A Novel Hyphal Suspension Approach for MIC Testing of Mould Fungi

Abstract

Background: Filamentous fungi cause a wide range of superficial and invasive infections, and antifungal susceptibility assay is essential for guiding effective therapy. Standard broth microdilution methods rely on microconidia-based inocula; however, many clinically important moulds produce insufficient microconidia due to intrinsic characteristics or culture conditions, limiting the applicability of conventional testing and often necessitating empirical treatment. Objectives: To overcome this limitation, we developed an alternative method using precisely quantified mycelial cell suspensions for MIC determination. Methods: The method was evaluated using 115 fungal strains and compared with traditional microconidia-based testing. Results: High concordance was observed between the two approaches, with agreement rates of 90% or higher across three common dermatophytes causing tinea infections and three representative fungi responsible for invasive infections. Conclusions: This mycelial-based approach provides a reliable and practical alternative for antifungal susceptibility testing of poorly sporulating moulds and may improve the efficiency and accessibility of MIC testing in clinical laboratories.