GENOME FINGERPRINTING OF SALMONELLA-TYPHI BY PULSED-FIELD GEL-ELECTROPHORESIS FOR SUBTYPING COMMON PHAGE TYPES

The genomic DNA of 39 strains of Salmonella ty phi isolated from local residents and patients who had visited countries in the Asian region was analysed for restriction fragment length polymorphisms (RFLP). Pul sed-field gel electrophoretic (PFGE) analysis of Xba I- and Spe I-gene rated genomic restriction fragments established 22 PFGE types whereas phage typing differentiated the 39 isolates into 9 distinct phage type s. This study showed that PFGE is more discriminatory than phage typin g as it is capable of subtyping S. typhi strains of the same phage typ es. Genetic relatedness among the isolates was determined. Seven major clusters were identified at S-ABS of > 0.80 and the remaining 13 isol ates were distributed into minor clusters which were related at S-ABS of less than 0.80. In conclusion, PFGE analysis in conjunction with di stance matrix analysis served as a useful tool for delimeating common S. typhi phage types of diverse origins from different geographical lo cales and separated in time.