Objective To investigate the drug resistance and genomic characteristics of Salmonella isolates from the foods and diarrhea patients in Tianshui, Gansu province, and provide evidence for surveillance and prevention of Salmonella.

Methods A total of 32 Salmonella strains were isolated in Tianshui from 2021 to 2023. The antimicrobial susceptibility testing to 13 classes of antibiotics including 29 kinds of compounds were conducted with broth micro-dilution method; and genomic characterization were analyzed for serotypes, sequence types(ST), resistance genes, virulence genes and phylogenetic relationship.

Results  In all 32 Salmonella isolates, there were 6 serogroups and 15 serotypes,16 ST types, S. Enteritidis (21.88%, 7/32), S. Typhimurium monophasic variant (15.60%, 5/32) and Salmonella Indiana (15.60%, 5/32) were the predominant serotypes, ST11, ST34 and ST17 were the predominant sequence types; Salmonella showed high rates of resistance to ampicillin(75.00%), streptomycin(65.63%), tetracycline(65.63%) and ampicillin/sulbactam (62.50%), the proportion of multidrug resistant isolates was 75.00% (24/32). The 32 strains of Salmonella carried 66 different resistant genes which belong to 12 categories, the carriage rates of the resistance genes above 50.00% were aac(6')-Iaa, aph(3'')-Ib, aph(6)-Id, tet(A) and sul2, the mutations of gyrA p.S83F, gyrA p.D87N, parC p.T57S and parC p.S80R of QRDRs were the predominant mutation types; the 32 strains of Salmonella carried 172 kinds of virulence genes and showed high rates of the virulence genes relevant to Salmonella pathogenicity island and fimbrial virulence factor; the strains of different serotypes and ST types could be distinguished by the core genome multi-locus sequence typing method, and strains with the same ST types clustered together.

Conclusion The Salmonella strains isolated from the foods and the clinical settings in Tianshui showed genetic evolutionary diversity, had serious multidrug resistance, and carried abundant resistant genes and virulence genes.