Distribution of virulence genes in Salmonella serovars isolated from man & animals.

BACKGROUND & OBJECTIVES Pathogenesis of Salmonellosis depends upon a large number of factors controlled by an array of genes that synergise into the actual virulence of Salmonella. A study was undertaken to observe the distribution of three such genes, namely, Salmonella enterotoxin (stn), Salmonella Enteritidis fimbrial (sef and plasmid encoded fimbrial (pef genes, among different serovars of Salmonella enterica isolated from man and animals. METHODS A total of 95 isolates belonging to S. Typhimurium (51), S. Enteritidis (36), S. Bareilly (3), and S. Paratyphi B (5) serovars were subjected to polymerase chain reaction (PCR) assay for the detection of stnl ssf and pef genes using their specific primers and the PCR products were analysed by 1 per cent agarose gel electrophoresis for the presence of the respective genes. RESULTS Varying distribution pattern of these genes was observed amongst the isolates. While, stn was found in all the 95 strains, sef was found only among the S. Enteritidis isolates. The pef gene was found to be absent in 10 isolates including the three S. Bareilly isolates. INTERPRETATION & CONCLUSION Findings indicated that the stn gene is widely distributed among Salmonella irrespective of the serovars and source of isolation. However, the sef gene appears to be serovar specific. Since the stn gene is found in all the isolates, it can be a viable target gene to explore the possibility of direct detection of Salmonella from samples from biological sources.