Identification of Fungal Species and Detection of Azole-Resistance Mutations in the Aspergillus fumigatus cyp51A Gene at a South Korean Hospital

Abstract

Purpose: With changing fungal epidemiology and azole resistance in Aspergillus species, identifying fungal species and susceptibility patterns is crucial to the management of aspergillosis and mucormycosis. The objectives of this study were to evaluate performance of panfungal polymerase chain reaction (PCR) assays on formalin-fixed paraffin embedded (FFPE) samples in the identification of fungal species and in the detection of azole-resistance mutations in the Aspergillus fumigatus cyp51A gene at a South Korean hospital.

Materials and methods: A total of 75 FFPE specimens with a histopathological diagnosis of aspergillosis or mucormycosis were identified during the 10-year study period (2006-2015). After deparaffinization and DNA extraction, panfungal PCR assays were conducted on FFPE samples for fungal species identification. The identified fungal species were compared with histopathological diagnosis. On samples identified as A. fumigatus, sequencing to identify frequent mutations in the cyp51A gene [tandem repeat 46 (TR46), L98H, and M220 alterations] that confer azole resistance was performed.

Results: Specific fungal DNA was identified in 31 (41.3%) FFPE samples, and of these, 16 samples of specific fungal DNA were in accord with a histopathological diagnosis of aspergillosis or mucormycosis; 15 samples had discordant histopathology and PCR results. No azole-mediating cyp51A gene mutation was noted among nine cases of aspergillosis. Moreover, no cyp51A mutations were identified among three cases with history of prior azole use.

Conclusion: Panfungal PCR assay with FFPE samples may provide additional information of use to fungal species identification. No azole-resistance mediating mutations in the A. fumigatus cyp51A gene were identified among FFPE samples during study period.