Prevalence and antimicrobial resistance of nontyphoidal Salmonella enterica from head meat and trim for ground product at pork processing facilities

Authors: Wottlin, Lauren; Harvey, Roger; NORMAN, KERI - Texas A&M University; BURCIAGA, SELMA - Texas A&M University; LONERAGAN, GUY - Texas Tech University; Droleskey, Robert - Bob; Anderson, Robin

Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/21/2022
Publication Date: 7/1/2022
Citation: Wottlin, L.R., Harvey, R.B., Norman, K.N., Burciaga, S., Loneragan, G.H., Droleskey, R.E., Anderson, R.C. 2022. Prevalence and antimicrobial resistance of nontyphoidal Salmonella enterica from head meat and trim for ground product at pork processing facilities. Journal of Food Protection. 85(7):1008-1016. https://doi.org/10.4315/JFP-22-049.
DOI: https://doi.org/10.4315/JFP-22-049

Interpretive Summary: Pork meat may become contaminated with Salmonella during slaughter and processing. For this study, cheek meat and head trim were collected from a pork slaughterhouse every other month for a year. The samples were tested for concentration, prevalence, seasonality, serotype diversity, and antimicrobial susceptibility of Salmonella enterica. A total of 1,999 samples were collected. There was no difference in post-enrichment prevalence of Salmonella between cheek meat (63%) and head trim (66%). Post-enrichment prevalence differed by month (January 94%; March 80%; May 54%; July 59%; September 47%; and November 55%), and by collection shift (morning 68%; afternoon 62%). A subset of 618 isolates were serotyped: Typhimurium (49%), Infantis (10%), Heidelberg (8%), I 4,[5],12:i- (8%), and 17 other types (less than or equal to 5%). Of these serotyped isolates, a total of 407 multidrug-resistant (resistance to 3 or more antibiotic classes) isolates were identified. Prominent resistance profiles were ACSSuT, decreased susceptibility to ciprofloxacin; various resistance genes were found after whole genome sequencing. This study shows that pork cheek meat and head trim can have high prevalence rates of Salmonella of diverse types and exhibiting multidrug-resistance traits.

Technical Abstract: Pork head meat, cheek meat, and lymph nodes 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 for each collection 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 was similar (P = 0.20) for 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 collection 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 (less than or equal to 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 greater than or equal to 0.12 µg/mL). Resistance genes blaCARB, blaSHV, blaTEM, aac(6')-Ib-cr, qnrB, sul2, and dfrA were expressed in numerous MDR Salmonella isolates. These data suggest that pork products from the head may have a relatively high carriage rate of Salmonella with diverse serotypes and MDR.