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Volume 7, Issue 6 (Suppl) J Bacteriol Parasito
ISSN: 2155-9597 JBP, an open access journal Microbiology 2016
November 28-29, 2016
November 28-29, 2016 Valencia, Spain
7th World Congress on
Microbiology
The role of flagellar proteins in epidemic PCR-ribotype 027 (B1/NAP1) Clostridium difficile virulence
Soza Baban
University of Nottingham, UK
Clostridium difficile is a major cause of healthcare-associated infection and inflicts a considerable financial burden on healthcare
systems worldwide. Disease symptoms range from self-limiting diarrhea to fatal pseudomembranous colitis . Whilst C. difficile has two
major virulence factors, toxin A and B, it is generally accepted that other virulence components of the bacterium contribute to disease.
C. difficile colonizes the gut of humans and animals and hence the processes of adherence and colonization are essential for disease
onset. Bacteria within biofilms are protected from multiple stresses including immune responses and antimicrobial agents. Increased
antibiotic resistance and chronic recurrent infections have been attributed to the ability of bacterial pathogens to form biofilms. While
biofilms have been well studied for several gut pathogens, little is known about biofilm formation by anaerobic gut species. We have
limited understanding of how the causative bacterium C. difficile colonizes the host or how it can resist antibiotics and persist within
the gut. While persistent infections have been previously linked to biofilm-formation by pathogens, biofilm development by C. difficile
has not been characterized. Our work demonstrates the ability of this anaerobic pathogen to form complex biofilms, the involvement
of important clostridial pathways in biofilm development and perhaps a connection between formation of spores which are believed
to mediate persistence and biofilm formation. Importantly, we show that bacterial sensitivity to antibiotics is reduced in clostridial
biofilms. Biofilm formation may be a mechanism employed by C. difficile to survive in hostile environments such as the human gut.
Here we tested this hypothesis by comparing flagellated parental strains to strains in which flagella genes were inactivated using
ClosTron technology. Our focus was on a UK-outbreak, PCR-ribotype 027 (B1/NAP1) strain, R20291. We compared the flagellated
wild-type to a mutant with a paralyzed flagellum and also to mutants (fliC, fliD and flgE) that no longer produce flagella in vitro and in
vivo. Our results with R20291 provide the first strong evidence that by disabling the motor of the flagellum, the structural components
of the flagellum rather than active motility, is needed for adherence and colonization of the intestinal epithelium during infection.
The R20291 flagellar mutants adhered less than the parental strain in cell adherence in vitro model. Finally we demonstrated that in
strain R20291, flagella do play a role in colonization and adherence and that there are striking differences between C. difficile strains.
In addition, we also demonstrate that clinical C. difficile hyper virulent strain R20291, form structured biofilms in vitro with R20291
accumulating substantially more biofilm. Microscopic analyses show multiple layers of bacteria encased in a proteinaceous biofilm
matrix. Employing isogenic mutants, we show that virulence associated proteins, cwp84 and a putative quorum sensing regulator, luxS
are all required for maximal biofilm formation by C. difficile. Interestingly, a mutant in spo0A, a transcription factor that controls spore
formation was defective for biofilm formation indicating a possible link between sporulation and biofilm formation. Furthermore, we
demonstrate that bacteria in clostridial biofilms are more resistant to high concentrations of vancomycin, a drug commonly used for
treatment of CDI. Biofilm formation by C. difficile is a complex multifactorial process and may be a crucial mechanism for clostridial
persistence in the host.
J Bacteriol Parasitol 2016, 7:6 (Suppl)