Thyme essential oil nanoemulsion enhances fluconazole efficacy in resistant Candida glabrata and Candida krusei

Nikaein, Donya; Joghataei, Seyed Mehdi; Malakootikhah, Javad; Shahabi, Alireza; Alihosseini, Erfan; Khosravi, Alireza

doi:10.22034/cmm.2025.345402.1656

Thyme essential oil nanoemulsion enhances fluconazole efficacy in resistant Candida glabrata and Candida krusei

Document Type : Original Articles

Authors

Donya Nikaein ¹

Seyed Mehdi Joghataei ¹

Javad Malakootikhah ²

Alireza Shahabi ¹

Erfan Alihosseini ¹

Alireza Khosravi ¹

¹ Department of Microbiology and Immunology, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran

² Researcher and Ph.D. graduate in Nanobiotechnology, University of Tehran, Tehran, Iran

10.22034/cmm.2025.345402.1656

Abstract

Background and Purpose: Candidiasis is a common fungal infection, with increasing cases caused by resistant non-albicans species, such as Candida krusei and Candida glabrata. These species present remarkable clinical treatment challenges due to their resistance, particularly with azole antifungals, like fluconazole (FLZ). This study aimed to evaluate the antifungal potential of thyme (Thymus vulgaris) essential oil nanoemulsion (TEONE) against these resistant Candida strains, focusing on its impact on resistance gene expression and the enhancement of conventional treatment efficacy.
Materials and Methods: TEONE was formulated by combining thyme EO with Tween 80 and water using the antisolvent precipitation method to create a stable nanoemulsion. The TEON was characterized by using Scanning Electron Microscopy for morphology, dynamic light scattering for particle size, and zeta potential for stability and surface charge assessment. The antifungal activity of TEONE, Thyme EO, and FLZ was assessed against Candida strains using disk diffusion, microdilution, and checkerboard assays. The quantitative reverse transcription polymerase chain reaction was employed to evaluate the expression of resistance genes (ABC1, CDR1, and ERG11) following treatment.
Results: The Scanning Electron Microscopy revealed a predominantly spherical morphology with minimal rod-shaped particles, while Dynamic Light Scattering confirmed a mean droplet size of 134.3 nm and a polydispersity index of 0.402, indicating good dispersion. Zeta potential analysis showed a value of -78.6 mV, suggesting strong stability of nanoemulsion. The TEONE demonstrated significant antifungal activity, reducing minimum inhibitory concentration values by up to 50%, compared to Thyme EO (p<0.05). Disk diffusion tests showed larger inhibition zones for TEONE (20-25 mm), compared to Thyme EO (15-18 mm) (p<0.01). The quantitative reverse transcription polymerase chain reaction revealed that TEONE reduced CgCDR1 expression by up to 49% in Candida glabrata and downregulated ERG11 and ABC1 in Candida krusei (p<0.05).
Conclusion: While FLZ alone tended to increase resistance gene expression, combining TEONE with FLZ mitigated this effect and enhanced antifungal efficacy, indicating an additive interaction. TEONE represents a promising natural approach for enhancing antifungal treatment strategies against resistant Candida infections, offering potential benefits as an alternative or complementary therapy to conventional antifungal agents. These nanoemulsions may also allow for a reduction in the dosage of traditional drugs such as FLZ, potentially minimizing side effects and the development of resistance.

Highlights

Keywords

Candida

Fluconazole

Nanoemulsion

Resistance gene

Thyme

Subjects