Exploring biology of biofilm formation by Clostridium difficile and its role in gut persistence and relapse of infection – DifBioRel

Clostridium difficile is the leading cause of intestinal nosocomial post-antibiotic infections. The impact of C. difficile infection (CDI) in hospitals is considerable in terms of mortality, morbidity and disease management as well as for its social economic burden. Importantly, relapse of CDI, which occurs in more than 20% of patients after the first episode, is one of the most significant clinical issues of this disease. There is therefore an urgent need to better understand the molecular mechanisms controlling key steps of CDI including persistence of C. difficile in intestinal tract. For many bacterial pathogens, biofilm formation is linked to survival persistence, resistance to stress and antibiotics, and colonization that cause disease. Moreover, chronic bacterial infections are also often correlated to the ability of bacteria to form biofilms. Although C. difficile was shown to form single or mixed biofilms in vitro, little is known on factors involved in C. difficile biofilm formation in vivo and its consequences. By combining biofilm studies, global and targeted functional genetics and animal assays, the DifBioRel project aims to explore mechanisms involved in the C. difficile biofilm formation in response to inducers encountered in dysbiosis gut environment and to assess the impact of biofilm in the persistence of this important pathogen.
Based on strong preliminary results and in vitro and in vivo approaches developed and currently used by the 3-partner consortium we propose to i) identify and select the main stresses and/or stimuli present in the gut dysbiosis environment that induce C. difficile biofilm formation, ii) characterize the molecular mechanisms involved and iii) evaluate the contribution of the biofilm in the persistence of C. difficile in the gut and relapse of CDI.
In addition to inducers of single and mixed C. difficile biofilm formation already identified by the consortium, the three Partners P1 (Bruno Dupuy, Institut Pasteur), P2 (Claire Janoir, Université Paris Sud) and P3 (Jean-Marc Ghigo, Institut Pasteur) will cooperate to identify other potential factors varying gut dysbiosis and/or resilience of the microbiota, and triggering C. difficile biofilm formation. These will include nutritional compounds such as amino acids promoting C. difficile growth, antimicrobial peptides, sub-inhibitory concentrations of antibiotics or osmotic stresses. The molecular mechanisms involved in C. difficile biofilm formation in response to the major gut inducers will then be characterized. C. difficile biofilm-deficient mutants with no other phenotypic difference compared to the wild type will be used as controls to evaluate the role of biofilms in gut C. difficile persistence and CDI relapse. Partners 1 and 3 will investigate the cooperative interactions between C. difficile and several prominent commensal bacteria favoring C. difficile (mixed) biofilms to study the impact of the microbial community on C. difficile biofilm formation. In addition, Partners 1 and 2 will explore C. difficile biofilm formation in mono-associated mouse model and then study the in vivo dynamic of mixed-biofilm formation between C. difficile and tested intestinal commensal bacteria. Finally, the role of C. difficile biofilm formation in the relapse of CDI after antibiotherapy will be assessed. For this purpose, we will use adapted C. difficile-infected animal models mimicking dysbiosis and relapse developed by Partner 2 to test appropriate C. difficile mutants unable to form biofilm when exposed to the studied inducers.
The ambition of the DifBioRel project is to provide new insights on key C. difficile biofilm factors involved in in vivo persistence and relapse processes. Moreover, DifBioRel should lead to innovative strategies based on the use of specific inhibitors of biofilm formation and/or inducers of biofilm dispersion to limit bacterial survival, and therefore the spread and recurrence of CDI.