title: Comparison of visual 24-hour and spectrophotometric 48-hour MICs to CLSI reference microdilution MICs of fluconazole, itraconazole, posaconazole, and voriconazole for Candida spp.: a collaborative study.
abstract: A multicenter (six-center) study evaluated the performance (interlaboratory reproducibility, compatibility with reference methods, and categorical agreement) of 24-h visual and 48-h spectrophotometric MICs. MICs of fluconazole, itraconazole, voriconazole, and posaconazole were compared to reference 48-h microdilution broth visual MICs (CLSI [formerly NCCLS] M27-A2 document) for 71 isolates of Candida spp. that included 10 fluconazole-resistant strains. Twenty readings (5%) were reported as showing no growth at 24 h, mostly for Candida dubliniensis and from a single center. The overall interlaboratory agreement of 24-h visual readings and 48-h spectrophotometric MICs, as well their compatibility with reference values, were excellent with the four triazoles for most of the species (93 to 99%, within 3 dilutions). The categorical agreement between the investigational reading conditions and reference values was good with fluconazole and voriconazole (93 to 97%) but lower with itraconazole (86 to 88%), due primarily to minor errors. There were only 0 to 3% very major errors with these three triazoles; the number of substantial errors (more than three dilutions) was also low (<2%) with posaconazole. These data suggest that the performance of both investigational MIC readings gives results similar to those of reference MICs. Since spectrophotometric MICs are more objective and the 24-h time period would shorten the MIC determination of azoles, the description of either of these two reading conditions in the M27-A2 document should be considered by the CLSI subcommittee in addition to or instead of the longer, less practical, and more subjective 48-h visual MIC reading.
authors.affiliation: VCU Medical Center, Richmond, VA 23298-0049, USA. avingrof@hsc.vcu.edu
authors.forename: A
authors.initials: A
authors.lastname: Espinel-Ingroff
authors.forename: F
authors.initials: F
authors.lastname: Barchiesi
authors.forename: M
authors.initials: M
authors.lastname: Cuenca-Estrella
authors.forename: A
authors.initials: A
authors.lastname: Fothergill
authors.forename: M A
authors.initials: MA
authors.lastname: Pfaller
authors.forename: M
authors.initials: M
authors.lastname: Rinaldi
authors.forename: J L
authors.initials: JL
authors.lastname: Rodriguez-Tudela
authors.forename: P E
authors.initials: PE
authors.lastname: Verweij
mesh_terms: D000935:Antifungal Agents / Q000494:pharmacology*; D002175:Candida / Q000145:classification / Q000187:drug effects*; D002177:Candidiasis / Q000382:microbiology; D025141:Drug Resistance, Fungal; D015725:Fluconazole / Q000494:pharmacology*; D006801:Humans; D017964:Itraconazole / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests / Q000379:methods / Q000592:standards; D011743:Pyrimidines / Q000494:pharmacology*; D012015:Reference Standards; D015203:Reproducibility of Results; D013053:Spectrophotometry; D014230:Triazoles / Q000494:pharmacology*; D065819:Voriconazole
chemical_list: D000935:Antifungal Agents; D011743:Pyrimidines; D014230:Triazoles; D017964:Itraconazole; C101425:posaconazole; D015725:Fluconazole; D065819:Voriconazole