Characterization of Enterohemorrhagic Escherichia coli on Veal Hides and Carcasses

Sample Type and Processing Plant Differences in the Proportion of Enterohemorrhagic Escherichia coli O157 and Non-O157 Serogroups in Feces and on Hides of Cull Dairy Cattle at Slaughter

The study was conducted to determine the proportion and concentration of enterohemorrhagic Escherichia coli (EHEC) O157 and six non-O157 (O26, O45, O103, O111, O121, and O145) serogroups and identify seasonal and processing plant differences in feces and on hides of cull dairy cattle processed in commercial slaughterhouses in the United States. Approximately 60 rectal and 60 hide-on samples from matched carcasses were collected in each of three processing plants, in two periods; summer of 2017 and spring of 2018. Samples before enrichment were spiral plated to quantify EHEC, and postenriched samples underwent culture methods that included immuno-magnetic separation, plating on selective media, and PCR assays for identification and serogroup confirmation of putative isolates. An isolate was considered EHEC O157 positive if it harbored serogroup-specific (rfbE), Shiga toxin (stx1 and/or stx2), and intimin (eae) genes and EHEC non-O157 positive if at least one of the non-O157 serogroup-specific, stx1 and/or stx2, and eae genes was identified. Generalized linear mixed models were fitted to estimate overall proportion of positives for EHEC O157 and non-O157 EHEC serogroups, as well as seasonal and processing plant differences in fecal and hide-on proportion of positives. The fecal EHEC proportion at the sample level was 1.8% (95% CI = 0.0-92.2%) and 4.2% (95% CI = 0.0-100.0%) for EHEC O157 and EHEC non-O157, respectively. Hide sample level proportion of positives was 3.0% (95% CI = 0.0-99.9%) for EHEC O157 and 1.6% (95% CI = 0.0-100.0%) for EHEC non-O157. The proportion of EHEC O157 and non-O157 significantly differed by processing plant and sample type (hide vs. feces), but not by season. The association between proportion of EHEC serogroups in feces with the proportion on hides collected from matched cattle was 7.8% (95% CI = 0.6-53.3%) and 3.8% (95% CI = 0.3-30.8%) for EHEC O157 and non-O157, respectively. Taken together, our findings provide evidence of a low proportion of EHEC serogroups in the feces and on hides of cull dairy cattle and that their proportion varies across processing plants.

Proportions and Serogroups of Enterohemorrhagic Shiga Toxin-producing Escherichia coli in Feces of Fed and Cull Beef and Cull Dairy Cattle at Harvest

Cattle are considered a primary reservoir of Shiga toxin (stx)-producing Escherichia coli that cause enterohemorrhagic disease (EHEC), and contaminated beef products are one vehicle of transmission to humans. However, animals entering the beef harvest process originate from differing production systems: feedlots, dairies, and beef breeding herds. The objective of this study was to determine if fed cattle, cull dairy, and or cull beef cattle carry differing proportions and serogroups of EHEC at harvest. Feces were collected via rectoanal mucosal swabs (RAMSs) from 1,039 fed cattle, 1,058 cull dairy cattle, and 1,018 cull beef cattle at harvest plants in seven U.S. states (CA, GA, NE, PA, TX, WA, and WI). The proportion of the stx gene in feces of fed cattle (99.04%) was not significantly different (P > 0.05) than in the feces of cull dairy (92.06%) and cull beef (91.85%) cattle. When two additional factors predictive of EHEC (intimin and ecf1 genes) were considered, EHEC was significantly greater (P < 0.05) in fed cattle (77.29%) than in cull dairy (47.54%) and cull beef (38.51%) cattle. The presence of E. coli O157:H7 and five common non-O157 EHEC of serogroups O26, O103, O111, O121, and O145 was determined using molecular analysis for single nucleotide polymorphisms (SNPs) followed by culture isolation. SNP analysis identified 23.48%, 17.67%, and 10.81% and culture isolation confirmed 2.98%, 3.31%, and 3.00% of fed, cull dairy, and cull beef cattle feces to contain one of these EHEC, respectively. The most common serogroups confirmed by culture isolation were O157, O103, and O26. Potential EHEC of fourteen other serogroups were isolated as well, from 4.86%, 2.46%, and 2.01% of fed, cull dairy, and cull beef cattle feces, respectively; with the most common being serogroups O177, O74, O98, and O84. The identification of particular EHEC serogroups in different types of cattle at harvest may offer opportunities to improve food safety risk management.

