Determining the Prevalence and Antimicrobial Susceptibility of Salmonella Serovars Isolated from U.S. Retail Ground Pork

Salmonella is a foodborne pathogen that may be associated with meat products. The goal of this project was to determine the prevalence of Salmonella in ground pork at retail, and to evaluate factors that may be associated with its prevalence. Because ground pork at retail can be regulated by two separate governing bodies, the authors wanted to measure Salmonella prevalence in case-ready packages versus store-ground pork using USDA and FDA Salmonella isolation protocols. Finally, the Salmonella isolated from the ground pork was serotyped and evaluated for antimicrobial resistance using 15 antibiotics.

Ground pork was collected from grocery stores, supermarkets, and retail establishments that sold fresh meat. Packages were collected from 12 cities in 4 different regions of the U.S. (South, East, West, and Central/Midwest) during 3 seasons (Fall, Winter/Spring, and Summer). Approximately one-half of the packages collected in each city were ground and packaged off-site (referred to as “case-ready”) and the other half were ground on-site (referred to as “store-ground”). Packages were tested for Salmonella using USDA-FSIS and FDA Salmonella isolation protocols, as well as genomic evaluation. Salmonella isolates from ground pork were additionally evaluated for antimicrobial resistance using 15 antibiotics. Finally, all Salmonella isolates were serotyped.

Overall, 1.39% of ground-pork packages were positive for Salmonella (12 of 865 packages). There was no difference in Salmonella prevalence between case-ready and store-ground pork or between package types (overwrap, chub, MAP, or other). More Salmonella was isolated during the Fall season that any other season, and there was a tendency for increased prevalence in the East region. The USDA-FSIS method was a more effective method to isolate Salmonella compared to the FDA isolation protocol. None of the isolates were resistant to antibiotics used to treat Salmonella infections, such as extended spectrum cephalosporins or flouroquinolones. Six different serotypes were isolated, and only two packages contained multiple Salmonella serotypes.

The results of this study indicate the observed prevalence of Salmonella in ground pork products was low. Moreover, a clear majority of the Salmonella serotypes were broadly susceptible to the antibiotics tested and none of the serotypes were resistant to critically important antibiotics used in human medicine. Finally, these results indicate the pork industry should continue to utilize technologies and practices to reduce pathogens in pork products.