The accuracy and clinical impact of the morphological identification of Aspergillus species in the age of cryptic species: A single-centre study.

Abstract

Aspergillus spp. is identified morphologically without antifungal susceptibility tests (ASTs) in most clinical laboratories. The aim of this study was to examine the clinical impact of the morphological identification of Aspergillus spp. to ensure the adequate clinical management of Aspergillus infections. Aspergillus isolates (n=126) from distinct antifungal treatment-naïve patients with aspergillosis were first identified morphologically, followed by species-level identification via DNA sequencing. An AST for itraconazole (ITC) and voriconazole (VRC) was performed on each Aspergillus isolate. Based on the genetic test results, morphology-based identification was accurate for >95% of the isolates at the species sensu lato level although the test concordance of Aspergillus spp. with low detection rates was low. The rates of cryptic species were found to be 1.2% among the isolates of A.fumigatus complex and 96.8% in the A.niger complex. Cryptic species with lower susceptibilities to antifungal drugs than sensu stricto species among the same Aspergillus section were as follows: The A.lentulus (n=1) isolates had low susceptibilities to azoles among the A.fumigatus complex species (n=86), and A.tubingensis isolates (n=18) exhibited lower susceptibility to azoles among the A.niger complex species (n=31). Diagnostic accuracy was high at the A.fumigatus and A.niger complex level. However, in the presence of cryptic species, a solely morphological identification was insufficient. Particularly, ITC and VRC might be inappropriate for aspergillosis treatment when the A.niger complex is identified morphologically because it is possible that the Aspergillus isolate is A.tubingensis.