Fungi and Fluoxetine: Effect of Fluoxetine on the Human Mycobiome

<p><b>Background</b>: The gut mycobiome and the role it plays in the gut-brain axis is an area of study in its infancy. Little is understood on how drugs might affect the mycobiome, and therefore the host. The Australian Bureau of Statistics reported that in 2018 around 13% of Australians suffer from anxiety, and around 10% from depression. The efficacy of treatment for these disorders is unpredictable, with just 30–40% of patients achieving remission. The gut microbiome may have a significant role in how treatment drugs are metabolised and the effect on neurotransmitters within the host. Interplay between the mycobiome and the microbiome may also affect treatment of these conditions.<br> <b>Aim</b>: The aims of this project are to provide a Minimum Inhibitory Concentration (MIC) of fluoxetine for two model strains of fungi, and to find the MIC of fluoxetine for endogenous fungal strains from human faecal samples.<br><b>Method</b>: A serial dilution assay of fluoxetine in a micropore plate was inoculated with <i>Saccharomyces cerevisiae</i> and <i>Candida albicans</i> and incubated overnight. This assay was repeated using two human faecal sample cultures.<br><b>Results</b>: Results demonstrate that fluoxetine inhibits <i>S. cerevisiae</i> at ~993 mg/L, and <i>C. albicans</i> at ~1100 mg/L. These MICs are greater than the physiological concentrations of fluoxetine, which is between 63 and 270 mg/L.<br><b>Conclusion</b>: Endogenous fungal strains are inhibited by greater concentrations of fluoxetine than physiological concentrations found in the human gut with standard dosing.</p>