温州市食源性沙门菌分子特征及耐药与毒力基因分析OA

Objective To analyze the serotype distribution,molecular typing characteristics,antimicrobial resist-ance phenotypes,and antimicrobial resistance-virulence gene profiles of foodborne Salmonella strains isolated in Wenzhou from 2023 to 2024,and to provide a scientific basis for rational drug use in clinical practice and for the prevention,control,and source tracing of foodborne diseases.Methods Salmonella strains isolated from 12 designated surveillance hospitals in Wenzhou were collected.The strains were re-identified using a microbial mass spectrometer and serotyped by slide agglutination.Representative strains of different serotypes and from different isolation periods were selected for antimicrobial susceptibility testing by the broth microdilution method and high-throughput whole-genome sequencing.Based on the sequencing data,housekeeping-gene multilocus sequence typing(MLST)and core-genome multilocus sequence typing(cgMLST)were performed,and the antimicrobial resistance genes and virulence genes carried by the strains were screened and analyzed.Results A total of 421 Salmonella strains belonging to 43 serotypes were obtained.The predominant serotypes,in descending order,were Salmonella Typhimurium(153 strains,36.34％),Salmonella Enteritidis(77 strains,18.29％),and Salmonella London(50 strains,11.88％).Antimicrobial susceptibility testing was performed on 275 representative strains,with a multidrug resistance rate of 68.36％.Among them,72 strains were resistant to seven or more classes of antimicrobial agents,accounting for 26.18％.The highest resistance rates were observed for ampicillin and tetracycline,at 68.73％and 55.64％,respectively.A phylogenetic tree was constructed based on the core genomes of the 275 strains.The results showed that Salmonella Typhimurium had high genetic diversity and formed an evolutionary cluster separate from its monophasic variant;Salmonella Enteritidis strains were generally closely related,whereas Salmonella London showed relatively large genetic distances.The 275 strains collectively carried 10 major catego-ries of virulence genes and were classified into five virulence profiles.A total of 95 antimicrobial resistance genes were detected in 185 strains of the three predominant serotypes.All strains carried aminoglycoside resistance genes,and 139 strains(75.14％)carried β-lactam resistance genes,among which the blaTEM-1 was the predominant subtype(48.65％).Conclusion The predominant serotypes of foodborne Salmonella in Wenzhou were Salmonella Typhi-murium,Salmonella Enteritidis,and Salmonella London.Multidrug resistance was prominent,and the carriage rate of antimicrobial resistance genes and virulence genes were high.Prevention and control efforts should focus on the antimicrobial resistance and virulence characteristics of the predominant serotypes.