[Species-specific differences in Rhodamine 6G accumulation of Candida isolates detected by flow cytometric analysis].
BACKGROUND
Fluorescent dye Rhodamine 6G (R6G) is a 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 various Candida species, only a few studies have been reported on the R6G accumulation among clinical isolates of Candida species. In this study, we compared R6G accumulation between six different Candida species.


METHODS
The intracellular accumulation of R6G and minimal inhibitory concentrations (MICs) of three triazole agents were investigated in 48 strains of six Candida species (14 C. albicans, 9 C. tropicalis, 8 C. glabrata, 8 C. krusei, 7 C. parapsilosis, and 2 C. haemulonii). R6G accumulation was measured by using flow cytometry and the geometric mean of the fluorescence intensity (GMF) was used to compare the accumulation between the Candida isolates.


RESULTS
The GMF values for the C. tropicalis, C. albicans, C. krusei, C. parapsilosis, and C. glabrata isolates were 167.3+/-18.5, 126.9+/-6.6, 88.5+/-18.5, 50.8+/-7.0, and 38.1+/-3.9, respectively. C. glabrata had a significantly lower mean GMF than all 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 with increased MICs to all three triazole agents had a reduced GMF.


CONCLUSIONS
This study found species-specific differences in R6G accumulation in Candida. In addition, the intracellular R6G accumulation can be used to investigate the drug efflux mechanism in azole-resistant Candida strains.
Department of Laboratory Medicine, Chonnam National University Medical School, Dong-gu, Gwangju, Korea.
Chang Jin
CJ
Moon
Jong Hee
JH
Shin
Da Woon
DW
Kim
Seung Jung
SJ
Kee
Soo Hyun
SH
Kim
Myung Geun
MG
Shin
Soon Pal
SP
Suh
Dong Wook
DW
Ryang
D000935:Antifungal Agents / Q000494:pharmacology; D001393:Azoles / Q000494:pharmacology; D002175:Candida / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D002177:Candidiasis / Q000188:drug therapy; D025141:Drug Resistance, Fungal; D005434:Flow Cytometry / Q000379:methods*; D015725:Fluconazole / Q000494:pharmacology; D005456:Fluorescent Dyes / Q000032:analysis*; D006801:Humans; D008826:Microbial Sensitivity Tests; D012235:Rhodamines / Q000032:analysis*; D013045:Species Specificity
D000935:Antifungal Agents; D001393:Azoles; D005456:Fluorescent Dyes; D012235:Rhodamines; C026188:rhodamine 6G; D015725:Fluconazole