Antifungal activity of curcumin-silver nanoparticles against fluconazole-resistant clinical isolates of Candida species

Introduction: Candida species is the common form of opportunistic fungal infections, especially in immunosuppressed individuals. Fluconazole is the first-line therapy for candidiasis as it is affordable and readily available. However, the antifungal resistance pattern in high-risk patients is a major concern.

Aim: The objective of the present study was to assess the anticandidal activity of curcumin-silver nanoparticles (C-Ag-NPs) against fluconazole-resistant Candida species isolated from HIV patients.

Materials and methods: Ten milliliters of 0.1 M silver nitrate (AgNO₃) and 3 ml curcumin solution was heated in a water bath for 1 h at 60°C. The formation of the Ag-NPs was determined by color change from light yellow to brownish. The solution was centrifuged at 9000 rpm for 15 min and was washed with ethanol and later lyophilized for 24 h to obtain the purified curcumin-Ag-NPs (C-Ag-NPs). A stock of 1 mg/ml of C-Ag-NPs was prepared in deionized water. The agar diffusion test and broth dilution tests were conducted to determine the anticandidal activity of C-Ag-NPs.

Results: C-Ag-NPs showed a better antifungal activity compared to curcumin and AgNO₃ solution. Candida glabrata and Candida albicans were the most inhibited and Candida tropicalis was the least inhibited species. The mean zone diameter was 22.2 ± 0.8 mm, 20.1 ± 0.8 mm, and 16.4 ± 0.7 mm against C. glabrata, C. albicans and C. tropicalis respectively. Other Candida species under the study were also inhibited. Inhibitory activity was dose dependent and it increased with concentration. The minimum inhibitory concentration values for different Candida species ranged from 31.2 μg/ml to 250 μg/ml.

Conclusion: This is the first report on the antifungal activity of C-Ag-NPs against fluconazole-resistant Candida isolates. C-Ag-NPs can be explored further to identify a potential drug candidate that can be used for the treatment of candidiasis due to fluconazole-resistant strains of Candida species.