Multiplication of Shigella flexneri within HeLa cells: lysis of the phagocytic vacuole and plasmid-mediated contact hemolysis

Abstract

Virulent strains of Shigellaflexneri invade HeLa cells with high efficiency. This crucial step in the pathogenic process is encoded by a 140-megadalton plasmid which induces phagocytosis of the bacteria by host cells. In this report we used pWR100, the virulence plasmid of S. flexneri serotype 5, and pHS4108, a 32-megadalton subclone of pWR100, to demonstrate that the plasmid is also responsible for rapid intracellular growth of the bacteria. The ability to replicate intracellularly was not correlated with induction of Shiga toxin. However, plasmid-mediated intracellular multiplication was strongly correlated with the ability of the bacteria to rapidly and efficiently lyse the phagocytic vacuole and replicate freely in the cytoplasm. Temperature-regulated plasmid-mediated contact hemolytic activity strongly correlated with both phagosomal membrane lysis and efficient intracellular multiplication. We propose this virulence plasmid-associated hemolysin to be an important factor in the invasion and proliferation of Shigella spp. in mammalian cells.

The HrpB-HrpA two-partner secretion system is essential for intracellular survival ofNeisseria meningitidis

“…The mechanism of how the meningococcal HrpB-HrpA secretion system mediated intracellular colonization events is matter for future investigation. Invasive bacteria that are able to escape from vacuoles, replicate in the host cell cytoplasm and spread to adjacent host cells do so by means of haemolytic factors and phospholipases (Sansonetti et al, 1986;Gaillard et al, 1987;Winkler and Turco, 1988;Tilney and Portnoy, 1989;Meyer et al, 1997). Remarkably, expression of Listeriolysin O in Bacillus subtilis was sufficient to convert this common soil microorganism into an intracellular parasite in vitro (Bielecki et al, 1990).…”

Galectin-3, a marker for vacuole lysis by invasive pathogens

“…This is partly due to the lack of markers associated with a disrupted, but not intact, phagosome. Currently, the methods for identifying vacuole rupture include EM analysis, usage of antibiotic markers and in the case of motile bacteria, such as Shigella and Listera, the appearance of actin comet tail (Sansonetti et al, 1986;Gouin et al, 1999;Paetzold et al, 2007). This actin tail is associated with bacteria that lysed the vacuole and are free in the cytoplasm.…”

The InhA1 metalloprotease allows spores of the B. cereus group to escape macrophages

“…Yersinia enterocolitica and Helicobacter pylori block phagocytosis by monocytes and neutrophils, allowing the pathogen to survive on the cell surface (Lian et al ., 1987;Ramarao et al ., 2000;Ramarao and Meyer, 2001). Shigella and Listeria escape into the cytoplasm where they replicate (Sansonetti et al ., 1986;Cossart and Lecuit, 1998). B. anthracis spores can germinate and escape from macrophages (Guidi-Rontani et al ., 1999;Dixon et al ., 2000;Guidi-Rontani et al ., 2001), but the mechanism and the bacterial effector responsible for spore escape remain unknown.…”