Role of fibronectin-binding protein A in Clostridium difficile intestinal colonization

Abstract

EA 4043, USC INRA 'Ecosystè me microbien digestif et santé ', Faculté de Pharmacie, Université Paris-Sud 11, Châ tenay-Malabry, FranceClostridium difficile is a frequent cause of severe, recurrent, post-antibiotic diarrhoea and pseudomembranous colitis. Its pathogenicity is mediated mainly by two toxins, TcdA and TcdB. However, different adhesins have also been described as important colonization factors which are implicated in the first step of the intestinal infection. In this study, we focused our interest on one of these adhesins, fibronectin-binding protein A (FbpA), and on its role in the intestinal colonization process. A mutant of FbpA (CDDFbpA) was constructed in C. difficile strain 630Derm by using ClosTron technology. This mutant was characterized in vitro and in vivo and compared to the isogenic wild-type strain. Adhesion of the CDDFbpA mutant to the human colonic epithelial cell line Caco-2 and to mucus-secreting HT29-MTX cells was examined. Surprisingly, the CDDFbpA mutant adhered more than the wild-type parental strain. The CDDFbpA mutant was also analysed in three different mouse models by following the intestinal implantation kinetics (faecal shedding) and caecal colonization (7 days post-challenge). We showed that in monoxenic mice, CDDFbpA shed C. difficile in faeces at the same rate as that of the isogenic wild-type strain but its colonization of the caecal wall was significantly reduced. In dixenic mice, the shedding rate was slower for the CDDFbpA mutant than for the isogenic wildtype strain during the first days of infection, but no significant difference was observed in caecal colonization. Similar rates of intestinal implantation and caecal colonization were observed for both strains in assays performed in human microbiota-associated mice. Taken together, our data suggest that FbpA plays a role in intestinal colonization by C. difficile. INTRODUCTIONClostridium difficile is an emerging nosocomial pathogen of increasing importance and virulence, especially with the appearance of hypervirulent strains in the last few years. It is the major cause of pseudomembranous colitis and causes 15 -20 % of antibiotic-associated diarrhoea cases associated with the use of antibiotic treatment (Cartman et al., 2010;Poxton et al., 2001). Antibiotics disrupt the normal intestinal microbiota, allowing C. difficile to colonize the gut. The pathogenesis of C. difficile infections has been attributed to two toxins, TcdA and TcdB, which act as glycosyltransferases and modify small GTPases of the Rho protein family within the host cell, resulting in alterations in the cytoskeleton (Genth et al., 2008;Voth & Ballard, 2005). Apart from these two toxins, a binary toxin is also produced by a few strains but little is known about the other virulence factors which are involved in the colonization process. Presently, only a few cell surface proteins have been identified and characterized. These proteins include the S-layer proteins (Calabi et al., 2002;Cerquetti et al., 2000), the flagellum and its components (Tasteyr...

The HtrA-Like Protease CD3284 Modulates Virulence of Clostridium difficile

“…It is unclear whether this is a consequence of more diligent screening or a consequence of acquisition of additional virulence traits by the bacteria. The refractory nature of the organism to genetic manipulation has limited opportunities to investigate the roles of many genes in the control of virulence traits, including the two large clostridial toxins, the binary toxin, and other factors that contribute to the virulence of C. difficile, such as those affecting colonization and survival of the bacteria in the host (15,16,18,19). In multiple organisms, HtrA-like foldase/proteases play a considerable role in virulence by controlling protein homeostasis (21,22,26,52,65).…”

“…The contribution of the sporulation and adhesion phenotypes of the htrA mutant of C. difficile to virulence therefore awaits validation in a model other than the hamster, in which toxin production is so dominant that observation of changes to other traits can be limited. For example, analysis of this mutant in mice, which can be colonized but are less susceptible to toxin production, may be a good alternative to study the effects of htrA on colonization, transmission, and persistence (15,35).…”

“…Presently, several surface proteins have been identified or hypothesized to play a role in colonic adhesion. These include the fibronectin-binding protein A (15), S-layer proteins (16), Cwp84 (17), flagellar proteins (18), and CD1581 (19).…”

Multiple Factors Modulate Biofilm Formation by the Anaerobic Pathogen Clostridium difficile

“…Mice immunized with C. difficile surface proteins demonstrated reduced intestinal colonization with C. difficile (16). Recently, the fibronectin-binding adhesin protein A was shown to play a role in C. difficile colonization (17). The high-and low-molecular-weight surface layer proteins (SLPs) are predicted to be involved in adherence of C. difficile to host cells during the infection (18,19).…”

ClosTron-Mediated Engineering of Clostridium

“…By way of example, it has been used to establish the role of bacterial factors (toxins, flagella and adhesins) in infection, 23,[26][27][28][29] to garner a greater understanding of the role and activities of enzymes in primary metabolism, [30][31][32][33] to begin to elucidate mechanistic details of the developmental process of spore formation/ germination 21,34,35 and provide fundamental information on regulatory processes important in virulence factor and metabolite production. [36][37][38][39] Its availability has provided the research community with a sequence of the re-targeted region used to generate the insertion should be given.…”