A-036. Flow Cytometric Analysis of Rhodamine 6G Accumulation in Different Candida Species

S-H. Kim1, C-J. Moon1, J-H. Shin2, M-G. Shin1, S-P. Suh3, D-W. Ryang3;
1Chonnam Natl. Univ. Hwasun Hosp., Hwasun-gun, REPUBLIC OF KOREA, 2Chonnam Natl. Univ. Hwasun Hosp., Gwangju, REPUBLIC OF KOREA, 3Chonnam Natl. Univ. Hosp., Gwangju, REPUBLIC OF KOREA.

Background: The fluorescent dye Rhodamine 6G (R6G) is the substrate of multidrug resistance pumps and its accumulation is reduced in some azole-resistant Candida isolates with the upregulation of multidrug efflux transporter genes. Despite reports on species-specific differences in azole susceptibility in different Candida species, few studies have compared R6G accumulation among clinical isolates of different Candida species. Methods: The intracellular accumulation of R6G was investigated in 48 strains of six different Candida species (14 C. albicans, 9 C. tropicalis, 8 C. glabrata, 8 C. krusei, 7 C. parapsilosis, and 2 C. haemulonii). The minimal inhibitory concentrations (MICs) of three triazole agents (fluconazole, itraconazole, and voriconazole) were determined using the broth microdilution method of the Clinical and Laboratory Standards Institute (CLSI). R6G accumulation was measured using flow cytometry in a FACScan flow cytometer (Becton Dickinson Biosciences, San Jose, USA) and the geometric mean of the fluorescence intensity (GMF) was used to compare the Candida isolates. Results: The mean GMF for the C. tropicalis, C. albicans, C. krusei, C. parapsilosis, and C. glabrata isolates was 167.3±3.9, 126.9±6.6, 88.5±18.5, 50.8±7.0, and 38.1±18.5, respectively. C. glabrata had a significantly lower mean GMF than all of the other Candida species (P<0.05). While some Candida strains with trailing growth phenomenon and increased fluconazole MIC did not have a reduced GMF, three Candida strains (two C. glabrata and one C. parapsilosis isolate) with increased MICs to all three triazole agents had a reduced GMF, which suggested multidrug efflux. Conclusions: This study found species-specific differences in R6G accumulation in Candida. C. glabrata isolates tended to accumulate less R6G than other Candida species. In addition, the intracellular R6G accumulation can be used to investigate the drug efflux mechanism in azole-resistant Candida strains.