Author:
MJ Iglesias-Cabezas1,2*, J Lucio5, I González-Jiménez5, N Román1, M Estopiña-Antolí3, J Ayats1,4, MJ Buitrago5, E Mellado4,5
Author address:
1Microbiology Department, Hospital Universitari de Bellvitge, Barcelona, Spain
2Department of Pathology and Experimental Therapeutics, IDIBELL, Universitat de Barcelona, Barcelona, Spain
3Pharmacy Department, Hospital Universitari de Bellvitge, Barcelona, Spain
4Spanish Network for Research in Infectious Diseases, REIPI RD12/0015, Madrid, Spain
5Mycology Reference Laboratory, National Centre for Microbiology, Instituto de Salud Carlos III, Madrid, Spain
Full conference title:
10th Advances Against Aspergillosis and Mucormycosis
Date: 2 February 2022
Abstract:
Purpose:
Currently, voriconazole and more recently isavuconazole are widely used for the treatment of aspergillosis. Two different routes of azole resistance development in A. fumigatus have been described: a medical route in which azole resistance is generated during long periods of azole treatment in clinical settings and another route of resistance derived from environmental origin due to extended use of DMIs in agriculture. In the first setting, the described azole resistant mechanism are mainly due to point mutations in cyp51A (G54, P216L, M220 and G448). In the environmental route, A. fumigatus showing azole resistant mechanisms with combined cyp51A modifications (TR34/L98H or TR46/Y12F/A289T) are generally isolated. A total of 116 A. fumigatus strains isolated from 57 patients were studied. All patients had at least two isolates and were or not under azole treatment.
Methods:
The ITS regions and the b-tubulin sequence analysis were indicative of an A. fumigatus sensu stricto isolates. Antifungal susceptibility testing was performed using a four wells screening methodology to detect A. fumigatus azole resistant. Positive hits were confirmed by microdilution assay following the EUCAST methodology. cyp51A was PCR amplified and sequenced. All the strains were genotyped following the typing method TRESPERG.
Results:
Six A. fumigatus strains isolated from two different patients were studied further. Patient A: Four Aspergillus fumigatus isolates were serially recovered after one month of isavuconazole (ISV) therapy from a patient suffering pulmonary aspergillosis. EUCAST susceptibility testing showed different patterns of azole susceptibility: initial and second isolates showed full azole drugs susceptibility, the 3rd isolate was highly resistant to voriconazole (VRC), posaconazole (POS) and susceptible to itraconazole (ITC) and the 4th isolate showed an uncommon pattern with high MICs to VRC and ISV (2 mg/L) but susceptibility to ITC and POS (MIC of 1 and 0.125 mg/L, respectively). The molecular analysis of cyp51A indicated that the 3rd strain has the TR46/Y121F/T289A mutations at cyp51A and the 4th has a single Y121H substitution without the TR46 or T289A alterations, which to our knowledge has never been reported. All four isolates were genotyped and presented different genotypes which indicates that the patient was infected
with a mixture of A. fumigatus strains and that resistant strains were selected due to ISV treatment. Patient B: Two A. fumigatus isogenic isolates were recovered after five months of VRC therapy, from a patient suffering pulmonary aspergillosis. The initial isolate showed full azole drugs susceptibility but the 2nd showed a pattern of high MICs to VRC and ISV (2 mg/L) but susceptibility to ITC and POS (MIC of 1 and 0.125 mg/L, respectively). The molecular analysis of cyp51A indicated that the 2nd strain showed a single Y121F substitution without the TR46 or T289A alterations too.
Conclusion:
These findings suggest a novel resistance mechanism mediated by a mutation in Cyp51A (Y121F/H) conferring high MICs only to VRC and ISV. This novel single point mutation seems to be selected by ISV or VCR treatment and might represent a ‘missing link’ between the wild-type A. fumigatus and the fully azole-resistant strain harboring the TR46/Y121F/T289A mutations.
Abstract Number: 55
Conference Year: 2022
Link to conference website: https://aaam2022.org/
URL Conference abstract: