In vitro resistance pattern of selected antifungal azoles against Candida albicans biofilms on silicone nasogastric tube

Prolonged use of implanted medical devices has been linked with device-associated infections. Since enteral tube feeding is increasing worldwide, the present study described the morphology of Candida albicans biofilms on the surface of silicone nasogastric tube (NGT) using fluorescence microscopy. With the emergence of multidrug-resistant fungal infections, the present study assessed the susceptibility profile of the biofilms to antifungal azoles namely fluconazole, miconazole, voriconazole, and posaconazole using the standard disc diffusion method. Microscopic studies of C. albicans biofilms revealed a complex heterogeneous structure with yeast cells and hyphal elements entrenched within a polysaccharide matrix. Planktonic C. albicans cells remained susceptible with posaconazole, fluconazole, miconazole, and voriconazole. However, the fungal biofilms exhibited resistance with miconazole. There was a significant reduction in the zone of inhibition on the 24-h, 48-h, and 72-h biofilm formation with posaconazole, voriconazole, and fluconazole, respectively. Kinetic investigation on C. albicans biofilm with posaconazole revealed a zero-order kinetic profile (R2=0.9774) whereas with voriconazole exhibited a first-order kinetic profile (R2=0.9974). These findings can possibly provide information regarding the resistance of fungal biofilms with antifungal azoles. Demonstration of common biofilm features will extend the findings of this study beyond fungi to polymicrobial infections, as new information and insights will influence several disciplines ranging from environmental microbiology to pharmaceutical drug design intended for biofilm-associated infections. © The Author(s) 2019