EVALUATION OF A FLOW CYTOFLUOROMETRIC METHOD FOR RAPID-DETERMINATION OF AMPHOTERICIN-B SUSCEPTIBILITY OF YEAST ISOLATES

A rapid-flow cytofluorometric susceptibility test for in vitro amphote ricin B testing of yeasts was evaluated and compared to the National C ommittee for Clinical Laboratory Standards (NCCLS) M27-T reference bro th macrodilution method, The flow cytofluorometric method is based on the detection of decreased green fluorescence intensity of cells stain ed with DiOC(5)(3), a membrane potential-sensitive cationic dye, after drug treatment, Testing was performed on 134 clinical isolates (Candi da spp, and Torulopsis glabrata). From the dose-response curve obtaine d for each isolate, three endpoints were calculated by computer analys is (the concentrations at which the fluorescence intensity was reduced by 50, 80, and 90%, i.e., 50% inhibitory concentration [IC50], IC80, and IC90, respectively), A regression analysis correlating these endpo ints with the M27-T MICs showed that the best agreement was obtained w ith IC80. The flow cytofluorometric method showed good reproducibility with control strains, These initial results suggest that the flow cyt ofluorometric method is a valid alternative to the NCCLS reference met hod.