CHARACTERIZATION OF THE INVASION MECHANISM OF Serratia marcescens IN EPITHELIAL CELLS

FEDRIGO, GRISELDA; CAMPOY, EMANUEL MARTIN; COLOMBO MARIA ISABEL; VESCOVI, ELEONORA

Cordoba

Congreso; Reunion SAIB XLIV; 2008

Serratia marcescens is an opportunistic human pathogen associatedwith urinary and respiratory tract infections, endocarditis,osteomyelitis, meningitis and septicemia. This microorganismproduces numerous extracellular proteins that are predicted to play arole in the bacterial environmental adaptive capacity and pathogenicpotential. Previous reports have shown that the ShlA haemolysinand the PrtA protease are able to act as virulence factors; however,the mechanisms that Serratia employs to invade and disseminate ineukaryotic cells are presently unknown. In this work, wedemonstrate that a clinical S. marcescens isolate is able to invade,survive and multiply in the CHO epithelial cells. Confocalmicroscopy analysis revealed that intracellular bacteria colocalizewith markers of late endosomes Rab7 and Lamp1. Two hours postinfectionmotile bacteria localized into acidic compartments. Inaddition, at earlier stages after entry, S. marcescens also colocalizeswith the autophagosomal marker LC3. Inhibiting Serratia de novoprotein synthesis with chloramphenicol blocked this process. Basedon these findings, we propose that S. marcescens is able to transitthrough the endocytic pathway while it actively induces anautophagy-like process that might favour the intracellular survivaland proliferation of the bacteria inside the host.