Antibiotic Resistance and Disinfectant Resistance Among Escherichia coli Isolated During Red Meat Production

Escherichia coli commonly found in the gastrointestinal tracts of food animals include Shiga toxin-producing E. coli (STEC, stx+, eae-), Enterohemorrhagic E. coli (EHEC, stx+, eae+), Enteropathogenic E. coli (EPEC, stx-, eae+), and "nondiarrheagenic" E. coli (NDEC, stx-, eae-). EHEC, EPEC, and STEC are associated with foodborne disease outbreaks. During meat processing, disinfectants are employed to control various bacteria, including human pathogens. Concerns exist that E. coli resistant to antibiotics are less susceptible to disinfectants used during meat processing. Since EHEC, EPEC, and STEC with reduced susceptibility to disinfectants are potential public health risks, the goal of this study was to evaluate the association of antibiotic resistant (ABR) E. coli with increased tolerance to 4% lactic acid (LA) and 150 ppm quaternary ammonium compounds (QACs). A pool of 3,367 E. coli isolated from beef cattle, veal calves, swine, and sheep at various processing stages was screened to identify ABR E. coli. Resistance to ≥1 of the six antibiotics examined was identified in 27.9%, 36.1%, 54.5%, and 28.7% among the NDEC (n = 579), EHEC (n = 693), EPEC (n = 787), and STEC (n = 1308) isolates evaluated, respectively. Disinfectant tolerance did not differ (P > 0.05) between ABR and antibiotic susceptible EHEC isolates. Comparable frequencies (P > 0.05) of biofilm formation or congo red binding were observed between ABR and antibiotic susceptible strains of E. coli. Understanding the frequencies of ABR and disinfectant tolerance among E. coli present in food-animal is a critically important component of meat safety.

Evaluation of the Microbiological Status of Cattle Carcasses in Mongolia: Considering the Hygienic Practices of Slaughter Establishments

The meat industry has received great attention in Mongolia, having over 70 million livestock, and is important to the nation's economy. Systematic microbiological testing of carcasses has not been mandatorily regulated in all abattoir premises, and the efficacy of the introduction of the Good Hygiene Practice and Hazard Analysis Critical Control Points (HACCP) to some plants has not yet been tested microbiologically in Mongolia. Therefore, samples were collected from two establishments: plant A with an HACCP certificate from a third party and plant B without an HACCP certificate. The rates and levels of the total bacterial count (TBC) as overall hygiene indicators, the Enterobacteriaceae count (EBC) as fecal contamination indicators, and the Staphylococcus spp. count (SC) as personal hygiene indicators were determined on different parts of beef carcasses. The contamination rates in most parts were lower in plant A than in plant B (e.g., TBC in the rump and flank: 103-105 and 105-107, in plant A vs. 104-106 and 105-108 in plant B, respectively). Plant A also had a lower EBC and SC (p < 0.001). Furthermore, 2 out of 100 beef carcasses (2%) were positive for enterohemorrhagic Escherichia coli as a foodborne pathogen indicator in plant A.

