Prevalence and Antimicrobial Resistance of Non-typhoidal Salmonella Enterica from Head Meat and Trim for Ground Product at Pork Processing Facilities

Pork head meat may harbor Salmonella and contaminate other carcass byproducts during harvest and fabrication. A large pork processing plant in the United States was sampled bimonthly for 11 months to determine the concentration, prevalence, seasonality, serotype diversity, and antimicrobial susceptibility of Salmonella enterica isolated from cheek meat and head trim of swine carcasses. Each collection consisted of 25 samples on 2 consecutive days in the morning and afternoon shifts, for a total of 100 cheek meat and 100 head trim samples each month. Tissues were cultured for Salmonella using restrictive media and enrichment techniques, and a subset of isolates was serotyped, analyzed for antimicrobial susceptibility, and genome sequenced. Salmonella post-enrichment prevalence did not differ ( P = 0.20) between cheek meat (63%) and head trim (66%). Post-enrichment prevalence differed ( P < 0.05) by month (January 94%; March 80%; May 54%; July 59%; September 47%; and November 55%), and by processing shift (morning 68%; afternoon 62%). The subset (n = 618) of isolates selected for serotyping yielded 21 distinct serotypes: Typhimurium (49%), Infantis (10%), Heidelberg (8%), I 4,[5],12:i- (8%), and 17 other types (≤ 5%). A total of 407 multidrug-resistant (MDR; resistance to 3 or more antibiotic classes) isolates were identified. There were 120 isolates that exhibited the penta-resistant ACSSuT phenotype. In addition, 113 isolates exhibited decreased susceptibility to ciprofloxacin (DSC; MIC ≥ 0.12 µg/mL).