Prevalence and antimicrobial susceptibility of Salmonella serovars isolated from U.S. retail ground pork

Authors: Broadway, Paul; BROOKS, CHANCE - Texas Tech University; MOLLENKOPF, DIXIE - The Ohio State University; CALLE, ALEXANDRA - Texas Tech University; LONERAGAN, GUY - Texas Tech University; MILLER, MARK - Texas Tech University; Carroll, Jeffery - Jeff Carroll; Sanchez, Nicole; WITTUM, THOMAS - The Ohio State University

Submitted to: Foodborne Pathogens and Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/20/2020
Publication Date: 3/8/2021
Citation: Broadway, P.R., Brooks, C.J., Mollenkopf, D.M., Calle, A.M., Loneragan, G.H., Miller, M.F., Carroll, J.A., Sanchez, N.C., Wittum, T.E. 2021. Prevalence and antimicrobial susceptibility of Salmonella serovars isolated from U.S. retail ground pork. Foodborne Pathogens and Disease. 18(5):364-365. https://doi.org/10.1089/fpd.2020.2853.
DOI: https://doi.org/10.1089/fpd.2020.2853

Interpretive Summary: Food safety is very important to consumers in the U.S. Salmonella is responsible for almost one million cases of foodborne illness annually. This study determined how much Salmonella was in ground pork sold at grocery stores across the country. Only 1.39% of ground pork tested contained Salmonella. Most of the bacteria was found during the Fall season. None of the isolates were resistant to antibiotics commonly used to treat human Salmonella infections. These results confirm the safety of ground pork at retail stores. This information is important for producers, consumers, and regulators as they make production and purchasing decisions.

Technical Abstract: One objective of this study was to determine overall prevalence of Salmonella in ground pork from U.S. retail stores over three seasons including both case-ready and store-ground packages. Package types collected included: overwrap, chub, modified atmosphere packaging (MAP) and other (plastic or wax paper wrapped). Because package type represents different production systems and are subject to varied microbiological government regulation and testing methodologies, both USDA-FSIS and FDA Salmonella isolation protocols were performed. Another objective of the study was to determine serotypes and antimicrobial resistance profiles of the isolates obtained from the ground pork samples. Ground pork aliquots were subjected to real-time PCR. Recovered isolates were serotyped and minimum inhibitory concentration analysis (MIC) to 15 antimicrobials was determined using micro-broth dilution. Overall prevalence of Salmonella in ground pork from the 865 samples collected was 1.39%. Prevalence was not affected by package type (P = 0.29) nor grind location (case-ready vs. store-ground; P = 0.17). Season affected Salmonella prevalence (P = 0.05) with most isolates found during fall, and there was a tendency for geographic region to affect prevalence (P = 0.07). The USDA Salmonella isolation method was more effective at recovering isolates (P = 0.01) compared to the FDA methodology and yielded a Kappa statistic of 0.26 as a measure of agreement. The serotypes isolated included: Infantis, 4,5,12:i:-, Brandenburg, Typhimurium var 5-, Seftenberg, and Johannesburg with only two packages containing multiple serotypes. No isolates were resistant to antibiotics commonly used to treat human Salmonella infections including extended spectrum cephalosporins or fluoroquinolones. While the recovery of Salmonella from retail ground pork samples was rare, S. Typhimurium (and its monophasic variant 4,5,12:i:-) which are among the most common servars recovered from human infections, were recovered. Therefore, more effective strategies to further reduce or eliminate these pathogens from retail pork products are warranted.