Pulsed Field Gel Electrophoresis And Multilocus Sequence Typing Analysis Of Shigellai Flexneri 4c Emerged Recently In China

Shigellai flexneri serotype 4c has recently emerged in China as a dominant serotype.We analysed 322 strains of S.flexneri serotype 4c isolated from diarrheal patients of Hennan province,Anhui province,Shanxi province and Gansu province from 2005 to 2006 by method of pulsed-field gel electrophoresis(PFGE)with BioNumerics software.In total,81 Notl-PFGE patterns were identified in 322 isolates, of which.band types CNJZXN11.0002 and CNJZXN11.0003 were the most prevalent. CNJZXN11.0003 was found to be predominant in Hennan province,Anhui province and Shanxi province,while CNJZXN11.0002 was dominant in Gansu province.We then studied 24 isolates of S.flexneri serotype 4c,9 strains with other serotypes of S. flexneri and 1 isolate of S.sonnie by using method of multilocus sequence typing(MLST).It was found that all 24 isolates of S.flexneri serotype 4c could be identified as a single sequence type 91,which was novel and has not been reported previously.We then found that the ST91 S.flexneri includes 7 of 9 strains of other serotypes tested in this study,including,1a,2a,and X.Based on the phylogenetic tree generated by the neighbor-joining method with 15 gene sequences from ST91, from 6 Shigellai strains with genome sequence on database available for analysis, and from 19 Shigellai strains in EcMLST database,the ST91 Shigellai was evolutionally closer to S.flexneri 2a 2457T.It may have been dominant in China for years and responsible for most cases of Shigellosis in China.