Establishment and application of a flow cytometry-based rapid drug susceptibility test for Candida species
Objective To establish a flow cytometry-based drug susceptibility test for the rapid de-tection of antifungal susceptibility or resistance of Candida isolates.Methods The gate selection and opti-mal experimental conditions of flow cytometry-based drug susceptibility test were determined by using Candi-da albicans strain ATCC90029 as the test strain and propidium iodide （ PI） as the fluorescent dye .The es-tablished flow cytometry-based drug susceptibility test was used to detect the susceptibility or resistance to fluconazole or voriconazole of 110 isolates belonging to Candida species, and the obtained results were com-pared with those by using typical M 27-A3 constant dilution method .Results The killed and viable Candida albicans ATCC90029 strains were clearly divided into two groups on the figure of SS /log （FL3） by regulating voltages.There was a high correlation between the results of susceptibility test and the proportions of killed and viable fungi in mixture （r=0.999）.The flow cytometry-based drug susceptibility test could provide the results within 30 min and its optimal concentration of fungal suspension , time of drug-fungus incubation , dyeing method and time were 1.0×106/ml, 3 h incubation and sodium deoxycholate-pretreated plus PI dye-ing for 5 min, respectively .The total coincident rates between the established test and the constant dilution method were 98.2%and 87.3%in the detection of drug susceptibility of 110 fungal isolates to fluconazole and voriconazole .Conclusion The flow cytometry-based drug susceptibility test shows advantages of rapidi-ty, accuracy and high sensitivity compared with the constant dilution method .It has a great potential for clin-ical application . 
 
Key words: 
Flow cytometry;  Drug susceptibility test ;  Candida;  Fluconazole ;  Voriconazole