INVASION OF CULTURED HUMAN EPITHELIAL-CELLS BY KLEBSIELLA-PNEUMONIAE ISOLATED FROM THE URINARY-TRACT

The mechanisms which enable entry into cultured human epithelial cells by Klebsiella pneumoniae were compared with those of Salmonella typhi Ty2.K. pneumoniae 3091, isolated from a urine sample of a patient wit h a urinary tract infection, invaded human epithelial cells from the b ladder and ileocecum and persisted for days in vitro. Electron microsc opic studies demonstrated that K. pneumoniae was always contained in e ndosomes. The internalization mechanism(s) triggered by K. pneumoniae was studied by invasion assays conducted with different inhibitors tha t act on prokaryotic and eukaryotic cell structures and processes, Chl oramphenicol inhibition of bacterial uptake revealed that bacterial de novo protein synthesis was essential for efficient invasion by K. pne umoniae and S. typhi. Interference with receptor-mediated endocytosis by g-strophanthin or monodansylcadaverine and inhibition of endosome a cidification by monensin reduced the number of viable intracellular K. pneumoniae cells, but not S. typhi cells. The depolymerization of mic rofilaments by cytochalasin D inhibited the uptake of both bacteria. M icrotubule depolymerization caused by colchicine, demecolcine, or noco dazole and the stabilization of microtubules with taxol reduced only t he invasion ability of K. pneumoniae. S. typhi invasion was unaffected by microtubule depolymerization or stabilization. These data suggest that the internalization mechanism triggered by K. pneumoniae 3091 is strikingly different from the solely microfilament-dependent invasion mechanism exhibited by many of the well-studied enteric bacteria, such as entero-invasive Escherichia coli, Salmonella, Shigella, and Yersin ia strains.