Validation of Commonly Used Antimicrobial Interventions on Bob Veal Carcasses for Reducing Shiga Toxin-Producing Escherichia coli Surrogate Populations

ABSTRACT

Ruminants are natural reservoirs of Shiga toxin-producing Escherichia coli (STEC), and the STEC can be easily transferred to carcasses during the conversion of animals to meat. Three experiments were conducted to validate the efficacy of lactic acid (LA; 4%), peroxyacetic acid (PAA; 300 ppm), and hot water (HW; 80°C) for their individual or combined abilities to reduce STEC surrogates on bob veal carcasses pre- and postchill and through fabrication. In experiment 1, hot carcasses (n = 9) were inoculated with a five-strain cocktail (ca. 8 log CFU/mL) containing rifampin-resistant surrogate E. coli (BAA-1427, BAA-1428, BAA-1429, BAA-1430, and BAA-1431) and then treated with HW, LA, or PAA. Carcasses were then chilled (0 ± 1°C; 24 h) and split in half, and each side was treated with either LA or PAA. In experiment 2, hot carcasses (n = 3) were inoculated and chilled (24 h). After 24 h, the carcasses were split, and each side was treated with either LA or PAA. For experiment 3, carcasses (n = 3) were chilled for 24 h, split, inoculated, and treated with either LA or PAA. After chilling, carcasses from all three experiments were fabricated to subprimals and the cut surfaces were sampled to determine the translocation of bacteria. Experiment 1 showed that LA+LA was the most effective (P ≤ 0.05) treatment for reducing surrogate E. coli on veal. In experiments 2 and 3, LA and PAA were similar (P > 0.05) in their abilities to reduce E. coli on chilled veal carcasses. In experiments 1 and 2, all antimicrobial treatments resulted in undetectable levels (<0.2 log CFU/cm2) of surrogate E. coli on cut surfaces after fabrication, whereas low levels (1.7 and 1.0 log CFU/cm2 for LA and PAA, respectively) were observed in experiment 3. Of the antimicrobial interventions utilized, LA was more effective for reducing STEC surrogate populations on veal carcasses, pre- and/or postchill.

HIGHLIGHTS

Transmission Dynamics of Shiga Toxin-Producing Escherichia coli in New Zealand Cattle from Farm to Slaughter

Cattle are asymptomatic carriers of Shiga toxin-producing Escherichia coli (STEC) strains that can cause serious illness or death in humans. In New Zealand, contact with cattle feces and living near cattle populations are known risk factors for human STEC infection. Contamination of fresh meat with STEC strains also leads to the potential for rejection of consignments by importing countries. We used a combination of PCR/matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF) and whole-genome sequencing (WGS) to evaluate the presence and transmission of STEC on farms and in processing plants to better understand the potential pathways for human exposure and thus mitigate risk. Animal and environmental samples (n = 2,580) were collected from six farms and three meat processing plants in New Zealand during multiple sampling sessions in spring of 2015 and 2016. PCR/MALDI-TOF analysis revealed that 6.2% were positive for "Top 7" STEC. Top 7 STEC strains were identified in all sample sources (n = 17) tested. A marked increase in Top 7 STEC prevalence was observed between calf hides on farm (6.3% prevalence) and calf hides at processing plants (25.1% prevalence). Whole-genome sequencing was performed on Top 7 STEC bacterial isolates (n = 40). Analysis of STEC O26 (n = 25 isolates) revealed relatively low genetic diversity on individual farms, consistent with the presence of a resident strain disseminated within the farm environment. Public health efforts should focus on minimizing human contact with fecal material on farms and during handling, transport, and slaughter of calves. Meat processing plants should focus on minimizing cross-contamination between the hides of calves in a cohort during transport, lairage, and slaughter.IMPORTANCE Cattle are asymptomatic carriers of Shiga toxin-producing E. coli (STEC) strains, which can cause serious illness or death in humans. Contact with cattle feces and living near cattle are known risk factors for human STEC infection. This study evaluated STEC carriage in young calves and the farm environment with an in-depth evaluation of six farms and three meat processing plants over 2 years. An advanced molecular detection method and whole-genome sequencing were used to provide a detailed evaluation of the transmission of STEC both within and between farms. The study revealed widespread STEC contamination within the farm environment, but no evidence of recent spread between farms. Contamination of young dairy calf hides increased following transport and holding at meat processing plants. The elimination of STEC in farm environments may be very difficult given the multiple transmission routes; interventions should be targeted at decreasing fecal contamination of calf hides during transport, lairage, and processing.

