Sub-inhibitory Concentrations of Antifungals Suppress Hemolysin Activity of Oral Candida albicans and Candida tropicalis Isolates from HIV-Infected Individuals

Secretion of hydrolytic enzymes such as hemolysin is considered an important virulence attribute of the opportunistic pathogenic fungus Candida. It is known that Candida spp. isolated from HIV-infected patients produce copious hemolysins. As common antifungal agents may perturb the production of extracellular enzymes, we evaluated the effect of three antifungals nystatin, amphotericin B and fluconazole on the hemolytic activity of Candida albicans and Candida tropicalis isolates from HIV-infected individuals. The impact of antimycotics on hemolytic activity was assessed by a previously described in vitro plate assay, after exposing ten isolates each of C. albicans and C. tropicalis recovered from HIV-infected individuals to sub-minimum inhibitory concentrations (sub-MIC) of nystatin, amphotericin B and fluconazole. All Candida isolates showed a significant reduction in hemolytic activity. The reduction was highest for amphotericin B-exposed C. albicans and C. tropicalis followed by nystatin and fluconazole. The effect of antimycotics was more pronounced on the hemolytic activity of C. tropicalis compared to that of C. albicans. Commonly used antifungal agents significantly suppress hemolysin activity of Candida species. This implies that the antifungals, in addition to their lethality, may modulate key virulence attributes of the yeast. The clinical relevance of this phenomenon in HIV disease and other similar pathologies remains to be determined.