Correlation of the in vitro antifungal drug susceptibility with the in vivo activity of fluconazole in a murine model of cerebral infection caused by Cryptococcus gattii

Abstract

Forty Cryptococcus gattii strains were submitted to antifungal susceptibility testing with fluconazole, itraconazole, amphotericin B and terbinafine. The minimum inhibitory concentration (MIC) ranges were 0.5-64.0 for fluconazole, <0.015-0.25 for itraconazole, 0.015-0.5 for amphotericin B and 0.062-2.0 for terbinafine. A bioassay for the quantitation of fluconazole in murine brain tissue was developed. Swiss mice received daily injections of the antifungal, and their brains were withdrawn at different times over the 14-day study period. The drug concentrations varied from 12.98 to 44.60 μg/mL. This assay was used to evaluate the therapy with fluconazole in a model of infection caused by C. gattii. Swiss mice were infected intracranially and treated with fluconazole for 7, 10 or 14 days. The treatment reduced the fungal burden, but an increase in fungal growth was observed on day 14. The MIC for fluconazole against sequential isolates was 16 μg/mL, except for the isolates obtained from animals treated for 14 days (MIC = 64 μg/mL). The quantitation of cytokines revealed a predominance of IFN-γ and IL-12 in the non-treated group and elevation of IL-4 and IL-10 in the treated group. Our data revealed the possibility of acquired resistance during the antifungal drug therapy.

Dynamic Interaction between Fluconazole and Amphotericin B against Cryptococcus gattii

“…The in vitro MIC values were correlated with the in vivo response to the treatment with fluconazole or amphotericin B in that study. This correlation was also demonstrated previously (19) amphotericin B was also indifferent (17). Based on the Etest, Kontoyiannis et al (15) found an antagonistic interaction between itraconazole and amphotericin B against isolates of Aspergillus fumigatus.…”

“…The plates were incubated at 35°C for 72 h (6). The MIC for fluconazole was determined visually as 80% growth inhibition, while for amphotericin B the reading was performed as 100% growth inhibition compared to the control (19). We also performed the MIC determination for fluconazole at 50% (the MIC-2 endpoint) of growth inhibition according to the CLSI method (6).…”

Management of Cryptococcus gattii meningoencephalitis

“…32 Recent epidemiological studies demonstrate that some strains of C. gattii , especially those of the VGII molecular type, have relatively low susceptibilities to fluconazole, with sustained susceptibility to voriconazole and posaconazole. 71–74 Although no reported data correlates low susceptibility to fluconazole by minimal inhibitory concentration to clinical outcomes, our experience is that these other azoles might have relatively improved activity when used during the continuation phase of therapy, during which the goal is to maintain oral azole therapy for weeks to months (average 6 months) after the patient completed the induction phase of treatment with amphotericin B-based formulations. Therefore, further research is needed to prospectively evaluate treatment outcomes of C. gattii infections and minimal inhibitory concentration values with fluconazole.…”

Treatment with pCramoll Alone and in Combination with Fluconazole Provides Therapeutic Benefits in C. gattii Infected Mice

“…This may be due to pCramoll not crossing the blood-brain barrier (Patricio et al, 2011) and not directly acting on the CNS. Meanwhile, fluconazole was present at higher concentration in the CNS after 14 days of use, reducing CFU in the brain (Mendes et al, 2010). Furthermore, pCramoll also stimulates C. gattii phagocytosis, increasing the early combat of the pathogen in the lungs.…”