Objective: To determine if changes in the levels of expression of ERG11, CDR1 and CDR2 genes could be associated with resistance phenotype in clinical isolates of Candida glabrata (C. glabrata).
Methods: We used quantitative RT-PCR analysis to evaluate the expression of the ERG11, CDR1 and CDR2 genes in clinical isolates including 9 fluconazole-resistant, 9 fluconazole-susceptible dose dependent (S-DD) and 10 fluconazole-sensitive C. glabrata isolates.
Results: In the fluconazole-resistant isolates, the S-DD isolates and the fluconazole-sensitive isolates, the levels of expression of ERG11 gene were 121.4 +/- 96.8, 102.9 +/- 78.8, 51.2 +/- 20.7, respectively; the levels of expression of CDR1 gene were 3.1 +/- 1.4, 1.9 +/- 0.7, 1.1 +/- 0.4, respectively; the levels of expression of CDR2 gene were 3.7 +/- 2.2, 3.4 +/- 2.4, 1.9 +/- 0.9, respectively. Quantitative RT-PCR analyses revealed that the fluconazole-resistant isolates expressed ERG11 at higher levels than fluconazole-sensitive isolates (P = 0.041). CDR1 expression was significantly higher in the fluconazole-resistant isolates as compared with that in the fluconazole-sensitive isolates (P < 0.001) and the expression was also significantly higher in the S-DD isolates as compared with that in the fluconazole-sensitive isolates (P = 0.009). CDR2 upregulation was observed in the fluconazole-resistant isolates as compared with the susceptible isolates (P = 0.018). With the decrease of susceptibility to fluconazole, the levels of expression of ERG11, CDR1 and CDR2 genes in the isolates appeared to be increased.
Conclusions: These results provide evidence that the overexpression of ERG11, CDR1 and CDR2 genes is associated with the increase of fluconazole resistance in clinical isolates of C. glabrata. ERG11, CDR1 and CDR2 upregulation is a major molecular mechanism of fluconazole resistance in clinical isolates of C. glabrata.