Prevalence and Antimicrobial Resistance of Nontyphoidal Salmonella in Retail Meat in Puerto Rico: A Two-Year Study (2022–2023)

Nontyphoidal Salmonella is a leading cause of foodborne illness in the United States, with over 1.35 million infections annually, 212,500 of which are antibiotic-resistant. In Puerto Rico, 47.1% of reported foodborne illness cases are attributed to nontyphoidal Salmonella. This study reports the first National Antimicrobial Resistance Monitoring System effort to characterize the prevalence and antimicrobial resistance of nontyphoidal Salmonella in Puerto Rico's retail meats. A total of 475 fresh raw samples, including chicken and giblets, ground beef, ground turkey, ground pork, and pork chops, were collected between 2022 and 2023. Nontyphoidal Salmonella was detected in 11% of samples, with higher prevalence in poultry (15%) compared to beef (4%) and pork (0%). The most prevalent serotypes were S. Typhimurium (18%) and S. Infantis (25%). Meat imported from the United States showed greater serotype diversity than locally sourced meat. Minimum inhibitory concentrations were determined for nontyphoidal Salmonella isolates, and whole-genome sequencing was performed, and bioinformatics tools were employed to assess antimicrobial resistance profiles. High resistance rates were observed for tetracycline (59%), aminoglycosides (59%), and sulfonamides (48%). Notably, 32% of isolates had reduced susceptibility to ciprofloxacin, and 14% were resistant to ceftriaxone. Multidrug-resistant Salmonella was found in 25% of isolates, including eight MDR from imported meat and two from Puerto Rico. Mean antimicrobial resistance index values were slightly higher in meat from the United States (20%) than in local meat (19%). S. Infantis strains carrying the bla_CTX-M-65 gene and IncFIB(pN55391) plasmid replicons were identified in Puerto Rico retail meat, posing a public health risk due to resistance to extended-spectrum β-lactams and multidrug resistance. These findings highlight the need for enhanced surveillance and antimicrobial stewardship in Puerto Rico.