Antifungal susceptibility testing of fluconazole by flow cytometry correlates with clinical outcome

Susceptibility testing of fungi by flow cytometry (also called fluorescence-activated cell sorting [FACS]) using vital staining with FUN-1 showed a good correlation with the standard M27-A procedure for assessing MICs. In this study we determined MICs for blood culture isolates from patients with candidemia by NCCLS M27-A and FAGS methods and correlated the clinical outcome of these patients with in vitro antifungal resistance test results, A total of 24 patients with candidemia for whom one or more blood cultures were positive for a Candida sp. were included. Susceptibility testing was performed by NCCLS M27-A and FACS methods. The correlation of MICs (NCCLS M27-A and FAGS) and clinical outcome was calculated. In 83% of the cases, the MICs of fluconazole determined by FAGS were within 1 dilution of the MICs determined bg the NCCLS M27-A method. For proposed susceptibility breakpoints, there was 100% agreement between the M27-A and FAGS methods. In the FAGS assay, a fluconazole MIC of <1 mug/ml was associated with cure (P < 0.001) whereas an MIC of greater than or equal to1 mug/ml was associated with death (P < 0.001), The M27-A-derived fluconazole MICs did not correlate with outcome (P = 1 and P = 0.133).