Investigation and molecular characteristics of an outbreak caused by multidrug resistant Shigella flexneri subtype 1a infection
Objective To investigate a bacillary dysentery outbreak in a mental hospital in Jiangsu Province.Methods An epi-demiological survey was performed.Specimens were collected,isolated,cultured and identified.The isolates were subjected to antimicro-bial susceptibility test and second-generation sequencing,and the second-generation sequencing data were used for drug-resistant gene,virulence gene and phylogenetic analyses.In addition,tracing and transmission route analyses were performed based on epidemiological data.Results Six Shigella flexneri subtype 1 a isolates were obtained from 5 cases and one close contact,carrying multiple drug-resist-ant genes,including extended spectrum β-lactase resistance gene,sulfonamide resistance gene,and high-level quinolone resistance gene.Phylogenetic analysis showed that 6 S.flexneri subtype 1a isolates shared high sequence homology,and might be derived from local or neighboring cities.In addition,the difference in levels of drug resistance in S.flexneriisolatesfrom asymptomatic cases was attributed to plasmid loss.Conclusions The outbreak was caused by S.flexneri subtype 1a infections.High attention should be paid to drug-resistant S.flexneriisolates,and intensified dysentery control is required in specific places and among specific populations.In addition,second-generation sequencing and bioinformatics analysis are recommended in future epidemics surveys.
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