ERG11 mutations and expression of resistance genes in fluconazole-resistant Candida albicans isolates

Abstract

Azole resistance in the pathogenic yeast Candida albicans poses significant challenges for its antibiotic treatment. The conformational change of the target enzyme 14 alpha-demethylase (Erg11p) due to ERG11 gene mutations is one of the mechanisms resulting in the azole resistance. ERG11 of 23 isolates (8 susceptible and 15 resistant) and 6 standard strains of Candida albicans were amplified and sequenced. Nineteen missense mutations were detected. Two mutations, G487T (A114S) and T916C (Y257H), coexisted exclusively in 14 fluconazole-resistant isolates. To identify the resistance mechanisms in the isolates with G487T and T916C mutations, we compared the expression of 5 resistance-related genes in the 14 azole-resistant isolates with those in the susceptible type strain ATCC 10231, Saccharomyces cerevisiae AD/CDR1 and AD/CDR2. The tested values of mRNA transcription of CDR1 and CDR2 were higher than that of control strain, while the semi-quantified Cdr1p values were not higher in all of the 14 resistant isolates. And the data analyzed with t test suggest that both of the differences are significant (P < 0.0005) when the resistant isolates are considered as a whole. Cdr2p was up-regulated in 5 isolates, and down-regulated or even undetectable in the remaining 9 isolates. The transcription of ERG11, MDR1, and FLU1 varied in these isolates. These data suggested that overexpression of the five genes might not be the reason of resistance in the 14 isolates with G487T and T916C, especially in the 5 isolates (GZ09, GZ15, GZ16, GZ58, and 4263) in which neither translation of Cdr1p/Cdr2p nor transcription of ERG11, MDR1, or FLU1 was detected up-regulated. The results suggest that Erg11p conformational change due to the point mutations is most likely responsible for the azole resistance in these isolates.

A CTG Clade Candida Yeast Genetically Engineered for the Genotype-Phenotype Characterization of Azole Antifungal Resistance in Human-Pathogenic Yeasts

“…Surprisingly, in spite of using the same clonal genetic background of strain E11ura3Δ5=, RT-qPCR assays showed variations in amounts of ERG11 mRNA detected, possibly due to different mRNA half-lives within the cell or to slight variations of UPC2 expression, the transcription factor that regulates ERG11 (29). However, the variations detected, less than 3-fold, are not expected to have a significant effect on fluconazole MIC or to be correlated to a specific resistance pattern, as previously reported in several studies with C. albicans (30,31,32,33). Furthermore, both the Y132H and G464S CaERG11 alleles were expressed at the same level in C. lusitaniae E11ura3Δ5=, indicating that the lack of phenotype with Y132H only was probably not derived from a decreased expression level of CaERG11.…”

Evolution of Susceptibility of Strains of Candida Fluconazole and Determination of Antibiotic Resistance Genes

“…of them, 2 mutations, G487T (A114S) and T916C (Y257H), coexisted solely in 14 fluconazole -resistant separate. To know the resisting device in the separate with G487T and T916C mutations, we contrast the explanation of 5 resisting -relevant genes in the 14 azole -resisting separate with those in the sensitive kind race ATCC 10231, Saccharomyces cerevisiae AD/CDR1, and AD/CDR2 (24). The results of this study indicated that extracts of T. polium and C. colocynthis, especially C. colocynthis extract, collected from Sistan region, showed good antimicrobial activity against Candida albi-…”

The Etest Performed Directly on Blood Culture Bottles Is a Reliable Tool for Detection of Fluconazole-Resistant Candida albicans Isolates

“…2a). Point mutations in ERG11 and ERG3 were found in most isolates, although only 2 isolates had mutations in ERG11, which has been reported to confer resistance (15,28,29). The remaining mutations were also previously described in fluconazole-susceptible isolates and do not seem to play a major role in resistance (15,(30)(31)(32).…”