Virulence System of Salmonella with Special Reference to Salmonella enterica

Abstract

Virulence system of Salmonella is very complex as many genes are involved in contributing the virulence of Salmonella . Some of the genes are involved in enhancing the invasion of organism in host defense system; some are playing their role in survival and replica- tion of organism inside the host, while some genes are involved in the production of molecules that produce the clinical symptoms of the disease. Broadly, we can classify virulence genes into two categories: genes that are located on the virulence contributing plasmid like spvc gene and genes that are chromosomal in nature like stn. On chromo-some, virulence genes are located in various clusters, which are known as Salmonella pathogenicity islands and till today seventeen pathogenicity islands have been identi- fied. The genes located on these pathogenicity islands produce several effector molecules, which assist in invasion, replication and survival of Salmonella inside the host. The role of plasmid is still not very clear, but it is presumed that the genes located on virulence plas- mids affect the intracellular growth of Salmonella in macrophages. Though lot of research work has been carried out to understand the virulence regulation system of Salmonella , still many questions are to be answered to decode the regulation of Salmonella