Pathogenetic characterization of non-typhoidal Salmonella in Chaozhou City,Guangdong Province in 2022
Objective To analyze the serotypes,drug resistance,and molecular epidemiological characteristics of non-typhoidal Salmonella in Chaozhou City,Guangdong Province in 2022,providing pathogenic support for the effective prevention and control of foodborne diseases.Methods In 2022,human-derived non-typhoidal Salmonella strains and food-derived strains were isolated through sentinel surveillance and food risk monitoring in Chaozhou City,Guangdong Province.The strains were subjected to serotyping,drug susceptibility testing,and whole-genome sequencing analysis.Results A total of 1 257 fecal specimens were collected for diarrhea surveillance in Chaozhou City in 2022,and 58 strains of non-typhoidal Salmonella were detected,with an isolation rate of 4.61%.Among 116 foodstuffs,2 strains of non-typhoidal Salmonella were detected,with an isolation rate of 1.72%.Early childhood was the main age group for infection(14/144,9.72%).The highest detection rate was in June(12/123,9.76%).The 58 human-derived non-typhoidal Salmonella strains were classified into 12 serotypes,with Salmonella typhimurium being the most prevalent(44/58,75.86%).In terms of drug resistance,55 strains showed resistance,with a resistance rate of 91.67%,among which ampicillin,tetracycline,chloramphenicol,and streptomycin had the highest resistance rates,76.67%,70.00%,67.67%,and 60.00%,respectively.Forty-nine strains were multi-resistant,accounting for 81.67%.From the molecular characteristics standpoint,multilocus sequence typing(MLST)divided the strains into 14 sequence typing(ST),with Salmonella typhimurium ST34 being the dominant type.Whole-genome single nucleotide polymorphism(wg-SNP)evolutionary analysis revealed high genetic heterogeneity among the studied strains,with Salmonella typhimurium clustering together and showing close evolutionary relationships to clinical samples of Salmonella enteritidis.Conclusions In 2022,the non-typhoidal Salmonella strains from Chaozhou showed a diversity of serotypes,with Salmonella typhimurium being predominant and exhibiting severe multidrug resistance.Molecular typing revealed diverse evolutionary characteristics.
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