Antifungal activity of bamemacrolactine C against Talaromyces marneffei and its possible mechanisms of action

The present study aims to investigate the in vitro antifungal activity and mechanism of action of bamemacrolactine C (BAC), a new 24-membered macrolide compound, against Talaromyces marneffei. The test drug BAC initially demonstrated antifungal activity through a paper disk diffusion assay, followed by determination of the minimum inhibitory concentration value of 35.29 μg ml-1 using microdilution. The association study revealed that combination therapy exhibited additive effects (0.5 < FICI < 1.0) when combined BAC with either amphotericin B or fluconazole. A time-growth assay confirmed that treatment with 35.29 μg ml-1 of BAC completely inhibited the growth of T. marneffei and exhibited antifungal effects. Micromorphological analysis using scanning electron microscopy and transmission electron microscopy photomicrographs revealed that BAC treatment induced morphological damage in fungal cells compared to the control group. Transmembrane protein assays showed a significant reduction in the levels of Na+/K+-ATPase (P < .05) and Ca2+-ATPase (P < .01) compared to the control group. Intracellular enzyme assays demonstrated that BAC treatment significantly decreased ATP, malate dehydrogenase, and succinate dehydrogenase content (P < .01). The combination of proteomics and parallel reaction monitoring (PRM) verification indicated that BAC exhibits an antifungal mechanism against T. marneffei by downregulating ATP citric acid lyase (ACLY) levels , potentially affecting the tricarboxylic acid (TCA) cycle. Besides, the binding model of BAC and the ACLY also shows a good docking score. The findings suggest that BAC exhibits antifungal activity against T. marneffei, elucidating its multifaceted mechanism of action involving disruption of cell membranes' integrity and inhibition of intracellular enzyme activities, in which the modulation of ACLY in the TCA cycle may play an important role.