Chloroquine sensitizes biofilms of Candida albicans to antifungal azoles

Biofilms formed by Candida albicans, a human pathogen, are known to be resistant to different antifungal agents. Novel strategies to combat the biofilm associated Candida infections like multiple drug therapy are being explored. In this study, potential of chloroquine to be a partner drug in combination with four antifungal agents, namely fluconazole, voriconazole, amphotericin B, and caspofungin, was explored against biofilms of C. albicans. Activity of various concentrations of chloroquine in combination with a particular antifungal drug was analyzed in a checkerboard format. Growth of biofilm in presence of drugs was analyzed by XTT-assay, in terms of relative metabolic activity compared to that of drug free control. Results obtained by XTT-metabolic assay were confirmed by scanning electron microscopy. The interactions between chloroquine and four antifungal drugs were determined by calculating fractional inhibitory concentration indices. Azole resistance in biofilms was reverted significantly (p < 0.05) in presence of 250 µg/mL of chloroquine, which resulted in inhibition of biofilms at very low concentrations of antifungal drugs. No significant alteration in the sensitivity of biofilms to caspofungin and amphotericin B was evident in combination with chloroquine. This study for the first time indicates that chloroquine potentiates anti-biofilm activity of fluconazole and voriconazole.

Farnesol Sensitivity of Serum Induced Yeast to Hyphae Morphogenesis: A Study on Fifty Clinical Isolates of Candida albicans.

Aim: Objective of this study was to examine farnesol sensitivity of yeast to hyphae dimorphism in clinical isolates of Candida albicans. Study Design: Variations in virulence attributes contribute to variations in pathogenicity of C. albicans. Ability to switch from yeast to hyphae morphology is an important virulence factor. Farnesol, a quorum sensing molecule is known to play an important role in the regulation of C. albicans morphogenesis. Analysis of farnesol susceptibility of yeast to hyphae conversion may reveal a factor responsible for variation in pathogenicity among clinical isolates of C. albicans. Place and Duration of Study: SCG Medical College & SGGS Memorial Hospital, and School of Life Sciences, SRTM University, Nanded, India. Duration of this study was, December 2008 to December 2010. Methodology: Fifty clinical isolates of C. albicans were recovered from body fluids (such as, sputum, blood, urine, vaginal swab, tracheal swab, throat swab, feces, pus and cerebrospinal fluid, etc.) of patients with different clinical manifestations, in the tertiary care center hospital. Presumptive identification of C. albicans was done on HiCHROM agar- Candida, while confirmation was done by Germ tube formation assay, Carbohydrate assimilation and Corn meal agar test. Serum induced yeast to hyphae morphogenesis in C. albicans was performed in 96 well plates. Recent methodology of micro broth dilution was used for farnesol susceptibility testing in fifty clinical isolates. Results: Farnesol prevented hyphae formation in a concentration dependent manner, in the range 25 to 400 μM. Inhibition of ≥ 50% hyphae was considered as significant reduction in morphogenesis. MIC70 for farnesol mediated inhibition of morphogenesis in C. albicans was at 200 μM. Mean values for percentage inhibition of morphogenesis in fifty strains was compared by analysis of variance (ANOVA). P = 0.05 was considered significant. Conclusion: Susceptibility of yeast to hyphae morphogenesis to the quorum sensing molecule farnesol, varied significantly among clinical isolates of C. albicans. We hypothesize that variation in farnesol sensitivity may be a factor responsible for variable dissemination and infection ability of C. albicans.