MICs and minimum fungicidal concentrations of amphotericin B, itraconazole, posaconazole and terbinafine in Sporothrix schenckii

Abstract

The in vitro susceptibility of 62 isolates of Sporothrix schenckii in its mycelial form, from Latin-American countries (Peru, Venezuela, Brazil and Uruguay) and Spain, to amphotericin B (AB), itraconazole (IZ), posaconazole (PZ) and terbinafine (TB) was determined by measuring the MICs and minimum fungicidal concentrations (MFCs) using a standardized Clinical and Laboratory Standards Institute method. In general, TB was the most active drug, with the lowest geometric mean (GM) MIC and MFC values amongst isolates from the five countries tested. IZ and PZ showed almost the same activity against all strains tested, except for isolates from Uruguay where IZ gave the highest GM MIC (10.68 mg l(-1)). AB showed the widest MIC range (0.03-16.0 mg l(-1)); however, this drug was less active against 79 % of isolates (MICs above 1 mg l(-1)). MFCs were 5 to 20 times higher than the MICs, but the lowest GM MFC and range values were found for TB. IZ and PZ gave the highest GM MFC. MFC may be a better predictor of therapeutic response than MIC, especially in immunosuppressed patients, making the use of IZ and PZ an inappropriate treatment. There were some differences in susceptibility according to the geographical source of the isolates, with the MIC being lower for TB in Venezuelan strains (P=0.066) and the MFC higher for PZ in Peruvian strains (P=0.02). Thus, geographical origin may be important for appropriate treatment, and may relate to the identification of species of the S. schenckii complex.