25S rDNA genotype and antifungal susceptibility of vaginal Candida albicans

Abstract

To investigate 25S rDNA genotype distribution of vaginal Candida albicans and its relationship with antifungal susceptibility. A total of 954 isolates of Candida albicans were subjected to genotype analysis according to the presence and the size of transposable group Ⅰ intron in 25S rDNA with PCR; 156 isolates were enrolled to detect their antifungal susceptibility of 5 antifungal agents with the M27-A3 broth microdilution method. Totally 876 isolates were determined to be intronless genotype A(91.8%, 876/954); 58(6.1%, 58/954)and 20 isolates(2.1%, 20/954)were introncontaining genotype B and genotype C, respectively. The minimal inhibitory concentrations(MIC)of itraconazole and fluconazole against the intron-containing group were significantly higher than those of the intronless group(0.25 versus 0.125 μg/ml, P<0.05; 0.25 versus 0.125 μg/ml, P<0.01), whereas the MIC of nystatin against the intron-containing group was lower than that of the intronless group(4 versus 8 μg/ml, P< 0.01). The resistance rate of Candida albicans to itraconazole of the intron-containing group was significantly higher than that of the intronless group[24%(19/78)versus 3%(2/78), P<0.01]. Cross-resistance analysis revealed 5 of the 21(24%)itraconazole resistant isolates were cross-resistant to fluconazole , and 5 of the 6(5/6)fluconazole-resistant strains were cross-resistant to itraconazole. Besides, all the five strains simultaneously resistant to itraconazole and fluconazole belonged to the intron-containing group. The presence of the transposable group Ⅰ intron in 25S rDNA of vaginal Candida albicans might be important in affecting itraconazole, fluconazole and nystatin susceptibility.