Objective To investigate the serotype distribution and antimicrobial resistance characteristics of foodborne Salmonella in infectious diarrhea cases in Minhang District, Shanghai, and to provide evidence for clinical diagnosis, treatment, prevention, and control of salmonellosis.

Methods Fecal or anal swab samples were collected from foodborne diarrhea cases at sentinel hospitals between 2019 and 2023 in Minhang District of Shanghai. Salmonella was isolated, biochemically identified, and serotyped. Antimicrobial susceptibility testing was performed via the microbroth dilution method.

Results A total of 4 294 samples were collected, from which 224 Salmonella strains were isolated, with an isolation rate of 5.22%. There was no gender difference in the positive rate of Salmonella. The positive rate showed seasonal fluctuations (χ²=160.475, P<0.001), with a higher positive rate in summer and autumn than in spring and autumn. Among different occupational groups, the positive rate was the highest among retired people (7.30%) (χ²=20.023, P=0.001). Among different age groups, the positive rate was the highest among those aged 80 years and above (7.33%) (χ²=13.491, P=0.009). A total of 28 serotypes were identified, with Salmonella Enteritidis being the most predominant, followed by Salmonella Typhimurium. Among them, 154 strains were multi-drug resistant to three or more types of antibiotics (68.75%). The most common drug resistance patterns among multi-drug resistant strains were ampicillin (AMP)-ampicillin/sulbactam (AMS)-sulfamethoxazole/trimethoprim (SXT)-chloramphenicol (CHL)-tetracycline (TET)-streptomycin (STR), AMP-TET-STR and AMP-AMS-TET-STR, with 9 strains being detected in each isolates.

Conclusion The positive rate of foodborne Salmonella in Minhang District, Shanghai, is high in summer and autumn, with a higher infection rate among retired people and those aged 60 years and above being the high-risk group. It is recommended to strengthen the protection for high-risk groups, implement targeted prevention and control measures in summer and autumn to reduce the risk of infection, and pay attention to guiding clinical medication and infection control.