Locus of Heat Resistance (LHR) in Meat-Borne Escherichia coli: Screening and Genetic Characterization

Microbial resistance to processing treatments poses a food safety concern, as treatment tolerant pathogens can emerge. Occasional foodborne outbreaks caused by pathogenic Escherichia coli have led to human and economic losses. Therefore, this study screened for the extreme heat resistance (XHR) phenotype as well as one known genetic marker, the locus of heat resistance (LHR), in 4,123 E. coli isolates from diverse meat animals at different processing stages. The prevalences of XHR and LHR among the meat-borne E. coli were found to be 10.3% and 11.4%, respectively, with 19% agreement between the two. Finished meat products showed the highest LHR prevalence (24.3%) compared to other processing stages (0 to 0.6%). None of the LHR⁺ E. coli in this study would be considered pathogens based on screening for virulence genes. Four high-quality genomes were generated by whole-genome sequencing of representative LHR⁺ isolates. Nine horizontally acquired LHRs were identified and characterized, four plasmid-borne and five chromosomal. Nine newly identified LHRs belong to ClpK1 LHR or ClpK2 LHR variants sharing 61 to 68% nucleotide sequence identity, while one LHR appears to be a hybrid. Our observations suggest positive correlation between the number of LHR regions present in isolates and the extent of heat resistance. The isolate exhibiting the highest degree of heat resistance possessed four LHRs belonging to three different variant groups. Maintenance of as many as four LHRs in a single genome emphasizes the benefits of the LHR in bacterial physiology and stress response.IMPORTANCE Currently, a "multiple-hurdle" approach based on a combination of different antimicrobial interventions, including heat, is being utilized during meat processing to control the burden of spoilage and pathogenic bacteria. Our recent study (M. Guragain, G. E. Smith, D. A. King, and J. M. Bosilevac, J Food Prot 83:1438-1443, 2020, https://doi.org/10.4315/JFP-20-103) suggests that U.S. beef cattle harbor Escherichia coli that possess the locus of heat resistance (LHR). LHR seemingly contributes to the global stress tolerance in bacteria and hence poses a food safety concern. Therefore, it is important to understand the distribution of the LHRs among meat-borne bacteria identified at different stages of different meat processing systems. Complete genome sequencing and comparative analysis of selected heat-resistant bacteria provide a clearer understanding of stress and heat resistance mechanisms. Further, sequencing data may offer a platform to gain further insights into the genetic background that provides optimal bacterial tolerance against heat and other processing treatments.

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.

HIGHLIGHTS

Detection, Prevalence, and Pathogenicity of Non-O157 Shiga Toxin-Producing Escherichia coli from Cattle Hides and Carcasses

Cattle are a major reservoir for Shiga toxin-producing Escherichia coli (STEC) and harbor these bacteria in the intestinal tract. The prevalence, concentration, and STEC serogroup isolated in cattle varies between individuals. Hide removal at slaughter serves as a major point of carcass contamination and ultimately beef products. Certain STEC serogroups, such as O26, O45, O103, O111, O121, O145, and O157, containing the intestinal adherence factor intimin, pose a large economic burden to food producers because of testing and recalls. Human infection with STEC can cause illnesses ranging from diarrhea to hemorrhagic colitis and hemolytic uremic syndrome, and is commonly acquired through ingestion of contaminated foods, often beef products. Previously, most studies focused on O157 STEC, but there is growing recognition of the importance of non-O157 STEC serogroups. This review summarizes detection methods, prevalence, and methods for prediction of pathogenicity of non-O157 STEC from cattle hides and carcasses. A synthesis of procedures is outlined for general non-O157 STEC and targeted detection of specific STEC serogroups. Standardization of sample collection and processing procedures would allow for more robust comparisons among studies. Presence of non-O157 STEC isolated from cattle hides and carcasses and specific factors, such as point of sample collection and season, are summarized. Also, factors that might influence STEC survival on these surfaces, such as the microbial population on hides and microbial adherence genes, are raised as topics for future investigation. Finally, this review gives an overview on studies that have used genetic and cell-based methods to identify specific phenotypes of non-O157 STEC strains isolated from cattle to assess their risk to human health.

