Role of the Serratia marcescens hemolysin Shla in the invasion of epithelial cells

DI VENANZIO, G.; GARCÍA VÉSCOVI, E.

Córdoba

Congreso; XI Congreso de Microbiología General - Sociedad Argentina de Microbiología General (SAMIGE); 2015

Sociedad Argentina de Microbiología General (SAMIGE)

Serratia marcescens is an opportunistic pathogen important for public health. However, little is known about the factors and mechanisms that contribute to Serratia pathogenesis. The ShlA hemolysin is one of the major virulence factors and is responsible for the cytotoxic effect on erythrocytes and cultured cells. A hemolysin (shlBA) mutant strain showed a greatincrease of intracellular CFUs at late times post invasion in epithelial cells. Nevertheless and in contrast to the wt strain, no mutant bacteria were detected in the culture supernatant when gentamicin was eliminated from the assay at late times p.i. In addition, over 60% of the wt Serratia-containing vacuoles (SeCV) co-localize with galectin 8, a known marker of vacuolar damage, in a hemolysin-dependent manner. However, very few bacteria were detected in the cytoplasm of infected cells. The dissemination process seems not to involve the permeabilization of the plasmatic membrane. Moreover, the actin cytoskeleton seems to play an important role during this process, evidenced by the co-localization of the mutant strain with actin filaments, at late times p.i.. On the other hand, the wt and mutant SeCV recruit VAMP7, a key molecule of the vesicle fusion machinery, at late times p.i. In addition, a functional VAMP7 is necessary to allow the progression of the infection process, as evidenced by the lack of SeCV in cells expressing a dominant negative mutant of VAMP7. Based on these findings, we propose that a) ShlA is involved in the damage of the SeCV, allowing the escape, and thus the dissemination ofthe bacteria from the host celland b) VAMP7 is required for the progression of the bacterial infection of both, wt and shlBA mutant strains.