title: Echinocandin susceptibility testing of Candida species: comparison of EUCAST EDef 7.1, CLSI M27-A3, Etest, disk diffusion, and agar dilution methods with RPMI and isosensitest media.
abstract: This study compared nine susceptibility testing methods and 12 endpoints for anidulafungin, caspofungin, and micafungin with the same collection of blinded FKS hot spot mutant (n = 29) and wild-type isolates (n = 94). The susceptibility tests included EUCAST Edef 7.1, agar dilution, Etest, and disk diffusion with RPMI-1640 plus 2% glucose (2G) and IsoSensitest-2G media and CLSI M27A-3. Microdilution plates were read after 24 and 48 h. The following test parameters were evaluated: fks hot spot mutants overlapping the wild-type distribution, distance between the two populations, number of very major errors (VMEs; fks mutants misclassified as susceptible), and major errors (MEs; wild-type isolates classified as resistant) using a wild-type-upper-limit value (WT-UL) (two twofold-dilutions higher than the MIC(50)) as the susceptibility breakpoint. The methods with the lowest number of errors (given as VMEs/MEs) across the three echinocandins were CLSI (12%/1%), agar dilution with RPMI-2G medium (14%/0%), and Etest with RPMI-2G medium (8%/3%). The fewest errors overall were observed for anidulafungin (4%/1% for EUCAST, 4%/3% for CLSI, and 3%/9% for Etest with RPMI-2G). For micafungin, VME rates of 10 to 71% were observed. For caspofungin, agar dilution with either medium was superior (VMEs/MEs of 0%/1%), while CLSI, EUCAST with IsoSensitest-2G medium, and Etest were less optimal (VMEs of 7%, 10%, and 10%, respectively). Applying the CLSI breakpoint (S <OR= 2 microg/ml) for CLSI results, 89.2% fks hot spot mutants were classified as anidulafungin susceptible, 60.7% as caspofungin susceptible, and 92.9% as micafungin susceptible. In conclusion, no test was perfect, but anidulafungin susceptibility testing using the WT-UL to define susceptibility reliably identified fks hot spot mutants.
authors.affiliation: Unit of Mycology and Parasitology (43/117), Statens Serum Institut, Artillerivej 5, DK-2300 Copenhagen S, Denmark. mad@ssi.dk
authors.forename: Maiken Cavling
authors.initials: MC
authors.lastname: Arendrup
authors.forename: Guillermo
authors.initials: G
authors.lastname: Garcia-Effron
authors.forename: Cornelia
authors.initials: C
authors.lastname: Lass-Flörl
authors.forename: Alicia Gomez
authors.initials: AG
authors.lastname: Lopez
authors.forename: Juan-Luis
authors.initials: JL
authors.lastname: Rodriguez-Tudela
authors.forename: Manuel
authors.initials: M
authors.lastname: Cuenca-Estrella
authors.forename: David S
authors.initials: DS
authors.lastname: Perlin
mesh_terms: D000077612:Anidulafungin; D000935:Antifungal Agents / Q000494:pharmacology*; D002175:Candida / Q000187:drug effects* / Q000235:genetics; D002177:Candidiasis / Q000382:microbiology; D000077336:Caspofungin; D003470:Culture Media; D054714:Echinocandins / Q000494:pharmacology*; D007201:Indicator Dilution Techniques; D055666:Lipopeptides / Q000494:pharmacology; D000077551:Micafungin; D008826:Microbial Sensitivity Tests / Q000379:methods* / Q000592:standards; D012015:Reference Standards
chemical_list: D000935:Antifungal Agents; D003470:Culture Media; D054714:Echinocandins; D055666:Lipopeptides; D000077612:Anidulafungin; D000077336:Caspofungin; D000077551:Micafungin