Antifungal susceptibility of the Aspergillus viridinutans complex: comparison of two in vitro methods [PublishAheadOfPrint]

Cryptic species of Aspergillus fumigatus, including the Aspergillus viridinutans species complex, are increasingly reported as a cause of invasive aspergillosis. Their identification is clinically relevant as these species frequently have intrinsic resistance to common antifungals. We evaluated susceptibilities of 90 environmental and clinical isolates from the A. viridinutans species complex, identified by DNA sequencing of the calmodulin gene, to seven antifungals (voriconazole, posaconazole, itraconazole, amphotericin B, anidulafungin, micafungin and caspofungin) using the reference European Committee on Antimicrobial Susceptibility testing (EUCAST) method. The majority of species demonstrated elevated MICs of voriconazole (geometric mean, GM: 4.46 mg/l) and itraconazole (GM: 9.85 mg/l), and had variable susceptibility to amphotericin B (GM: 2.5 mg/l). Overall, the MICs of posaconazole and MECs of echinocandins were low. The EUCAST results were compared with the Sensititre YeastOne (YO) panels. Overall, there was 67% agreement (95% confidence interval, CI: 62–72%) between EUCAST and YO panels when read at 48 hours and 82% (95% CI: 78–86%) at 72 hours. There was a significant difference in agreement between antifungals; agreement was high for amphotericin B, voriconazole and posaconazole (70–86% at 48 hours and 88–93% at 72 hours), but was very low for itraconazole (37% at 48 hours and 57% at 72 hours). The agreement was also variable between species with the maximum agreement observed for A. felis isolates (85 and 93% at 48 and 72 hours, respectively). Elevated MICs of voriconazole and itraconazole were cross-correlated but there was no correlation between other azoles tested.

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