Clonal spread of blaCTX-M-65 producing Salmonella enterica serovars detected in poultry retail meat in North Carolina, USA
Daniel F. M. Monte, Erin Harrell, Lyndy Harden, Siddhartha Thakur
Abstract
The rise of antimicrobial resistance (AMR) in Salmonella enterica poses a significant public health threat, particularly through the dissemination of extended-spectrum β-lactamase (ESBL) genes such as bla CTX-M-65 . This study investigated the prevalence, resistance profiles, and genomic characteristics of S . enterica isolates from retail poultry products in North Carolina, collected between 2020 and 2024. Among 132 isolates representing 25 serovars, 14 were identified as multidrug-resistant (MDR) strains harboring bla CTX-M-65 . Whole-genome sequencing revealed that these isolates belonged to three serovars— S . Infantis (n = 11), S . I -:r:1,5 (n = 2), and S . Senftenberg (n = 1)—with associated sequence types ST32 and ST14. Genomic analyses identified additional resistance determinants, including quinolone resistance-determining region (QRDR) mutations, and a range of mobile genetic elements, such as IncFIB(pN55391) plasmids. The genetic environment of bla CTX-M-65 was conserved, with IS 1380 - bla CTX-M-65 -IS 5 structures, highlighting its mobility potential. Phylogenetic analysis showed that isolates clustered by serovar, with strong associations to international lineages. These findings emphasize the ongoing clonal dissemination of bla CTX-M-65 and MDR Salmonella in the food supply chain, necessitating enhanced surveillance and mitigation strategies to curb the spread of resistance genes in food production environments.