Phenotypic and genomic characteristics of Salmonella isolates from 99,780 wet market workers in Shanghai

Résumé fourni par la source

Antimicrobial resistance (AMR) in Salmonella enterica ( S . enterica ) poses an increasing public health threat. To better understand and assess the prevalence and AMR patterns of Salmonella carried by asymptomatic individuals, whole-genome sequencing and phenotypic analysis were used to investigate the epidemiology and AMR patterns within Salmonella isolates from 99,780 wet market workers in Shanghai, China. A total of 116 Salmonella isolates (0.12%) were isolated from 99,780 wet market workers in 2023 across six districts in Shanghai, China. The predominant serovars were S . I 1,4,[5],12:i:- and S . London. Antimicrobial phenotypic tests showed that 17.24% and 11.21% of these isolates were resistant to third-generation cephalosporins and fluoroquinolones, respectively, with marked serovar disparity. The prevalence of qnrS1 , bla CTX-M-55 , mph(A) , and fosA7 was 31.03%, 5.17%, 12.93%, and 12.07% of these isolates, respectively. Phylogenetic analysis indicated that S . I 1,4,[5],12:i:- ST34 strains diversified into five distinct clades, each harboring a unique resistance gene array. Two isolates carried the tigecycline resistance gene tet (X4) that were highly homologous to plasmids from both human and porcine Salmonella in China, with tet (X4) flanked by IS CR2 and IS 1 -family elements. To our knowledge, this is the first study to uncover the prevalence (0.12%) of Salmonella among 99,780 wet market workers, and the first detection of tet (X4)-harboring Salmonella in asymptomatic carriers in Shanghai. These findings underscore the critical role of asymptomatic carriers in the community spread of resistant S . enterica and provide crucial baseline data for future genomic surveillance and control strategies.

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