GENOTYPING OF SALMONELLA STRAINS ISOLATED FROM DUCKS AND THEIR ENVIRONMENTS IN PENANG, MALAYSIA USING REPETITIVE EXTRAGENIC PALINDROMIC (REP)

Abstract

Salmonella are important foodborne pathogens of worldwide concern. The objective of this study was to determine the genetic diversity of 107 Salmonella strains isolated from ducks, their rearing and processing environments in Penang, Malaysia using repetitive extragenic palindromic-polymerase chain reaction (REP-PCR). REP-PCR of the Salmonella strains produced DNA bands of different sizes for differentiation purposes. The DNA band sizes ranged from 105-7692 bp for S. Typhimurium, 116-7033 bp for S. Hadar, 127- 7399 bp for S. Enteritidis, 140-7497 bp for S. Braenderup and 123-5857 bp for S. Albany. Cluster analysis at a coefficient of 0.85 grouped the Salmonella strains into various clusters and singletons. S. Typhimurium were grouped into 4 clusters and 26 singletons at a discriminatory index (D-value) of 0.98, S. Hadar were grouped into 3 clusters and 13 singletons at a D-value of 0.914, S. Enteritidis were grouped into 3 clusters and 9 singletons at a D-value of 0.971, S. Braenderup were grouped into 2 clusters and 11 singletons at a D-value of 0.981, and S. Albany were grouped into 3 clusters and 7 singletons at a D-value of 0.978. With the exception of S. Hadar strains which were grouped into two major groups (genotypes) by REP-PCR, the rest were grouped into three major genotypes. REP-PCR successfully typed all the Salmonella strains and proved to be a useful typing tool for determining the genetic diversity of the duck Salmonella strains. Determining the genetic diversity among Salmonella strains, other foodborne pathogens and their sources of isolation is important to trace their primary or potential sources and the sources of human infection.