Multicenter evaluation of a broth macrodilution antifungal susceptibility test for yeasts

• DOI: 10.1128/aac.37.1.39
• Publication Date: 2012-06-28T00:05:50Z
• Authors: R A Fromtling; J N Galgiani; M A Pfaller; A Espinel-Ingroff; K F Bartizal; M S Bartlett; B A Body; C Frey; G Hall; G D Roberts
• Keywords: Candida glabrata; Flucytosine; Candida parapsilosis; Serial dilution

Thirteen laboratories collaborated to optimize interlaboratory agreement of results a broth macrodilution procedure for testing three classes antifungal drugs against pathogenic yeasts. The activities amphotericin B, flucytosine, and ketoconazole were tested 100 coded isolates Candida albicans, tropicalis, parapsilosis, lusitaniae, Torulopsis (Candida) glabrata, Cryptococcus neoformans. Two starting yeast inoculum sizes (5 x 10(4) 2.5 10(3) cells per ml) compared, readings taken after 24 48 h incubation. All other test conditions standardized. resultant turbidities in all tubes estimated visually on scale from 0 4+ turbidity, MIC-0, MIC-1, MIC-2 defined as the lowest drug concentrations that reduced growth 0, 1+, or 2+ respectively. For among varied between 57 87% different inocula, times incubation, end point criteria. Agreement was maximized (85%) when lower incubated 2 days MICs 1+ turbidity less. variations produced much smaller differences agreement. ketoconazole, poorer by However, endpoints distinguished T. glabrata resistant compared with species. Overall, studies indicated obtained second day reading result greatest In combination data previous multicenter (National Committee Clinical Laboratory Standards, Antifungal Susceptibility Testing: Report, Vol. 5, No. 17, 1988; M. A. Pfaller, L. Burmeister, S. Bartlett, G. Rinaldi, J. Clin. Microbiol. 26:1437-1441, N. Galgiani, B.A. Body, Espinel-Ingroff, R.A. Fromtling, G.S. Hall, C.E. Hughes, F. C. Odds, SUgar, 34:1648-1654, 1990), these findings will be used National Standards develop standardized method vitro susceptibility