Comparative evaluation of multilocus variable-number tandem-repeat analysis and pulsed-field gel electrophoresis for genotyping Salmonella enterica serovar Typhi isolates

Objective To evaluate the capability of multilocus variable-number tandem-repeat （VNTR） analysis （MLVA） and pulsed-field gel electrophoresis （PFGE） for genotyping Salmonella enterica serovar Typhi （ S. Typhi） isolates. Methods Five polymorphic VNTRs （ SAL02, SAL11, SAL16, SAL20, and TR4699 ） that were observed in S. Typhi strains from previous studies were selected to establish MLVA. Twenty-one epidemiologically unrelated S. Typhi strains that were isolated from Shenzhen, China from 2002 to 2007 were genotyped by the established MLVA, and the results were compared with those by PFGE. Results The Simpson＇s index of diversity （D value） for all five different VNTRs ranged from 0. 838 to 0. 943. A total of 19 MLVA profiles and 19 PFGE profiles were found, respectively. The D value for both MLVA and PFGE were 0. 99 and the test results from two analyses were identical. Conclusion The five polymorphie VNTRs analysis could be used as an alternative typing scheme for epidemiologic investigation of S. Typhi infection. Key words: Salmonella enterica serovar Typhi ;  Genotyping;  Muhilocus variable-number tandem-repeat analysis; Pulsed-field gel electrophoresis