Mechanism of Candida Albicans Biofilm and Virulence Inhibition By A Bacterial Secreted Factor

<p>The human microbiome is a diverse polymicrobial population comprised of both fungi and bacteria. Perturbations of the normal microbiome can have a profound impact on health, including the development of infections. Exploitation of these polymicrobial interactions has the potential to provide novel treatment and prevention strategies for infectious diseases. <em>Enterococcus faecalis</em>, a Gram-positive bacterium, and <em>Candida albicans</em>, a polymorphic fungus, occupy overlapping niches as ubiquitous constituents of the gastrointestinal and oral microbiome. Both species are also amongst the most important and problematic, opportunistic nosocomial pathogens and are often co-isolated during infection. Surprisingly, these two species antagonize each other’s virulence in both nematode infection and in vitro biofilm growth.</p> <p>Herein we identify the <em>E. faecalis</em> secreted bacteriocin, EntV, as both necessary and sufficient for the reduction of <em>C. albicans</em> virulence and biofilms through the inhibition of hyphal formation, a critical virulence trait of <em>C. albicans</em>. Furthermore, we demonstrate that the EntV propeptide is proteolytically processed by the metaloprotease, GelE, in <em>E. faecalis, </em>resulting in production of a highly active peptide of 68-amino acids, EntV⁶⁸. The mature peptide effectively blocks biofilm development in multiple media conditions and disrupts pre-formed biofilms, which are resistant to current antifungal treatments. Moreover, EntV⁶⁸is efficacious against clinical strains of <em>C. albicans</em>, including azole resistant strains. Biofilm development of other pathogenic <em>Candida </em>species is also impeded by EntV⁶⁸ treatment, demonstrating the target spectrum of EntV⁶⁸ is not limited to <em>C. albicans</em>. EntV⁶⁸ is protective in the murine macrophage and oropharyngeal candidiasis (OPC) infection models at nanomolar concentrations. Epithelial invasion, inflammation, and fungal burden in the OPC model were significantly reduced in response to treatment with EntV⁶⁸. Collectively, <em>C. albicans</em> cells present in the hyphal form were greatly reduces in all models examined. Despite these profound effects, EntV⁶⁸ has no effect on <em>C. albicans</em> viability, even in the presence of significant host-mimicking stresses. EntV⁶⁸ associates with cell surface of both yeast and hyphal cells of <em>C. albicans</em> and deletion of genes involved in hyphal morphogenesis and cell wall composition abrogate the inhibitory activity in <em>C. albicans </em>biofilms. These findings demonstrate that EntV has potential as a novel antifungal agent that targets virulence rather than viability.</p>

Name thesis:degree_name

Doctor of Philosophy (PhD)

Level thesis:degree_level

Dissertation (PhD)

Year dc:date.available

2017

Authors dc:creator

• Graham, Carrie
• <p>0000-0002-2761-7225</p>

Contributors dc:contributor

• Danielle A. Garsin
• Michael C. Lorenz
• Ambro van Hoof

• Candida albicans
• Enterococcus faecalis
• polymicrobial interactions
• commensalism
• pathogenesis
• bacteriocins
• Immunology and Infectious Disease
• Medicine and Health Sciences
• Microbiology
• Pathogenic Microbiology

Repository record dc:identifier

https://digitalcommons.library.tmc.edu/utgsbs_dissertations/826

OAI identifier oai:identifier

oai:digitalcommons.library.tmc.edu:utgsbs_dissertations-1871