A subdose of fluconazole alters the virulence of Cryptococcus gattii during murine cryptococcosis and modulates type I interferon expression.

Cryptococcosis is an invasive infection caused by yeast-like fungus of the genera Cryptococcus spp. The antifungal therapy for this disease provides some toxicity and the incidence of infections caused by resistant strains increased. Thus, we aimed to assess the consequences of fluconazole subdoses during the treatment of cryptococcosis in the murine inflammatory response and in the virulence factors of Cryptococcus gattii. Mice infected with Cryptococcus gattii were treated with subdoses of fluconazole. We determined the behavior of mice and type 1 interferon expression during the treatment; we also studied the virulence factors and susceptibility to fluconazole for the colonies recovered from the animals. A subdose of fluconazole prolonged the survival of mice, but the morbidity of cryptococcosis was higher in treated animals. These data were linked to the increase in: (i) fluconazole minimum inhibitory concentration, (ii) capsule size and (iii) melanization of C. gattii, which probably led to the increased expression of type I interferons in the brains of mice but not in the lungs. In conclusion, a subdose of fluconazole altered fungal virulence factors and susceptibility to this azole, leading to an altered inflammatory host response and increased morbidity.