S9.3d Antivirulence drug discovery to disarm Candida albicans with metabolites from myxobacteria.

S9.3 DRUG RESISTANCE IN EMERGING PATHOGENIC FUNGI, SEPTEMBER 23, 2022, 4:45 PM - 6:15 PM: Candida albicans is an opportunistic fungal pathogen. While nearly 40%-60% of humans are colonized harmlessly by C. albicans, prolonged use of antibiotics or an immune-compromised status can lead to mucosal or deadly systemic candidiasis (Kumamoto et al., 2020). There are only three classes of antifungals available to physicians to treat and prevent severe Candidiasis. These drugs, which include polyenes, echinocandins, and azoles, protect the host by killing or inhibiting growth of C. albicans, thereby exerting a strong selective pressure toward drug resistance. : Antivirulence drugs, by contrast, target virulence traits of pathogens without affecting their growth, making drug resistance less likely to evolve. We seek to discover novel antivirulence compounds against C. albicans that keep it at, or return it to, its baseline commensal state even under conditions that support pathogenicity. : Bacteria have evolved a large repository of metabolites that can inhibit and modulate the behavior of other organisms in their environment. Clades like the predatory myxobacteria are untapped for potential antifungal and antivirulence drug discovery (Vij et al., 2021). We here screened ≈ 2800 crude extracts from myxobacteria in an in situ C. albicans-mammalian epithelial cell infection model. Typically, when oral epithelial cells (TR146) are infected by C. albicans, the fungus proliferates, forms hyphae, and invades and damages the monolayer. In our assay, we estimate the damage to epithelial cells by released lactate dehydrogenase. We also note changes to the growth and morphology of the fungus. Based on these readouts we assign antivirulence and antifungal ranks to each extract, and confirm top-ranked hits with an independent propidium iodide-based assay for host cell damage, and a colorimetric assay of fungal metabolic activity. We found that several of the top-ranked antifungal extracts also showed effects on a multi-drug resistant strain of C. auris. : Using an established pipeline, we identified several of the antifungal and antivirulent bioactive components in these extracts. After scaling the production of promising lead compounds, we will test their drugability on clinical Candida spp. strains, and identify their mode of action using large-scale Candida spp. knock-out libraries and multi-omics approaches. : Our tested extracts are likely to contain new classes of non-toxic antifungals that can potentially treat infections by multi-drug resistant fungi. We identified and confirmed several myxobacteria extracts that protected mammalian epithelial cells without severely affecting the fungus’ growth, which are, therefore, considered antivirulent. SOURCES: 1. Kumamoto, C.A., Gresnigt, M.S., Hube, B., 2020. The gut, the bad and the harmless: Candida albicans as a commensal and opportunistic pathogen in the intestine. Curr. Opin. Microbiol. 56, 7–15. https://doi.org/10.1016/j.mib.2020.05.006. 2. Vij, R., Hube, B., Brunke, S., 2021. Uncharted territories in the discovery of antifungal and antivirulence natural products from bacteria. Comput. Struct. Biotechnol. J. 19, 1244–1252. https://doi.org/10.1016/j.csbj.2021.02.003.