Rapid flow cytometric susceptibility testing of candida species

ABSTRACT

The present study was performed to establish a standardized rapid antifungal susceptibility method using flow cytometry [FCM]. Also, to detect the antifungal susceptibility pattern of Candida species isolated in Ain Shams University Hospitals. For this purpose, 50 Candida isolates from different patients' specimens [urine, sputum, pus, blood and ascitic fluid] were identified to the species level using Microscan Walkaway 40. Their in vitro susceptibility to amphotericin B [AMB], fluconazole and ketoconazole was performed using 2 reference broth microdilution NCCLS M27-A and FCM. Membrane permeability changes of Candida caused by antifungal agents were measured by FCM using propidium iodide. The most common isolates were C. albicans [48%], C. Tropicalis [40%], and others C. parapsilosis, C. Lusitaniae, C. glabarata and C. Krusei [12%]. By both methods [M27-A and FCM], Candida species were 90% and 92% susceptible to AMB respectively; 80% and 4% susceptible to ketoconazole respectively and 84% and 88% susceptible to fluconazole respectively. On comparing results of both methods for antifungal susceptibility testing, it was found that by FCM, a 4 hrs incubation for azoles and 2 hrs incubation for AMB were aufficient to provide MICs comparable to the reference M27-A broth microdilution method developed by NCCLS. Subcommittee on antifungal susceptibility tests [correlation significance < 0.001]. Such work showed that FCM provides rapid and sensitive method for antifungal susceptibility of candida