ABSTRACT
The molecular mechanisms which allow Shigellae, and some strains of Escherichia coli, to invade the intestinal epithelium remain largely a matter of conjecture. This chapter deals with the cell biology of bacterial invasion and the possible role of the proteins in invasion. It examines the genetic organization and expression of proteins which are associated with virulence in Shigella species. Genetic analysis of virulence in Shigella species depends upon laboratory models. The HeLa cell model and the J774 cultured macrophage have proven useful in the study of invasion and subsequent intracellular bacterial growth. The advantage of the J774 macrophage involves the ability of this cell line to ingest either invasive or non-invasive Shigellae. There are two types or informational molecules on the bacterial surface which could theoretically serve as determinants of the invasive phenotype in Shigella species. These include the polysaccharide components of somatic antigens and the outer membrane proteins.
