Abstract
Poster session 1, September 21, 2022, 12:30 PM - 1:30 PM
Objectives
Aspergillus fumigatus causes a variety of diseases in humans. The drugs recommended for treatment of Aspergillus diseases are the mold-active azole antifungals. However, a wide range of mutations in A. fumigatus confers azole resistance, which commonly involves modifications in the cyp51Agene, the target for azole antifungal drugs.
Methods
We investigated 255 clinical A. fumigatus isolates obtained from patients hospitalized at National Institutes of Health Clinical Center, Bethesda, Maryland, USA. The species-level identification of each isolate was evaluated by colony morphology, microscopic characteristics, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF), and PCR-sequencing of the β-tubulin gene. We also studied sequence-based analysis of the Cyp51A gene for the azole-resistant isolates.
The azole antifungal susceptibility profile of each isolate was initially evaluated using 4-well triazole screen plates (Microbiology Associates LLC, Rockville, MD, USA) containing itraconazole (4 μg/ml), voriconazole (2 μg/ml), posaconazole (0.5 μg/ml), and growth control. The full array of antifungal susceptibility was confirmed using microbroth dilution method according to Clinical and Laboratory Standards Institute CLSI M38-A3 guidelines.
Results
Of 255 A. fumigatus isolates, 12 grew on the wells containing azoles, indicating an azole-resistant phenotype. The results were read and recorded after 24 and 48 h of incubation at 35-37°C. Majority of our isolates had visible growth at 24 h. Sequence analysis of the CYP51A gene indicated the presence of M220K mutation in all 12 isolates and no mutations in the other isolates.
The fact that the azole resistance was found in A. fumigatus isolated from patients with previous azole exposure, underscores the possibility that prevalence of azole-resistance might be underestimated in various patient populations because in-vitro susceptibility testing of A. fumigatus is not routinely performed.
Conclusion
In conclusion, prevalence of azole resistance in clinical A. fumigatus isolates obtained from NIH patients underlying primary immunodeficiencies was 4.7%; all the resistant isolates exhibited azole-resistance mutation in Cyp51A gene.
Our finding adds to the growing list of regions where acquired resistance in A. fumigatus of is documented. Our results also indicate that 4-well triazole screen plates are a reliable tool for azole-resistance screening and the selection of isolates that require a full panel of antifungal susceptibility testing.
Collapse