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

Prevalence and characterization of the seven major serotypes of Shiga toxin-producing Escherichia coli (STEC) in veal calves slaughtered in France

Shiga toxin (Stx)-producing Escherichia coli (STEC) belonging to the "top 7″ serotypes (i.e. O157:H7, O26:H11, O45:H2, O103:H2, O111:H8, O121:H19 and O145:H28) are considered as the main pathogenic enterohemorrhagic E. coli (EHEC). As ruminants, including calves, are a reservoir of pathogenic STEC, we investigated the prevalence, major virulence genes and genetic relatedness of top7 STEC in veal calves slaughtered in France, through the analysis of 500 fecal samples collected over one year. Thirty top7 STEC isolates were recovered from 28 calves. The two serotypes O103:H2 and O26:H11 accounted for 73% of STEC strains, followed by O145:H28 and O157:H7. STEC super-shedding levels were identified for two calves carrying STEC O103:H2 and O157:H7, respectively. Thirty-nine atypical enteropathogenic E. coli (aEPEC) were also recovered from calves. Overall, a prevalence of 5.6% top7 STEC-positive calves was found, thus higher than that previously determined for the French slaughtered adult cattle (1.8%), confirming the impact of animals age on STEC carriage. Most top7 STEC strains carried the stx1a subtype suggesting a low pathogenicity for humans. Seasonal variation in STEC carriage was also observed, with two peaks of higher prevalence during spring and fall. Genetic similarity of top7 STEC isolates was found for calves originating from the same fattening facilities, reflecting STEC circulation between animals kept in groups. This study indicates that veal calves grown for meat production are at higher risk of shedding top7 STEC compared to adult cattle. They thus represent ideal targets for the implementation of farm interventions aimed at reducing STEC burden in cattle and the food chain.

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.

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