Pulsed field gel electrophoresis based molecular typing and epidemiologic analysis of 214 strains of Salmonella typhi isolated in Guizhou province from 1959 to 2006

Objective To examine molecular epidemiologic characteristics and similarity of 214 strains of Salmonella typhi（ S. typhi） isolated in Guizhou province from 1959 to 2006,and to provide clues for source tracking of infection and finding the route of transmission. Methods Pulsed field gel electrophoresis（ PFGE） was applied to type 214 strains of Salmonella isolates. Results According to the restriction map of Xba I,the 214 strains of S. typhi strains were classified in to 85 PFGE types. And 82 types,except for type CN0004,CN0016 and CN0018,were found in China for the first time. Among the PFGE types,there were 13 types with more than 5 strains accounting for 5. 1%,12 types with more than2 strains accounting for 15. 31%,and 60 types with more than 1 strains accounting for 70. 6%. Conclusion The PFGE types of S. typhi isolated in Guizhou province were complex,with obvious gene polymorphism,which may be the main reason to cause widely and long time typhoid epidemic in Guizhou province.