Presence of sopE gene & its phenotypic expression among different serovars of Salmonella isolated from man & animals

Background & objectives: Salmonellae cause a spectrum of diseases in man and animals but their virulence factors responsible for induction of gastroenteritis and/or systematic infection are still poorly understood. Also, the different subspecies and serovars of Salmonella differ considerably in their virulence for man and animals. There is increasing evidence that Salmonella possesses a dedicated protein secretion system denoted type III secretion system (TTSS) that is involved in the early stage of Salmonella infection. One such TTSS is Salmonella outer protein E (SopE) that helps in the invasion of Salmonella by stimulating membrane ruffling. In the present study the presence of sopE gene and its phenotypic expression (SopE protein) among different serovars of Salmonella enterica isolated from man and animals in India was investigated. Methods: A total of 50 isolates of S. enterica belonging to 11 serovars were tested for the presence of sopE gene by polymerase chain reaction. The in vitro phenotypic expression of SopE protein was detected by Western blotting using anti-SopE serum. Results: Of the 50 isolates of S. enterica belonging to 11 serovars tested for the presence of sopE, 14 belonging to three serovars viz., Enteritidis, Gallinarum and Virchow were found to carry the sopE gene. Similarly, 13 isolates belonging to same three serovars were found to express SopE protein phenotypically as detected by Western blotting using anti-SopE serum. Interpretation & conclusion: The results indicated that sopE gene appreared to be distributed and conserved among only a few serovars of Salmonella (Enteritidis, Gallinarum and Virchow) irrespective of their source of isolation. The presence of sopE gene in Salmonella provides an important pathogenic means to invade epithelial cells