Serotypes, drug resistance and molecular typing characteristics of Salmonella strains isolated from foodborne diarrhea patients in Xingtai City

OBJECTIVE To explore the drug resistance and molecular typing characteristics of Salmonella strains isolated from the patients with foodborne diarrhea in Xingtai City between 2022 and 2024. METHODS Totally 41 strains of Salmonella were collected from the patients with foodborne diarrhea, the serotypes were identified by slide agglutination test, the minimum inhibitory concentrations (MICs) were determined by microbroth dilution method so as to analyze the drug resistance. The molecular types were confirmed through pulsed-field gel electrophoresis (PFGE) combined with BioNumerics 7.6 software. RESULTS The result of serological typing showed that totally 11 serotypes were involved among the 41 strains of Salmonella, the enteritis (29.27%) was the predominant serotype, followed by the mouse typhus (24.39%). The drug resistance rates to ampicillin, tetracycline and nalidixic acids were 73.17%, 68.29% and 53.66%, respectively; the drug susceptibility rate to meropenem was 97.56%. There was widespread multi-drug resistance, 82.93% (34/41) of the strains were drug-resistant, and 68.29%(28/41) of the strains were multidrug-resistant organisms (MDROs). Totally 38 types of banding patterns were obtained by PFGE molecular typing, with the similarity ranging between 22.40% and 97.30%; and showed a discrete distribution, indicating that the homology among the strains was low and there might be multiple infection sources. CONCLUSIONS There is widespread of serotypes of Salmonella isolated from the foodborne diarrhea patients in Xingtai area, the drug resistance rates are high, and the multi-drug resistance is severe. The PFGE types are diversified, indicating that there might be pressure on selection of antibiotics and diversified contamination sources. It is necessary to strengthen the drug resistance surveillance of Salmonella and food safety control and provide guidance for reasonable clinical use of drugs.