Analysis of molecular typing,virulence and drug resistance features of bacterial strains in simultaneous outbreaks of paraty-phoid fever A and B
Objective To investigate the molecular typing,virulence,and drug resistance features of bacterial strains in a simultane-ous outbreak of paratyphoid fever A and B,and then provide evidence for the prevention and treatment of the simultaneous transmission of different types of paratyphoid fever.Methods The clinical data of 31 patients confirmed as paratyphoid fever in the Hospital of Xin-jiang Production and Construction Corps from September 2018 to November 2018 were retrospectively analyzed.The isolated strains were performed serotyping and drug sensitivity tests.The molecular typing and the detection of virulence and drug resistance genes were carried out by multiplex PCR,pulsed-field gel electrophoresis(PFGE),and multilocus sequence typing(MLST).Results A total of 32 strains of Salmonella paratyphi were isolated from 31 patients,with 19 strains classified as type A and 13 as type B.The intermedi-ate rates of all strains against ciprofloxacin were 100%.The molecular typing and serotyping results of 11 representative strains were consistent.The PFGE fingerprints of Salmonella paratyphi A and B were also consistent.The MLST of Salmonella paratyphi A was ST85,and that of Salmonella paratyphi B was ST86.All strains carried virulence island SPI1-SPI5 representative genes such as invA,sitC,sseL,sifA,mgtC,siiE,and sopB,and regulatory gene phoP.Salmonella paratyphi A also carried cytolethal distending toxin(CDT)genes with trimeric structure such as cdtB,pltA,and pltB.The virulence plasmid genes such as pefA,prot6E,and spvB were all negative.Conclusion The simultaneous transmission of Salmonella paratyphi A and B has the characteristics of high pathogenicity and poor sensitivity to ciprofloxacin,which should be highly concerned by clinical and laboratory personnel.
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