Fluconazole susceptibility testing of Candida species by flow cytometry.
OBJECTIVE
Currently, antifungal drug susceptibility testing is labor-intensive, limited by delays in obtaining results and high costs. The purpose of this study was to determine the usefulness of flow cytometry (FCM) antifungal drug susceptibility testing as a routine laboratory procedure.


METHODS
A total of 24 clinical isolates of Candida spp. and reference strains were tested for susceptibility to fluconazole by FCM using propidium iodide (PI) as an indicator of viability. The minimum inhibitory concentration (MIC) was defined as the lowest concentration of fluconazole that resulted in an increase of 30% in mean channel fluorescence (MCF), compared to the growth control. FCM results were compared with MIC results as determined by the Clinical and Laboratory Standards Institute (CLSI) method.


RESULTS
An 8h incubation was sufficient for determination of the MICs. The results by FCM at 8h and the NCCLS methods at 24h showed 87.5% agreement to within two drug dilutions. However, the FCM method is labor-intensive in proportion to the larger number of samples. For Candida lusitaniae, MICs by the FCM method showed poor correlation with the CLSI method.


CONCLUSIONS
Further evaluation is necessary to assess the usefulness of FCM as a technique for routine antifungal MIC testing in the clinical laboratory.
Joung
Young Hee
YH
Department of Laboratory Medicine, Chung-Ang University College of Medicine, 65-207, 3-Ka Hangang-Ro, Yongsan-Ku, Seoul 140-757, South Korea.
Kim
Hye Ryoun
HR
Lee
Mi Kyung
MK
Park
Ae Ja
AJ
D000935:Antifungal Agents / Q000494:pharmacology*; D002175:Candida / Q000145:classification / Q000187:drug effects*; D002177:Candidiasis / Q000382:microbiology; D005434:Flow Cytometry / Q000379:methods*; D015725:Fluconazole / Q000494:pharmacology*; D006801:Humans; D008826:Microbial Sensitivity Tests; D011419:Propidium; D015203:Reproducibility of Results; D013997:Time Factors
D000935:Antifungal Agents; D011419:Propidium; D015725:Fluconazole