Analysis on Monophasic Salmonella Typhimurium drug resistance and molecular typing in Linyi city
Objective To investigate the prevalence and molecular typing of drug resistance genes in human Monophasic Salmonella Typhimurium in Linyi city,so as to provide a reference for surveillance and prevention of Monophasic Salmonella Typhimurium infections.Methods Twenty-seven strains of human-origin Monophasic Salmonella Typhimurium(from the faeces of diarrhoea patients)were collected for whole-genome sequencing in Linyi city from 2017 to 2022.MLST and cgMLST genotyping were performed in conjunction with 23 Monophasic Salmonella Typhimurium genomic data from public databases to employ prediction and classification analysis of drug resistance genes based on se-quencing data,and single-nucleotide polymorphism(snps)in all genomes were identified using NC_003197 genome as ref-erence sequence,a phylogenetic tree based on SNP loci was constructed.Results A total of 36 resistance genes of 9 classes were predicted in 27 Linyi isolates,the resistant genes were aac(6')-Iaa(27/27),aph(6)-Id(24/27),aph(3")-Ib(23/27),blaTEM-1B(16/27),sul2(20/27),tet(B)(18/27)and qnrS1(10/27),92.59％of the isolates carried 3 or more classes of resistance genes.The multilocus sequence typing showed that all 27 Linyi isolates were ST34 and were classified into 12 cgMLST types,of which 224631298 was the dominant type.No identical cgMLST type was found among the 23 strains in the public database.A total of 27 strains of Linyi,10 strains of ST34 and 2 strains of ST7832 and ST2379 were clustered in a branch of public database.Conclusion Based on the whole genome sequencing data,predictive analysis of Linyi shows that Monophasic Salmonella Typhimurium are highly resistant,the strains have significant genetic diversity,and there is a potential risk of outbreak.
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