Species-Specific Antifungal Susceptibility Patterns of Scedosporium and Pseudallescheria Species

Abstract

ABSTRACTSince the separation ofPseudallescheria boydiiandP. apiospermain 2010, limited data on species-specific susceptibility patterns of these and other species ofPseudallescheriaand its anamorphScedosporiumhave been reported. This study presents the antifungal susceptibility patterns of members affiliated with both entities. Clinical and environmental isolates (n= 332) from a wide range of sources and origins were identified down to species level and tested according to CLSI M38-A2 against eight antifungal compounds. WhereasP. apiosperma(geometric mean MIC/minimal effective concentration [MEC] values of 0.9, 2.4, 7.4, 16.2, 0.2, 0.8, 1.5, and 6.8 μg/ml for voriconazole, posaconazole, isavuconazole, itraconazole, micafungin, anidulafungin, caspofungin, and amphotericin B, respectively) andP. boydii(geometric mean MIC/MEC values of 0.7, 1.3, 5.7, 13.8, 0.5, 1.4, 2.3, and 11.8 μg/ml for voriconazole, posaconazole, isavuconazole, itraconazole, micafungin, anidulafungin, caspofungin, and amphotericin B, respectively) had similar susceptibility patterns, those forS. aurantiacum,S. prolificans, andS. dehoogiiwere different from each other. Voriconazole was the only drug with significant activity againstS. aurantiacumisolates. The MIC distributions of all drugs except voriconazole did not show a normal distribution and often showed two subpopulations, making a species-based prediction of antifungal susceptibility difficult. Therefore, antifungal susceptibility testing of all clinical isolates remains essential for targeted antifungal therapy. Voriconazole was the only compound with low MIC values (MIC90of ≤2 μg/ml) forP. apiospermaandP. boydii. Micafungin and posaconazole showed moderate activity against the majority ofScedosporiumstrains.