Antimicrobial resistance profiles of Salmonella isolates from human diarrhea cases in China: an eight-year surveilance study

Salmonella is widely known as one of the most common foodborne pathogens, and antibiotics remain effective in clinical therapies against its infections. To guide better clinical antibiotic treatment, we analyzed the antimicrobial resistance (AMR) profiles of a nation-wide collection of 36,822 Salmonella isolates derived from sporadic diarrhea cases in China from 2014 to 2021. A panel of 15 antibiotics, including 10 critically important and 5 highly important antimicrobial agents for human medicine based on the WHO CIA List, was selected for AMR surveillance. Salmonella enterica serovar Typhimurium, Enteritidis, I 4,[5],12:i:-, London, and Stanley were turns to be the top five serotypes from human diarrhea cases in China. Antimicrobial susceptibility testing revealed that the majority of the isolates (87.2%) were resistant to at least one antimicrobial agent, and 66.5% were multidrug resistant (MDR). Salmonella isolates were found to be highly resistant to ampicillin (73.4%) while sensitive to imipenem (98.73%). Over the eight years, the isolates were demonstrated generally an increase in resistance to ampicillin, chloramphenicol, trimethoprim-sulfamethoxazole, and azithromycin, but displayed varied resistance profiles in terms of serotypes. Stanley (0.66–27.18%) and Agona (0.78–45.30%) had lower resistance rates compared to Typhimurium (1.11–85.6%), Enteritidis (1.55–91.29%), and I 4,[5],12:i:- (1.02–94.28%). In conclusion, our results provide systematic data on the resistance characteristics of Salmonella isolates from human diarrhea cases in China. Furthermore, this data identifies priorities for the clinical treatments of antibiotics.