Uropathogenic Escherichia coli isolates with different virulence genes content exhibit similar pathologic influence on Vero cells

Uropathogenic Escherichia coli are the major causative agent of urinary tract infection--they may simultaneously express a number of virulence factors to cause disease. The aim of this study was to investigate the relation between virulence factors content of fifteen UPEC isolates and their pathogenic potential. The isolates belonged to the five serotypes O78:K80, O114:K90, O142:K86, O164 and O157. Nine of the virulence factors have been explored, ibeA, pap, sfa/foc, cnfl, hly, fyuA, pil, ompT and traT. Virulence factors profiling of the isolates revealed a different content ranging from 22% to 100% of the virulence genes explored. The pathogenic capacity of all fifteen isolates when tested on Vero cells showed that the cytotoxicity for all tested strains on Vero cells was approximately equal and enhanced after growth in syncase broth, leading mainly to cell lysis. The toxic effects reduced slightly after heat treatment of the toxin, and greatly after formalin detoxification, but not all the deleterious effect was abolished. Endotoxin also has cytotoxic effects on Vero cells, but longer time is needed for cytolysis which is greatly diminished with formalin treatment. In conclusion, our study revealed that pathogenic strains of UPEC can exert their pathogenic effect on live cells or system with limited virulence factors gene content.