Multicenter comparative evaluation of six commercial systems and the national committee for clinical laboratory standards m27-a broth microdilution method for fluconazole susceptibility testing of Candida species.
Fluconazole susceptibility among 800 clinical Candida isolates (60% C. albicans) and two control strains (C. krusei ATCC 6258 and C. parapsilosis ATCC 22019) was tested with the NCCLS M27-A method (gold standard) and six commercial products (Candifast, disk, Etest, Fungitest, Integral System Yeasts, and Sensititre YeastOne). Results were classified as susceptible, susceptible-dose dependent, or resistant using M27-A breakpoints or, for Fungitest, Integral System Yeasts, and Candifast, as susceptible, intermediate, or resistant, according to the manufacturers' instructions. Concordance with NCCLS M27-A results was analyzed with the chi(2) test. Intra- and interlaboratory reproducibility was also evaluated. NCCLS M27-A (90.1%), Etest (93.1%), Sensititre YeastOne (93.1%), disk (96.7%), Fungitest (92.6%), Integral System Yeasts (40.6%), and Candifast (6.0%) classified the indicated percentages of C. albicans isolates as susceptible. Among non-C. albicans strains, the percentages of susceptible isolates were as follows: NCCLS M27-A, 74.0%; Etest, 83.8%; Sensititre YeastOne, 64.1%; disk, 60.6%; Fungitest, 76.6%; Integral System Yeasts, 28.3%; and Candifast, 27.4%. All methods except Candifast and Integral System Yeasts showed good agreement with NCCLS M27-A results for both C albicans and non-C. albicans isolates. Intralaboratory reproducibility was excellent for NCCLS M27-A, Etest, Sensititre YeastOne, disk, and Fungitest (88 to 91%). Similar results emerged from the interlaboratory reproducibility evaluation. Our findings indicate that some commercial methods can be useful for fluconazole susceptibility testing of clinical Candida isolates. Those characterized by a lack of medium standardization and/or objective interpretative criteria should be avoided. Particular caution is necessary when testing is being done for clinical and epidemiological purposes.
Morace
G
G
Istituto di Microbiologia, Università degli Studi di Milano, Italy. giulia.morace@unimi.it
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D000935:Antifungal Agents / Q000494:pharmacology*; D002175:Candida / Q000187:drug effects*; D002177:Candidiasis / Q000382:microbiology; D015725:Fluconazole / Q000494:pharmacology*; D006801:Humans; D007753:Laboratories; D008826:Microbial Sensitivity Tests / Q000379:methods / Q000592:standards*; D011933:Reagent Kits, Diagnostic; D015203:Reproducibility of Results
D000935:Antifungal Agents; D011933:Reagent Kits, Diagnostic; D015725:Fluconazole