Biofilms and Meat Safety: A Mini-Review

Biofilms are surface-attached microbial communities with distinct properties, which have a tremendous impact on public health and food safety. In the meat industry, biofilms remain a serious concern because many foodborne pathogens can form biofilms in areas at meat plants that are difficult to sanitize properly, and biofilm cells are more tolerant to sanitization than their planktonic counterparts. Furthermore, nearly all biofilms in commercial environments consist of multiple species of microorganisms, and the complex interactions within the community significantly influence the architecture, activity, and sanitizer tolerance of the biofilm society. This review focuses on the effect of microbial coexistence on mixed biofilm formation with foodborne pathogens of major concern in the fresh meat industry and their resultant sanitizer tolerance. The factors that would affect biofilm cell transfer from contact surfaces to meat products, one of the most common transmission routes that could lead to product contamination, are discussed as well. Available results from recent studies relevant to the meat industry, implying the potential role of bacterial persistence and biofilm formation in meat contamination, are reviewed in response to the pressing need to understand the mechanisms that cause "high event period" contamination at commercial meat processing plants. A better understanding of these events would help the industry to enhance strategies to prevent contamination and improve meat safety.

Molecular Epidemiology of Shiga Toxin-Producing Escherichia coli (STEC) on New Zealand Dairy Farms: Application of a Culture-Independent Assay and Whole-Genome Sequencing

New Zealand has a relatively high incidence of human cases of Shiga toxin-producing Escherichia coli (STEC), with 8.9 STEC cases per 100,000 people reported in 2016. Previous research showed living near cattle and contact with cattle feces as significant risk factors for STEC infections in humans in New Zealand, but infection was not linked to food-associated factors. During the 2014 spring calving season, a random, stratified, cross-sectional study of dairy farms (n = 102) in six regions across New Zealand assessed the prevalence of the "Top 7" STEC bacteria (serogroups O157, O26, O45, O103, O111, O121, and O145) in young calves (n = 1,508), using a culture-independent diagnostic test (PCR/MALDI-TOF). Twenty percent (306/1,508) of calves on 75% (76/102) of dairy farms were positive for at least one of the "Top 7" STEC bacteria. STEC carriage by calves was associated with environmental factors, increased calf age, region, and increased number of calves in a shared calf pen. The intraclass correlation coefficient (ρ) indicated strong clustering of "Top 7" STEC-positive calves for O157, O26, and O45 serogroups within the same pens and farms, indicating that if one calf was positive, others in the same environment were likely to be positive as well. This finding was further evaluated with whole-genome sequencing, which indicated that a single E. coli O26 clonal strain could be found in calves in the same pen or farm, but different strains existed on different farms. This study provides evidence that would be useful for designing on-farm interventions to reduce direct and indirect human exposure to STEC bacteria.IMPORTANCE Cattle are asymptomatic carriers of Shiga toxin-producing E. coli (STEC) bacteria that can cause bloody diarrhea and kidney failure in humans if ingested. New Zealand has relatively high numbers of STEC cases, and contact with cattle feces and living near cattle are risk factors for human infection. This study assessed the national prevalence of STEC in young dairy cattle by randomly selecting 102 farms throughout New Zealand. The study used a molecular laboratory method that has relatively high sensitivity and specificity compared to traditional methods. "Top 7" STEC was found in 20% of calves on 75% of the farms studied, indicating widespread prevalence across the country. By examining the risk factors associated with calf carriage, potential interventions that could decrease the prevalence of "Top 7" STEC bacteria at the farm level were identified, which could benefit both public health and food safety.

