Modulation of phagolysosome maturation by bacterial tlyA gene product.

The pathogenic traits of TlyA proteins of Mycobacterium tuberculosis are not known. Expressions of TlyA in bacteria that do not express endogenous TlyA adhere better to RAW264.7 macrophages and get phagocytosed efficiently. The internalized bacteria avoid acidification to the extent of >65% in the case of both TlyA-expressing E. coli and M. smegmatis. Consistent with this observation, we have observed decreased co-localizaton of Lysosomal Membrane Associated Protein-1 (~35%), Early Endosomal Antigen-1 (~34%), Rab5 (~30%) and Rab7 (~35%) and enhanced colocalizaton of Rab14 (~80%) on both TlyA-expressing bacteria as well as on TlyA-coated latex beads. These results suggest that the mycobacterial TlyA, in general, can modulate phagolysosome maturation pathway immediately after entry into macrophages, while other important molecules may aid the bacterium for long-term, intracellular survival at later point of time.

Aggregative adherent strains of Corynebacterium pseudodiphtheriticum enter and survive within HEp-2 epithelial cells

Corynebacterium pseudodiphtheriticum is a well-known human pathogen that mainly causes respiratory disease and is associated with high mortality in compromised hosts. Little is known about the virulence factors and pathogenesis of C. pseudodiphtheriticum. In this study, cultured human epithelial (HEp-2) cells were used to analyse the adherence pattern, internalisation and intracellular survival of the ATCC 10700 type strain and two additional clinical isolates. These microorganisms exhibited an aggregative adherence-like pattern to HEp-2 cells characterised by clumps of bacteria with a "stacked-brick" appearance. The differences in the ability of these microorganisms to invade and survive within HEp-2 cells and replicate in the extracellular environment up to 24 h post infection were evaluated. The fluorescent actin staining test demonstrated that actin polymerisation is involved in the internalisation of the C. pseudodiphtheriticum strains. The depolymerisation of microfilaments by cytochalasin E significantly reduced the internalisation of C. pseudodiphtheriticum by HEp-2 cells. Bacterial internalisation and cytoskeletal rearrangement seemed to be partially triggered by the activation of tyrosine kinase activity. Although C. pseudodiphtheriticum strains did not demonstrate an ability to replicate intracellularly, HEp-2 cells were unable to fully clear the pathogen within 24 h. These characteristics may explain how some C. pseudodiphtheriticum strains cause severe infection in human patients.

Staphylococcal catalase regulates its virulence and induces arthritis in catalase deficient mice.

To figure out whether in vivo expression of Staphylococcal catalase could correlate with the virulence and pathogenicity of the bacteria in the catalase deficient Swiss albino mice. 3 Amino 1, 2, 4 triazole (ATZ) (2 mg/g body wt) treated catalase deficient mice were infected with virulent S. aureus and bacterial burden, antioxidant enzyme levels were estimated after 3, 5 and 10 days of infection. Arthritic scores and levels of serum uric acid in mice were also determined. ATZ treatment was found to have slowed down the clearance of bacteria from blood and their rapid elimination from spleen. Increased tissue catalase activities in the spleen and liver of ATZ pre-treated mice even after 5 days of infection suggested its bacterial origin. It was further verified by zymographic analysis. Increased swelling of joints was observed after 5 days of infection. Uric acid level was found lesser in ATZ treated mice. ATZ treatment slowed the bacterial passage from blood with a lower tissue anti-oxidant enzymes leading to induction of joint inflammation.