Pseudolaric Acid A: A Promising Antifungal Agent Against Prevalent Non- Species.

Purpose: The non (NAC) species have recently gained great importance worldwide due to the increasing proportion in causing bloodstream infections. This investigation aimed to explore the efficacy of Pseudolaric acid A (PAA, a diterpenoid derived from Pseudolarix kaempferi) and its synergistic effect with fluconazole (FLC) against NAC species, including , and .

Methods: The microdilution checkerboard assay and time-killing curves were performed to detect the antifungal efficiency. To examine the integrity of cell walls and membranes, calcofluor white stain and propidium iodide stain were used. The changes of intracellular ultrastructure in cells after treatment were observed using transmission electron microscopy. Changes in cell viability with the autophagy inhibitor 3-MA were assessed by the XTT method.

Results: It was revealed that PAA alone is effective on , and (MIC 8-128 µg/mL). Strong synergism against FLC-resistant was observed (FICI 0.07-0.281), when PAA and FLC were combined. PAA had dose-dependently detrimental effects on cell membranes. Moreover, increased vacuoles and autophagosome formation were found in exposed to PAA. And the inhibitory effect of PAA against can be relieved by autophagy inhibitor 3-MA in a certain concentration range. Ultrastructural alterations of were more pronounced under the combination of PAA and FLC, including separation of the cell membrane from the cell wall, increased number of vacuoles, and degradation of organelles.

Conclusion: These observations indicated that PAA and its combination with FLC could be a promising therapeutic candidate for treating infections caused by NAC species.