Molecular base of pathogenicity of Listeria monocytogenes

L. monocytogenes is one of the most invasive intracellular bacteria known. L. monocytogenes break the, intestinal barrier in hosts infected by the oral route, although the site of entry, i.e., the epithelial cells or the cells in the Peyer's patches, has yet to be elucidated. After this the bacteria are internalized by resident macrophages in which they can survive and replicate, and then are released to the cytosol after lysis of vacuole. Escape from the phagocytotic vacuole requires the expression of listeriolysin O encoded by hlyA and lisA gene. The products of two genes from operon plcA-prfA play a complementary role in virulence. Among others; products of the genes mp1, actA, plcB and the protein p60 coded by the gene lap take part in the,next cycle's stage after L. monocytogenes escape from vacuole. Protein p60 is common among all species of the Listeria kind, but the sequence of repeated aminoacids in the middle sphere which does not exist in other species, is always present in the pathogenic specie.