Prevalence & phenotypic expression of sopB gene among clinical isolates of Salmonella enterica.

BACKGROUND & OBJECTIVE Salmonella induced enteritis is a complex phenomenon involving a number of pathogenic factors. Type III secretions play a central role in the development of Salmonella induced enteritis. One such Type III secretion protein is Salmonella outer proteinB (SopB). Reports on the prevalence of this gene among different serovars of Salmonella of Indian origin appears to be lacking. The present investigation reports on the prevalence of sopB gene and its phenotypic expression (SopB protein) among different serovars of Salmonella enterica isolated from man and animals. METHODS A total of 50 isolates of S. enterica belonging to 11 serovars isolated from cases of enteric infection in man, birds and animals were tested for the presence of sopB gene by polymerase chain reaction (PCR) using its specific primers. The in vitro phenotypic expression of SopB protein was detected by dot-ELISA using anti-SopB serum. RESULTS All the 50 isolates of S. enterica belonging to 11 were found to carry sopB gene irrespective of their serovars like Typhimurium, Enteritidis, Gallinarum, Choleraesuis, Virchow, etc., and source of isolation. Of these, 41 isolates were found to express sopB gene phenotypically as detected by dot- ELISA using anti-SopB serum. Of the different serovars, all but Gallinarum expressed Sop B protein phenotypically in vitro. INTERPRETATION & CONCLUSION Our findings indicated that sopB gene was wildely distributed and conserved among Salmonella irrespective of their serovars and source of isolation. Further work need to be done to study the factors associated with the phenotypic expression of this gene.