Yeast Killer Fungus (YKF): characterisation of a promising antifungal compound against Candida species

Fungal infections reduce the quality of life for 1.7 billon individuals worldwide killing approximately 1.6 million people every year. Candidemia is one of the most common fungal infections in humans, established from pathogenic Candida species. About 65% of candidemia cases arise from the commensal C. albicans. Emergence of resistance to current antifungal drugs is growing concern. The Kent Fungal Group has recently identified an organism named Yeast Killer Fungus (Resinicium bicolor). The novel YKF secrets a compound that demonstrates desirable traits for a promising antifungal agent.

The aim of this Research Project is twofold: firstly, to characterise the antifungal bioactivity of the YKF compound; and secondly, to utilise biochemical approaches in order to identify the YKF compound.

Firstly, a protocol was established to routinely test the antifungal properties of the YKF compound. During this experiment, it was determined that a fresh YKF culture supernatant (s/n) reaches its full potential at 14 days when stored at optimal 20-22°C, room temperature. In comparison, YKF s/n stored in 4-5°C temperature reached maximum antifungal strength after 34 days. Suggesting room temperature YKF antifungal compound deteriorates faster. Results presented in this thesis demonstrate that the YKF s/n inhibits the cellular growth of C. albicans and other Candida species including the emerging multi-drug resistant C. auris pathogen. Importantly, results presented in this thesis strongly indicate that the YKF compound if fungicidal agent as it is able to kill C. albicans cells. This is key as current antifungal drugs are mainly fungistatic, halting microbial growth. Mass spectroscopy analysis showed that the YKF compound had close extract spectra with tomatidine, a component synthesised by the tomato plant. However, the nature of the YKF compound still remains unknown.

In conclusion, YKF expresses a strong susceptibility towards a broad range of Candida species and suitable fungicidal characteristics. Very beneficial for a future antifungal drug in the market.