Roles of uropathogenic Escherichia coli pili in pathogenesis of urinary tract infection

Abstract

Uropathogenic E. coli (UPEC) strains account for 90% of all UTI and up to 50% of all nosocomial UTI. Infection is initiated when UPEC binds to the superficial epithelial cells by type 1 pili. In addition to attachment, the presence of type 1 pili can lead to bacterial invasion to bladder epithelial cells. However, P piliation of UPEC is characteristic of strains causing upper urinary tract infection as well as pyelonephritis leading to urosepsis. In this study we determine the roles of type 1 and P pili in interaction of UPEC with human polymorphonuclear leukocyts (PMNS). Type 1 and P piliated and unpiliated strains of UPEC were used for determining the effects of these adhesins on migration of neutrophils towards bacteria in Boyden chamber. The lectinophagocytosis and intracellular killing of bacteria with purified human neutrophils were estimated by counting of the number of viable bacteria in 45 min. Type 1 piliated UPEC stimulated significantly greater chemotaxis than did P piliated, unpiliated bacteria and bacteria in which the piliation was suppressed. Phagocytosis of type 1 piliated UPEC occurred in the direct and opsonin-independent manner. In contrast, P piliated and unpiliated bacteria failed to bind to PMNS. The results indicated that type 1 pili have a chemotatic effect and there was a positive correlation between type 1 piliation and bacterial killing by PMNS. In contrast, PMNS did not chemotaxis to UPEC with type P pili and unable to react with these bacteria. Therefore the expression of type P pili is critical to UPEC establishment in upper urinary tract. © 2008 Academic Journals Inc.