Study On Single Nucleotide Polymorphisms Molecular Typing Of Salmonella Typhi And The Characterization Of Molecular Epidemiology Of Salmonella Typhimurium

Salmonella Typhi is the main pathogens of typhoid fever which still remain aspublic health problems, especially in developing countries.Typhoid fevers is also thekey prevention and treatment infectious diseases and classified as Group B infectiousdiseases in China. Molecular subtyping technologies play important roles for etiologicalanalysis in infectious diseases surveilliance, outbreak identification and sourse tracking,To relize the molecular epidemiology of Salmonella Typhi in China and other countriesvia molecular subtyping. This study were applied26gene sites of SNPs subtyping andthe standard pulse-field gel electrophoresis(PFGE) analysis of Salmonella Typhi from1959to2007in China, and compared the results with same works of other countries.The SNPs subtyping is suitable for the isolates in China,and the variant patterns of thetwo kinds of molecular typing which indicated genetic diversity among SalmonellaTyphi isolates.Salmonella Typhimurium(S.Typhimurium) is a common food-borne pathogenicbacteria, and is a leading cause of human gastroenteritis. It is important to obtain thebaseline data and the molecular characteristic of S.Typhimurium isolats with PFGE andMLVA subtyping technique for improving the capability of laboratory-based foodborneoutbreaks detection.With the application of standard pulse-field gelelectrophoresis(PFGE) and multiple loci VNTR analysis(MLVA) on PulseNetInternational network,294isolates of S.Typhimurium from seven provinces from2006to2010in China were typed. The chromosomal DNA of S.Typhimurium was digestedwith XbaⅠrestricted endonucleotidase and87PFGE patterns were observed afterpulse-field gel electrophoresis. The discrimination index (D) was0.9050for PFGE typing method.The three dominate patterns of PFGE,JPXX01.CN0001,JPXX01.CN0006and JPXX01.CN0073, included76,40and24S.Typhimurium isolateswhich were further digested with the second enzyme BlnⅠto achieve additional10,22and17patterns, respectively. For MLVA method,198variant patterns were obtained andthe D value reached0.9929, indicating the discriminatory ability of the MLVA typingmethod in S.Typhimurium was superior to PFGE. When some human and food sourceS.Typhimurium isolates from certain outbreaks were analyzed via PFGE with doubleenzymes digestion and MLVA respectively, it showed a specific cluster with theindividual method. In summary, the variant patterns showed by the two moleculartyping methods indicated genetic diversity among clinical S.Typhimurium isolates inChina. MLVA with the characterization of higher discriminatory power, time savingand easy manipulation was suitable for cluster analysis when early detecting outbreakscaused by S.Typhimurium.