Susceptibility tests of oropharyngeal Candida albicans from egyptian patients to fluconazole determined by three methods

Candida albicans frequently cause oropharyngeal candidiasis in immunocompromised patients. As some of these isolates show resistance against azoles, the clinician is wary of initiating therapy with fluconazole (FZ) until a final susceptibility report is generated. We aimed to evaluate the efficacy of rapid flow cytometry (FCM) and disc diffusion (DD) methods in comparison to reference microdilution (MD) of Clinical and Laboratory Standards Institute (CLSI) method for FZ. Thirty seven Candida albicans isolates were tested by the three methods. By both MD and FCM, 26/37 (70.3%) were sensitive with minimal inhibitory concentration (MIC) ≤ 8μg/ml, 5/37 (13.5%) were susceptible dose dependant (S-DD) with MIC 16-32 μg/ml and 6/37 (16.2%) were resistant with MIC ≥64μg/ml. More than 92% of isolates susceptible to FZ by the MD were susceptible by the DD methods with good agreement (81.08%, P = 0.000). However, 4/5 isolates diagnosed as S-DD by MD were resistant by DD. Interestingly, the MIC by FCM at 4 h showed excellent agreement (95.59%, P = 0.000) to that obtained by MD method at 24 h. Overall, FCM antifungal susceptibility testing provided rapid, reproducible results that are valuable alternative to MD. The DD test is recommended as a simple and reliable screening test for the detection of susceptible Candida albicans isolates to FZ.