacter, and Shiga Toxin-Producing Escherichia coli on the Surfaces of Raw Poultry Packages

Contamination on the exterior surfaces of raw poultry packages can be transmitted to hands and food contact surfaces during shopping and handling. This study compared the level of microbial contamination and prevalence of foodborne pathogens on the surfaces of raw poultry packages as related to the types of products, types of packaging, and packaging conditions. Packages of whole chicken, cut-up chicken (breast and leg quarter), and ground turkey were purchased from retail stores. Aerobic plate counts (APCs) were significantly different ( P < 0.05) among types of products and packaging materials, with ground turkey packages and the heat-sealed, high-walled containers being the lowest. APCs were significantly lower ( P < 0.05) when the packages were intact and tight compared with intact and loose. Of the 105 packages, there were 10 (9.5%) with the presence of either Shiga toxin-producing Escherichia coli (STEC) or Campylobacter; of those packages, 6 (5.7%) were positive for STEC, 7 (6.7%) were positive for Campylobacter, and 3 (2.9%) were positive for both pathogens on the surfaces. Salmonella was not detected on the surfaces of all tested packages. Surfaces of whole chicken packages were significantly ( P < 0.001) more likely to have detectable levels of Campylobacter and STEC than those of cut-up chicken packages. Packages that were positive for Campylobacter and/or STEC had significantly ( P < 0.005) higher APCs than negative packages. The results suggested that STEC is another significant pathogen present on the surfaces of poultry packages in addition to Campylobacter. The presence of STEC on the external packaging of raw poultry raises a concern because consumers may not expect such pathogens on the surfaces of poultry packages.

Detection and Quantification of Seven Major Serogroups of Shiga Toxin-Producing Escherichia coli on Hides of Cull Dairy, Cull Beef, and Fed Beef Cattle at Slaughter†

Dehiding during beef cattle processing can introduce fecal contaminants, including Shiga toxin-producing Escherichia coli (STEC), from hides onto carcass surfaces, creating the potential for contaminated beef. Fecal shedding of major STEC serogroups (O26, O45, O103, O111, O121, O145, and O157; STEC-7) may differ among cattle populations, yet no study has been conducted to isolate STEC-7 on hides of multiple cattle types on the same production days at the same processing plant. Our objective was to estimate and compare prevalence and concentrations of STEC-7 on hides of cull dairy, cull beef, and fed beef cattle from the same date and processing plant. Overall, 1,500 cattle hides were sponge sampled from cull dairy ( n = 500), cull beef ( n = 500) and fed beef cattle ( n = 500) over 10 processing days. To determine prevalence, samples were subjected to an immunomagnetic separation culture method, and presumptive STEC isolates were tested by PCR for serogroup and major virulence genes. A spiral plate method was used to enumerate STEC-7 from hide samples. Data were analyzed with linear mixed models. All STEC-7 serogroups except O121 were detected and quantified on cattle hides in this study population. Slightly more fed beef hides (77 of 500; 15.4%) and cull beef hides (76 of 500; 15.2%) were positive for at least one STEC-7 strain compared with cull dairy hides (57 of 500; 11.4%), but cattle type was not significantly associated ( P = 0.19) with STEC-7 prevalence. Fed beef hides had a significantly higher prevalence ( P < 0.05) of STEC O103, O145, and O157 serogroups than did either of the other cattle types. The highest proportions of quantifiable samples were for STEC O145 (32 of 1,500 samples; 2.1%) and O157 (31 of 1,500 samples; 2.1%) serogroups, with the majority of concentrations at 3 to 5 and 2 to 4 log CFU/100 cm² of hide, respectively. Results indicate that hide contamination with some major STEC serogroups differs significantly among cattle types at harvest, even within the same day and location.

Interlaboratory Evaluation of the U.S. Food and Drug Administration Escherichia coli Identification Microarray for Profiling Shiga Toxin-Producing Escherichia coli

The U.S. Food and Drug Administration Escherichia coli Identification (FDA-ECID) microarray provides rapid molecular characterization of E. coli. The effectiveness of the FDA-ECID for characterizing Shiga toxin-producing E. coli (STEC) was evaluated by three federal laboratories and one reference laboratory with a panel of 54 reference E. coli strains from the External Quality Assurance program. Strains were tested by FDA-ECID for molecular serotyping (O and H antigens), Shiga toxin subtyping, and the presence of the ehxA and eae genes for enterohemolysin and intimin, respectively. The FDA-ECID O typing was 96% reproducible among the four laboratories and 94% accurate compared with the reference External Quality Assurance data. Discrepancies were due to the absence of O41 target loci on the array and to two pairs of O types with identical target sequences. H typing was 96% reproducible and 100% accurate, with discrepancies due to two strains from one laboratory that were identified as mixed by FDA-ECID. Shiga toxin (Stx) type 1 subtyping was 100% reproducible and accurate, and Stx2 subtyping was 100% reproducible but only 64% accurate. FDA-ECID identified most Stx2 subtypes but had difficulty distinguishing among stx_2a, stx_2c, and stx_2d genes because of close similarities of these sequences. FDA-ECID was 100% effective for detecting ehxA and eae and accurately subtyped the eae alleles. This interlaboratory study revealed that FDA-ECID for STEC characterization was highly reproducible for molecular serotyping, stx and eae subtyping, and ehxA detection. However, the array was less useful for distinguishing among the highly homologous O antigen genes and the stx_2a, stx_2c, and stx_2d subtypes.