Study Of The Molecular Epidemiological Characteristics Of Shigella And Yersinia Enterocolitica Isolated From Some Provinces In China

In this study, we applied Pulsed-Field Gel Electrophoresis (PFGE) andPolymerase Chain reaction (PCR) techniques to study the molecularepidemiological characteristics of Shigella and Yersinia enterocoliticaisolated from some provinces of China. We detected two novel kinds of enterotoxin genes: set1 gene encodingShigella enterotoxin 1 (ShET1) and sen gene encoding Shigella enterotoxin2(ShET2), to determine the prevalence of those two kinds of genes in 100 S.flexneri strains isolated from three provinces of China. We also detectedother virulence genes associated with Shigella spp.. The result shows thatthere were 97% strains having set1 gene and 96% strains having sen genewhich meant there was very high prevalence of ShET1 and ShET2 genes inShigella strains isolated from some provinces of China. We selected 101 Shigella strains isolated from Henan, Heilongjiangand Tibet provinces in 2003 and typed those strains according to PulseNetdirections by PFGE method. We obtained PFGE TIF images by using XbaIas restriction endonuclease and these images were analysed byBioNumerics(Version 4.0,Applied Maths BVBA , Belium ) softwarepackages. Dice similarity coefficient was calculated and the patterns wereclustered by unweighted pair group method using arithmeticaverages(UPGMA). The similarity coefficient was between 52.4% and100%. We got 8 clusters including 2 main clusters Sh_XbaI₃ andSh_XbaI₄ which included 93% strains by cutoff method. With 95% cutoffvalue, the main clusters were divided into 12 subclusters. Sh_XbaI₃d andSh_XbaI₃e subclusters were the main types of Henan province;Sh_XbaI₄ and Sh_XbaI₃e were the main types of Heilongjiang provinceand Sh_XbaI₃c was the main type of Tibet province. We found thatalthough every province had its main clusters, those clusters had above90% similarity coefficient. This fact meant that those dominant clones ofdifferent provinces had close relationship. The serotype of different strainsdid not well tally with PFGE cluster. 98 Yersinia enterocolitica strains isolated from livestock wereanalysed by PFGE. Those strains are epidemic strains in China, whichcontain two serotypes: O:3 and O:9. The similarity coefficient wasbetween 80% and 100%. By cutoff method, we obtained two main clusters:Ye_NotI₁ and Ye_NotI₃. By 100% cutoff value, we obtained 3subclusters and 13 subclusters in these two main clusters. The serotype andPFGE cluster had a very well correlation. The result showed that the originof epidemic strains which include 2 serotypes were two close clones, whichhad little change. In a word, our study showed the molecular epidemiologycharacterization of Shigella and Yersinia enterocolitica in China. We builtup a basic database of Shigella and Yersinia enterocolitica , which wouldgive great help to the surveillance of these two kinds of diseases.