¹Hatay Mustafa Kemal University, Faculty of Veterinary Medicine, Department of Microbiology, TR-31060 Hatay - TÜRKİYE
² Aydın Adnan Menderes University, Faculty of Veterinary Medicine, Department of Microbiology, TR-09010 Aydın - TÜRKİYE DOI : 10.9775/kvfd.2024.32945 Salmonella Infantis is a poultry-adapted Salmonella enterica serovar that is increasingly reported in broilers and is also regularly identified among human salmonellosis cases. This study aimed to investigate the presence and distribution of virulence determinants and their antimicrobial susceptibilities of S. Infantis isolates obtained from clinical cases of broilers. In addition, selected 6 S. Infantis isolates were further characterized using whole-genome sequencing (WGS). The majority of the isolates was resistant to at least two or more antimicrobials. Only two isolates were susceptible to all antimicrobials tested. Higher rates of resistance were observed against ciprofloxacin (96.4%), tetracycline (96.4%), sulfamethoxazole-trimethoprim (76.8%), but low resistance rates to chloramphenicol (8.9%), and ampicillin (8.9%) were detected. WGS analysis revealed the presence of different resistome, but aac(6")-Iaa and tetA genes in all isolates, and mutations in gyrA and parC genes playing a role in quinolone resistance. WGS also revealed that all isolates were of sequence type 32 (ST32). Based on the presence of virulence genes, the isolates were characterized into five virulence profile. Among the examined virulence genes, invA, sopB, pipD, sifA, stn, spaN, slyA, and hilA were present in all isolates. Only one isolate had all virulence genes examined. The findings of this study provide valuable information on S. Infantis strains isolated from clinical cases of broilers and current antimicrobial resistance levels and virulence determinants. High resistance rates and the widespread occurrence of many virulence genes reveals that the isolates have significant pathogenic potential and pose a threat to public health. Keywords : Antimicrobial susceptibility, Integron, Salmonella Infantis, Virulence, Whole genome sequencing