Article open access publication

Multicentre validation of 4-well azole agar plates as a screening method for detection of clinically relevant azole-resistant Aspergillus fumigatus.

Journal of Antimicrobial Chemotherapy, Oxford University Press (OUP), ISSN 1460-2091

Volume 72, 12, 2017

DOI:10.1093/jac/dkx319, Dimensions: pub.1091034815, PMID: 29029256,



  1. (1) State Serum Institute, grid.6203.7
  2. (2) University of Copenhagen, grid.5254.6, KU
  3. (3) Canisius-Wilhelmina Ziekenhuis, grid.413327.0
  4. (4) Radboud University Nijmegen Medical Centre, grid.10417.33
  5. (5) Erasmus University Medical Center, grid.5645.2
  6. (6) KU Leuven, grid.5596.f
  7. (7) Universitair Ziekenhuis Leuven, grid.410569.f
  8. (8) National and Kapodistrian University of Athens, grid.5216.0









Objectives: Azole-resistant Aspergillus fumigatus is emerging worldwide. Reference susceptibility testing methods are technically demanding and no validated commercial susceptibility tests for moulds currently exist. In this multicentre study a 4-well azole-containing screening agar method was evaluated using clinically relevant isolates. Methods: Forty WT and 39 cyp51A mutant A. fumigatus [G54 (n = 10), M220 (n = 10), TR34/L98H (n = 9) and TR46/Y121F/T289A (n = 10)] were tested individually and as simulated mixed samples (sampling 4 WT and 1 mutant colonies). EUCAST MICs were determined following E.Def 9.3. In-house and commercial 4-well plates containing agars supplemented with 4 mg/L itraconazole, 1 mg/L voriconazole, 0.5 mg/L posaconazole and no antifungal, respectively, were evaluated. Growth was scored (0-3) by two independent observers in three laboratories. Inter-plate, inter-observer, essential and categorical agreement, sensitivity and specificity were calculated. Results: CYP51A genotype and antifungal compound-specific MICs and growth patterns were documented. The inter-observer agreement was excellent with 86%-99% identical scores (range 80%-100%) for both plates. The qualitative agreement (no growth versus growth) was excellent (median 95%-100%, range 87%-100%, overall). The overall sensitivity and specificity for the 4-well plate (no growth versus growth) was 99% (range 97%-100%) and 99% (95%-100%), respectively. The sensitivity for simulated WT/mutant specimens was 94% (range 83%-100%) for the WT-TR34/L98H combination, but 100% for the WT/G54W combination. The performance remained unchanged using only itraconazole- and voriconazole-containing agars, but was lower for the other combinations. Conclusions: Implementation of the 4-well screening plate in routine laboratories will allow easy and reliable detection of the most common azole-resistant A. fumigatus.

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Field Citation Ratio (FCR): 11.79

Relative Citation ratio (RCR): 2.73

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