| Salmonella, a zoonotic pathogen, poses a serious threat to human health and the development of animal husbandry. In China, multidrug resistance in Salmonella from both human and animal sources is a severe concern, with potential for cross-transmission. In 2019, 127 human fecal samples were collected from five hospitals in Henan Province. Salmonella was isolated using SS agar plates supplemented with 2 μg/mL colistin and identified via Gram staining, biochemical tests, and PCR amplification targeting the 16S rRNA and invA genes. The presence of the colistin resistance gene mcr-1 was assessed, and antimicrobial susceptibility testing using the microbroth dilution method was conducted to evaluate the strain's resistance to 15 commonly used antibiotics. Whole-genome sequencing was performed to analyze the strain’s genetic characteristics. A total of six Salmonella strains were identified (positivity rate: 4.7%), among which one was mcr-1-positive. The strain’s MIC for colistin was 8 μg/mL. MLST identified the strain as ST34. It harbored multiple resistance genes, including blaTEM-116, bla CTX-M-14, bla OXA-1, oqxAB, tet(A), floR, catB3, catA1, sul1, sul2, sul3, ant(3''), aph(3')-Ia, and dfrA12. The isolate was resistant to colistin, ampicillin, amoxicillin, ceftiofur, ceftazidime, gentamicin, spectinomycin, tetracycline, florfenicol, chloramphenicol, sulfisoxazole, sulfamethoxydiazine, enrofloxacin, and ciprofloxacin. The mcr-1-bearing plasmids were transferable and showed high similarity to previously reported IncHI2 plasmids, both in China and abroad. Strengthening infection control measures and rational antibiotic use are essential to delay the emergence of drug-resistant Salmonella strains. |
