Candida biofilm tolerance: Comparison of planktonic and biofilm resistance mechanisms

Abstract

Candida species are opportunistic fungal pathogens residing as commensal organisms in approximately 70% of the human population. During times of decreased immune function, Candida spp. are able to transition from harmless members of the human microbiota into pathogens capable of causing life-threatening infections boasting mortality rates as high as 50%. Commonly adhering to implanted medical devices, Candida spp. grow as highly structured biofilms with inherent resistance to antifungal drug therapies and the host immune system. A multitude of investigations have found this resistance to be multifactorial involving mechanisms associated with planktonic antifungal resistance (efflux pump activity) along with biofilm-specific mechanisms. One biofilm-specific mechanism involves the complex extracellular matrix. Components of the matrix, specifically b-glucan, mannan, and extracellular DNA, have been found to promote resistance against multiple antifungal drug classes. Here we will review molecular mechanisms contributing to Candida biofilm drug resistance.