Fluconazole Susceptibility Testing And Partial Promoter Analysis Of ERG11 In Candida Albicans

Objective:To compare the differences of the activity of fluconazole against the yeast form and the hyphal form of Candida albicam and the base sequences of partial ERG11 promoter (-440~-1) between the two forms, and to investigate the correlation between the mutations of ERG11 promoter and C. albicam resistance to fluconazole. Materials and methods:Refering to M27-A and M38-P microdilution metholds recommended by National Committee for Clinical Laboratoty Standards (NCCLS), the minimum inhibitory concentrations (MICs) of the yeast form and the hyphal form of 16 isolates of C. albicam from a single strain were determined, and the differences of the MICs of the two forms were compared. The genomic DNA of the yeast form and the hyphal form of 4 isolates in this series of C. albicam (Two were fluconazole-susceptible, one was -susceptible dose dependent, and one was -resistant) were extracted. A pair of primers was designed according to the sequences of ERG11 and its promoter. The partial ERG11 promoter sequence was amplified with polymerase chain reaction (PCR). After PCR amplication, the products were sequenced from both directions.Results:The MICs of the yeast form of C. albicam were different from those of the hyphal form. The activity of fluconazole against the hyphal form of C. albicam was higher than that agaisnt the yeast form. No base difference was found in the partial ERG11 promoter between the two forms of C. albicam. Base differences of the partialERG11 promoter at position -365, -353, -328, -310, -308, -299, -295, -293, -292, -290 and -289, and a single base deletion (-284 delT) were found between the alleles in the diploid genome in fluconazole-sensitive isolates. No heterogeneities were observed in fluconazole-sensitive dose dependent isolates and -resistant.Conclusion:The activity of fluconazole against the yeast form and the hyphal form of C. albicans are different. There is no sequence difference from position -440 to -1 in ERG11 promoter between the yeast form and the hyphal form of C. albicans. Mutations of ERG11 promoter maybe relates to C. albicans resistance to fluconazole.