The genetic and molecular basis of bacterial invasion of epithelial cells - a review

Abstract

In this review, two of the most important virulence factors of bacterial invasion of epithelial cells (adhesion and invasion) were studied from the genetic and molecular point of view. Other virulence factors are; attachment to host cells multiplication within the host, interference with host defense systems, and damage to the host. These are the determinants of microbial pathogenicity. Animal cells in tissue cultures (in-vitro) were used to study adherence and invasive properties of pathogenic bacteria. Invasion of epithelial cells was demonstrated to be triggered by invasion plasmid antigens B, C, and D ( IpaB, IpaC and IpaD ) which is accomplished by intracellular spread gene icsA. The invasion of epithelial cells by some individual species of bacteria were also reviewed.Yersinia enterocolitica invasiveness was shown to be mediated by inv gene product, invasin. Salmonella typhi was found to have four invasion loci; inv A-D, but H genes are contained in 33kb DNA fragment. Enteropathogenic E. coli (EPEC) achieve invasion by assembly of highly organized cytoskeletal structures in the epithelial cells just beneath the adherent bacteria, while Shigella flexneri was found to harbor large plasmid which encodes or regulates some functions required for epithelial cells penetration. Generally, virulence factors in bacteria may be encoded on chromosomal DNA, bacteriophage DNA, and plasmids or transposons. Key words: Genetics, Molecular, Epithelial cells, Invasion, Pathogenicity and Virulence