Antimicrobial resistance and virulence profiling of waterfowl-derived Salmonella in Sichuan from 2021 to 2023

This study investigated 144 Salmonella isolates obtained from 594 waterfowl samples across eight regions in Sichuan Province, China (2021–2023). Whole-genome sequencing and molecular analyses identified seven serovars, predominantly S. Typhimurium (47.2%) and S. Indiana (33.3%), and nine sequence types, mainly ST19 and ST17. All isolates showed multidrug resistance, with universal resistance to streptomycin, gentamicin, sulfamethoxazole, trimethoprim-sulfamethoxazole, erythromycin, and florfenicol, and high resistance to fluoroquinolones, lincosamides, and chloramphenicol. The aminoglycoside gene aac(6′)-Iaa was present in all isolates, while β-lactamase genes bla_CTX-M-65 and bla_OXA-1 were common in S. Indiana. Importantly, the study reports the first detection in China of ST516 Salmonella (serovar Give) from waterfowl and the cfr resistance gene in Salmonella, indicating potential spread of this multidrug-resistant lineage through mobile genetic elements and raising public health concerns.