QUALITY-CONTROL GUIDELINES FOR NATIONAL COMMITTEE FOR CLINICAL LABORATORY STANDARDS RECOMMENDED BROTH MACRODILUTION TESTING OF AMPHOTERICIN-B, FLUCONAZOLE, AND FLUCYTOSINE

Amphotericin B, fluconazole, and flucytosine (5FC) were tested in a mu ltilaboratory study to establish quality control (QC) guidelines far y east antifungal susceptibility testing. Ten candidate QC strains were tested in accordance with National Committee for Clinical Laboratory S tandards M27-P guidelines against the three antifungal agents in each of six laboratories. Each laboratory was assigned a unique lot of RPMI 1640 broth medium as well as a lot of RPMI 1640 common to all of the laboratories. The candidate QC strains were tested 20 times each again st the three antifungal agents in bath unique and common lots of RPMI 1640. A minimum of 220 MICs per drug per organism were generated durin g the study. Overall, 95% of the MICs of amphotericin B, fluconazole, and 5FC fell within the desired 3 log(2)-dilution range (mode +/- 1 lo g(2) dilution), Excellent performance with all three drugs was observe d for Candida parapsilosis ATCC 22019 and C. krusei ATCC 6258. With th ese strains, an-scale 3 log(2)-dilution ranges encompassing 96 to 99% of the MICs of all three drugs were established. These two strains are recommended for QC testing of amphotericin B, fluconazole, and 5FC. R eference ranges were also established for an additional four strains f or use in method development and for training. Four strains failed to perform adequately for recommendation as either QC or reference strain s.