Non-O157 Shiga Toxin-producing Escherichia Coli(STEC), campylobacter and, salmonella prevalence in ground beef and whole muscle beef cuts at retail in the United States
Vipham, Jessie L.
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Salmonella, Campylobacter, Non-O157 STEC cause considerable human illnesses each year, and the vast majority of cases are food borne. Currently, very little is known about the burden of these pathogens in the U.S. beef supply. The purpose of this study was to establish the prevalence of Campylobacter, Salmonella, and Non-O157 STEC in beef products collected from U.S. retail markets. Sample collection occurred during the months of February through May, 2010. Thirty two American cities comprising 28 states were sampled in this study. Retail raw ground and whole muscle beef (n = 2,915) samples were purchased and examined for the presence of Salmonella. Samples were enriched in tryptic soy broth (TSB) and incubated for 24 h at 37°C. Salmonella positives were confirmed using the AOAC approved BAX® system rtPCR. Of the original samples purchased, 1,211 were randomly selected and tested for Campylobacter. Positive samples were confirmed through direct plating and latex agglutination. Samples were enriched using Bolton Broth incubated for 48 h at 42°C and grown on blood-free Campylobacter plates in required microaerophilic conditions. A sub-sample (n = 325) were enriched in TSB and glycerol (TSB+glyc) and frozen at -80°C to be analyzed at a later date. Samples were screened for putative non-O157 STEC using rtPCR methods. Salmonella was detected in 0.65% of the total samples purchased. The prevalence for whole muscle cuts was 1.02%, and Salmonella was present in 0.54% of ground beef samples. Campylobacter was recovered from 9.3% of samples (n = 112), with a prevalence of 17.24% in whole muscle cuts and 7.35% in ground beef. Putative non-O157 STEC antigens were detected in 5.9% of samples. Whole muscle cuts had a prevalence of 4.11%, and ground beef sample prevalence was 6.99%. The most common serotypes detected in this study were O26 (3.8%), O145 (2.2%), O103 (1.3%), and O111 (0.98%). A chi-square analysis was conducted using the FREQ procedure of SAS. A greater percentage of O26 was observed compared to O111 and O103 (P = 0.01 and P = 0.04, respectively); however, no other comparisons between putative non-O157 STEC were significant (P > 0.05). Whole muscle cuts had a higher prevalence of Campylobacter compared to ground beef (P < 0.01),; however, comparisons between whole muscle cuts and ground beef for the other two pathogens were not significant (P > 0.05). Creating pathogen baselines in U.S. retail beef is imperative for targeting interventions for pathogen control. These data can be utilized for a more complete understanding of these pathogens and their impact on public health from the consumption of beef products.