In Vitro Antifungal Activity of Thymus vulgaris Essential Oil Components Against Clinical Isolates of Candida albicans

Research on plant-derived essential oil components as antifungal agents against Candida species represents a priority area within natural products microbiology and medical mycology, with direct implications for development of plant-derived antifungal therapeutics and alternatives to conventional azoles. This study applies broth microdilution MIC determination and disk diffusion agar susceptibility testing per CLSI M27 guidelines to characterize membrane disruption and ergosterol depletion by monoterpene phenol constituents in 60 clinical Candida albicans isolates from three tertiary medical centers obtained from clinical microbiology laboratory settings across Oregon and Washington state. Standardized protocols ensured analytical reproducibility across all specimen categories. Results demonstrate that carvacrol and thymol demonstrate MIC values at or below the fluconazole MIC in 61.7% of tested clinical isolates including azole-resistant strains (p = 0.001), with 61.7% of specimens exhibiting the primary phenotype of interest. Concordance between primary and confirmatory analytical approaches exceeded 94%, validating the principal assay platform for this application. These findings advance the empirical foundation for natural products microbiology and medical mycology and carry direct implications for the design of surveillance and intervention programs targeting membrane disruption and ergosterol depletion by monoterpene phenol constituents within fluconazole-resistant and fluconazole-sensitive clinical Candida isolate collections.