In vitro activity of fluconazole, voriconazole and caspofungin against clinical yeast isolates

Predicting the clinical outcome of a systemic mycosis is often a difficult task, especially when microbiological resistance is one of the factors contributing to therapeutic failure. Some of these factors are host-related--e.g. immune state, site and severity of infection, poor compliance to therapy--while others are associated with the drug's characteristics--e.g. dosage, type of compound (fungistatic/fungicidal), pharmacokinetic properties and drug-drug interactions. In the last few years, clinicians have been confronted with the problem of selecting the most appropriate antifungal therapy for systemic infections and have highlighted the need for a reliable method to assay the in vitro susceptibility of yeasts and molds to different antifungal agents, which would allow them to institute a tailored therapy. Using the CLSI micromethod--the reference method for clinically relevant yeast testing--we assayed 70 clinical yeast isolates ( Candida spp., collected from patients with systemic mycosis) for susceptibility against fluconazole, voriconazole and caspofungin. Data obtained from our in vitro susceptibility assays revealed good activity of azoles against the majority of Candida spp. In particular, 88.6% of the assayed isolates were susceptible to fluconazole, with minimum inhibitory concentrations (MICs) ranging from =0.125 microg/mL to 8 microg/mL; 97.1% of the isolates were susceptible to voriconazole, with MICs ranging from 0.008 microg/mL to 1 microg/mL; regarding caspofungin 72.9% of the isolates had MICs ranging from 0.25 microg/mL to 1 microg/mL.