Role of flagella in aspects of Colstridium difficile virulence

Clostridium difficile is a major cause of health-care associated diarrhoea. It is a serious and costly public-health concern worldwide. The pathogenesis of C. difficile disease is mediated primarily by toxins A and B. However, different adhesins have been recently characterized as important colonization factors playing a role in the establishment of the first step of infection. This study investigated for the first time the role of flagella in virulence of two important C. difficile isolates; non-epidemic historical C. difficile 630 PCR-ribotype 012 and newly emerged hypervirulent C. difficile R20291 a BIINAPlI027 strain which caused large outbreaks of CDAD worldwide. Non-motile, paralyzed flagellated and non-flagellated mutant strains were created using ClosTron and Allelic-exchange mutagenesis systems. Variations in motility, flagellation and virulence phenotypes between the two strains were observed. The in vitro cell adherence model using the human colonic carcinoma Caco-2 cell- line and in vivo mouse models of colonization demonstrated that the flagellar filament structure functions as an adhesin, rather than serving as a motility device, to mediate C. difficile R20291 attachment to human colonic epithelial cells. Motile bacteria outcompete non-motile bacteria for colonizing axenic-mouse intestine in vivo. On the contrary, flagella of C. difficile 630 do not play a role in virulence (cell adhesion and intestinal colonization). The non-motile, non-flagellated mutants adhered more efficiently to Caco-2 cells and colonized mice as successfully as the wild-type. The hamster model of virulence demonstrated that the fliC mutant made in a 630 background was more virulent than the wild-type. Overall, findings from these studies indicate that the flagellum plays an important role as a virulence factor in contributing to the "hypervirulence" of C. difficile BI/NAPlI027 which causes more severe infections than historical strains of this organism.EThOS - Electronic Theses Online ServiceGBUnited Kingdo