Abstract
To better understand the in vivo efficacy of fluconazole (FCZ), we investigated the possible synergy of fungistatic FCZ with human polymorphonuclear leukocytes (PMN) against Paracoccidioides brasiliensis(Pb). The effect of interferon-gamma (IFN-γ) and granulocyte-macrophage colony-stimulating factor (GM-CSF) in this system was also studied. For this purpose, FCZ, PMN, PMN + FCZ, PMN + IFN-γ, PMN + IFN-γ + FCZ, PMN + GM-CSF and PMN + GM-CSF + FCZ were cocultured with Pb and the cfu of Pb was measured. The antifungal effect of FCZ on yeast cells of Pb was concentration-dependent. At 0.1 µg ml−1, FCZ had no effect on the growth of Pb. At 0.2 µg ml−1FCZ showed a growth-inhibitory effect on three isolates of Pb in a long-term (120 h) assay, and at 0.6 µg ml−1or higher FCZ was fungicidal. Fungistatic concentration of FCZ (0.4 µg ml−1) acted synergistically with fungistatic PMN for killing isolate Bt-4 during the first 24 h of co-culture. Moreover, IFN-γ and GM-CSF substantially enhanced the synergistic antifungal effect of PMN and FCZ. These findings provide a better understanding of why FCZ is more efficacious in in vivomodels of paracoccidioidomycosis than is predicted by in vitrosusceptibility tests.