Detection of ERG11 gene mutation in coding and non-coding regions of clinical Candida glabrata (Nakaseomyces glabratus) isolates from Pakistan

Azoles inhibit the cytochrome P450-dependent enzyme lanosterol 14α-demethylase (CYP51) that is encoded by the ERG11 gene. Azole resistance in Candida species arises through different mechanisms, like mutations in the ERG11 gene, ERG11 overexpression, CDR1,2 (Candida drug resistance) overexpression that actively efflux azole drugs, reducing their intracellular concentration and therapeutic effectiveness, and biofilm formation. We sequenced the ERG11 gene to determine mutations in the coding and non-coding regions of ERG11 in clinical isolates of Candida glabrata (Nakaseomyces glabratus) from Pakistan. Eight C. glabrata (N. glabratus) strains from our fungal strain bank (five fluconazole-resistant and three susceptible dose-dependent) were revived and used. The ERG11 gene was amplified by PCR, sequenced using the Sanger methodology and analysed using bioinformatic tools. We identified a change in nucleotide at c. -66 T/G upstream of the start codon ATG in the promoter region of the ERG11 gene in fluconazole-resistant C. glabrata (N. glabratus). Within the downstream (coding region), where numbering begins at the ATG start codon as position +1, two novel synonymous mutations at positions T300C and T834C and previously reported synonymous mutations T768C, A1023G, T1557A and A1581G were also observed. This is the first study evaluating ERG11 mutations in C. glabrata (N. glabratus) from Pakistan. The clinical significance of such uncommon ERG11 gene mutations, such as c. -66 T/G, should be explored further through correlation with treatment outcome data.