Poster (Scientific congresses and symposiums)
Multicentre validation of a EUCAST method for the antifungal susceptibility testing of microconidia-forming dermatophytes
Arendrup, Maiken; Jorgensen, Karin; Guinea, Jesus et al.
202030th ECCMID
 

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Keywords :
Eucast; suceptibility testing
Abstract :
[en] Background: Terbinafine resistance is increasingly reported in Trichophyton rubrum and Trichophyton interdigitale rendering susceptibility testing important particularly in non-responding cases. We performed a multicentre evaluation of a recently proposed modified EUCAST method implementing medium supplemented with chloramphenicol and cycloheximide (CC) to avoid contamination. Materials/methods: A blinded panel of wild-type and squalene epoxidase (SQLE) target gene mutant T. rubrum and T. interdigitale strains were distributed to 10 European laboratories. Susceptibility to terbinafine, itraconazole, voriconazole and amorolfine) were performed according to the E.Def 9.3.1 method with and without addition of chloramphenicol and cycloheximide (final concentrations 50 mg/L and 300 mg/L, respectively). Plates were incubated at 25 °C (one laboratory used 30 °C) for 5-7 days until sufficient growth. MICs were determined visually (ignoring trailing growth for itraconazole) and spectrophotometrically with 90% and 50% endpoints yielding a total of 7,829 MICs. A. flavus ATCC 204304 and A. flavus CNM-CM1813 were included as controls. Results: 100%/96% (voriconazole) and 84%/84% (itraconazole) MIC determinations fell within the QC ranges for the two QC strains, respectively, and 96%/92% terbinafine MICs fell in a 0.25-1 mg/L 3 two-fold-dilution range suggesting a high interlaboratory reproducibility. Across the six methods, the number of terbinafine MEs varied from 2 (2.6%) to 5 (6.6%) for T. rubrum and between 0 and 2 (2.0%) for T. interdigitale (lowest for the CC-method (2.6%-4.4%/ 0-1% for T. rubrum/T. interdigitale). The difference between the modes for the wt and mutant population were ≥7 two-fold-dilutions in all cases (Table). If excluding a I121M/V237I T. rubrum mutant, and two mixed T. interdigitale strains, the number of VMEs were CC visual: T. rubrum: 1/77 (1.3%), CC spec-90%: 3/68 (4.4%) and CC spec-50%: 1/76 (1.3%), and none for T. interdigitale. The activity of voriconazole, itraconazole and amorolfine were quite uniform against T. rubrum and T. interdigitale, but unacceptably wide MIC ranges were found for the visual and spec-90% inhibition methods for itraconazole (data not shown). Conclusions: Although none of the laboratories perform dermatophyte testing at a regular basis an acceptable interlaboratory agreement and good separation between SQLE wt and mutants were found, suggesting a robust performance of the proposed method.
Disciplines :
Microbiology
Author, co-author :
Arendrup, Maiken;  Statens Serum Institut, Copenhagen, Denmark > Unit for Mycology
Jorgensen, Karin;  Statens Serum Institut, Copenhagen, Denmark > Unit for Mycology
Guinea, Jesus;  Hospital General Universitario Gregorio Marañón, Madrid, Spain > Clinical Microbiology and Infectious Diseases
Lagrou, Katrien;  KULeuven > Clinical microbiology and NRC Mycoses
Chryssanthou, Erja;  Karolinska University Hospital, Stockholm, Sweden > Department of Clinical Microbiology
Hayette, Marie-Pierre ;  Université de Liège - ULiège > Département des sciences biomédicales et précliniques > Bactériologie, mycologie, parasitologie, virologie
Barchiesi, Francesco;  Università Politecnica delle Marche, Ancona, Italy > Dipartimento di Scienze Biomediche e Sanità Pubblica
Lass Flörl, Cornelia;  Medical University of Innsbruck, Innsbruck, Austria > Institute of Hygiene and Medical Microbiology
Hamal, Petr;  University Hospital, Olomouc, Czech Republic > Department of Microbiology
Dannaoui, Eric;  Georges Pompidou European Hospital, University of Paris, France > Parasitology-Mycology Unit, Microbiology Department
Chowdhary, Anuradha;  Vallabhbhai Patel Chest Institute, University of Delhi, Delhi, India > Department of Medical Mycology
Meletiadis, Joseph;  Attikon University Hospital, Medical School, National and Kapodistrian University of Athens > Clinical Microbiology Laboratory
Language :
English
Title :
Multicentre validation of a EUCAST method for the antifungal susceptibility testing of microconidia-forming dermatophytes
Alternative titles :
[fr] Evaluation multicentrique d'une méthode EUCAST pour tester la sensibilité antifongique des dermatophytes produisant des spores
Publication date :
April 2020
Number of pages :
Mini-oral ePoster session
Event name :
30th ECCMID
Event organizer :
ESCMID
Event place :
Paris, France
Event date :
du 18 au 21 avril 2020
Audience :
International
Available on ORBi :
since 27 January 2020

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