Culture-Based Quantification with Molecular Characterization of Non-O157 and O157 Enterohemorrhagic Escherichia coli Isolates from Rectoanal Mucosal Swabs of Feedlot Cattle

Enterohemorrhagic Escherichia coli (EHEC) strains are foodborne pathogens carried in the intestinal tracts of ruminants and shed in the feces. High concentrations (≥10⁴ colony-forming units [CFU]/g) of EHEC in cattle feces are associated with contamination of hides, and subsequently, carcasses and beef. Several studies using agar media have quantified O157 but few have quantified non-O157 EHEC in samples from cattle. Thus, the objective of this study was to determine the concentration of O157 and non-O157 EHEC in cattle, and to characterize the associated EHEC isolates for their virulence potential. Two hundred feedlot steers were sampled by rectoanal mucosal swab (RAMS) every 35 days over four sampling periods, and a spiral plating method using modified Possé differential agar was used to quantify EHEC organisms in these samples. Bacterial colonies from agar plates were tested by multiplex PCR for Shiga toxin and intimin genes (stx and eae, respectively), and confirmed EHEC isolates (i.e., positive for both stx and eae) were serotyped and characterized for virulence genes using a microarray. Organisms detected in this study included O26, O101, O103, O109, O121, O145, O157, and O177 EHEC, with all except O121 quantifiable and measuring within a range from 9.0 × 10² to 3.0 × 10⁵ CFU/g of RAMS sample. Organisms of the same EHEC serogroup were not detected in quantifiable concentrations from a single animal more than once. EHEC organisms most commonly detected at quantifiable levels were O26, O157, and O177. Interestingly, O26 EHEC isolates tested negative for stx₁ but positive for stx_2a. High concentrations of EHEC were detected in 11 (5.5%) of the steers at least once over the sampling period. These results indicate that in addition to O157, non-O157 EHEC are transiently present in high concentrations in the rectoanal mucosal region of cattle.

Isolation and characterization of non-O157 Shiga toxin-producing Escherichia coli from beef carcasses, cuts and trimmings of abattoirs in Argentina

Several foods contaminated with Shiga toxin-producing Escherichia coli (STEC) are associated with human diseases. Some countries have established microbiological criteria for non-O157 STEC, thus, the absence of serogroups O26, O45, O103, O104, O111, O121, and O145 in sprouts from the European Union or ground beef and beef trimmings from the United States is mandatory. While in Argentina screening for O26, O103, O111, O145 and O121 in ground beef, ready-to-eat food, sausages and vegetables is mandatory, other countries have zero-tolerance for all STEC in chilled beef. The aim of this study was to provide data on the prevalence of non-O157 STEC isolated from beef processed in eight Argentinean cattle slaughterhouses producing beef for export and local markets, and to know the non-O157 STEC profiles through strain characterization and genotypic analysis. Samples (n = 15,965) from 3,205 beef carcasses, 9,570 cuts and 3,190 trimmings collected between March and September 2014 were processed in pools of five samples each. Pools of samples (n = 3,193) from 641 carcasses, 1,914 cuts and 638 trimming were analyzed for non-O157 STEC isolation according to ISO/CEN 13136:2012. Of these, 37 pools of carcasses (5.8%), 111 pools of cuts (5.8%) and 45 pools of trimmings (7.0%) were positive for non-O157 STEC. STEC strains (n = 200) were isolated from 193 pools of samples. The most prevalent serotypes were O174:H21, O185:H7, O8:H19, O178:H19 and O130:H11, and the most prevalent genotypes were stx2c(vh-b) and stx2a/saa/ehxA. O103:H21 strain was eae-positive and one O178:H19 strain was aggR/aaiC-positive. The prevalence of non-O157 STEC in beef carcasses reported here was low. None of the non-O157 STEC strains isolated corresponded to the non-O157 STEC serotypes and virulence profiles isolated from human cases in Argentina in the same study period. The application of microbiological criteria for each foodstuff should be determined by risk analysis in order to have a stringent monitoring system. Likewise, zero-tolerance intervention measures should be applied in beef, together with GMP and HACCP. Further, collaborative efforts for risk assessment, management and communication are extremely important to improve the safety of foodstuffs.