Establishment And Application Of Flow Cytometric-based Rapid Drug Susceptibility Test Of Candida Species

Objective To develop a rapid flow cytometry-based drug susceptibility test to detect susceptibility or resistance to antifungal drugs in clinical isolates of Candida species.Methods The gate selection and optimal experimental conditions of flow cytometry-based drug susceptibility test were determined using Candida albicans strain ATCC90029as the tested strain and propidium iodide (IP) as the fluorescent dye. The established flow cytometry-based drug susceptibility test was used to detect the susceptibility or resistance to fluconazole or voriconazole of110isolates belonging to Candida species, and the obtained result was compared to that from typical M27-A3constant dilution method.Results The death or living Candida albicans strain ATCC90029could be divided into two clearly separated groups in SS/log (FL3) gate in flow cytometer by regulating voltages and the detection results of displayed a high dependablity with the numbers of dead and living fungi in mixture with different proportions (r=0.999). The flow cytometry-based drug susceptibility test could provide the results within30min. The optimal concentration of fungal suspension, time of drug-fungus incubation, dyeing method and time in the flow cytometry-based drug susceptibility test were1.0×106/ml,3-h incubation and sodium deoxycholate-pretreated plus PI dyeing for5min, respectively. The total coincident rates of results from the flow cytometry-based drug susceptibility test and constant dilution method in fluconazole and voriconazole to inhibit the110fungal isolates were98.2%and87.3%, respectively. Conclusion The flow cytometry-based drug susceptibility test established in this study is rapid, accurate and sensitive method to detect the susceptibility or resistance of fungi compared to the typical constant dilution method, which has a potential for clinical application.