In Vitro Susceptibility Testing of Aspergillus and Non-Aspergillus Filamentous Moulds to Antifungal Agents: Evaluation of Three Different Methods

Abstract

Aim: The aim of this study was to evaluate the suitability of Sensititre YeastOne (SYO) method for susceptibility profiles’ determination of non-Aspergillus moulds and of E-test for Aspergillus spp. and non-Aspergillus moulds, in comparison with the M38-A reference broth microdilution (BMD) method.

Material and Methods: A total of 33 clinical isolates of filamentous fungi were tested.

Results: The agreement between E-test and BMD at ± 2 dilutions was 82.4%, 83.3% and 82.4% for amphotericin B, itraconazole and voriconazole, respectively. The agreement between SYO and BMD at ± 2 dilutions was 76.5%, 66.7% and 88.2% for amphotericin B, itraconazole and voriconazole, respectively. The majority of differing results are due to higher MICs with the reference method. In particular, SYO was unable to detect some of the potentially amphotericin B resistant strains. We found that both E-test and SYO method were reproducible and served as suitable methods for antifungal susceptibility testing of moulds.

Conclusion: In conclusion, both E-test and SYO method are promising, but require further investigation to identify the optimum conditions for their use in testing of susceptibility profiles of filamentous fungi to antifungal agents.