Quantitation of ergosterol content and gene expression profile of ERG11 gene in fluconazole-resistant Candida albicans

Background and The frequency of opportunistic fungal infections in immunocompromised patients, especially by Candida species, has sharply increased in the last few decades. The objective of this study was to analyse the ergosterol content and gene expression profiling of clinical isolates of fluconazole resistant Candida albicans.
Sixty clinical samples were identified and collected from immunocompromised patients, namely recurrent oral, vaginal, and cutaneous candidiasis, during 2015-16. Antifungal susceptibility testing of fluconazole against clinical Candida species was performed according to Clinical and Laboratory Standards Institute guidelines. Ergosterol content and gene expression profiling of sterol 14α-demethylase (ERG11) gene in fluconazole-susceptible and –resistant C.albicans were investigated.
The specimens consisted of C. albicans (46.67%), Candida krusei (41.67%) (and Candida tropicalis (11.67%). All the isolates were resistant to fluconazole. No significant reduction was noted in total cellular ergosterol content in comparison with untreated controls in terms of fluconazole-resistant C. albicans. The expression level of ERG11 gene was down-regulated in fluconazole-susceptible C. albicans.Eventually, the expression pattern of ERG11 gene revealed no significant changes in fluconazole-resistant isolates compared to untreated controls. The results revealed no significant differences between fluconazole-susceptible and –resistant C. albicans sequences by comparison with ERG11 reference sequence.
Our findings provide an insight into the mechanism of fluconazole resistance in C. albicans. The mechanisms proposed for clinical isolates of fluconazole-resistant C. albicans are alteration in sterol biosynthesis, analysis of expression level of ERG11 gene, and analysis of gene sequences. Nonetheless, further studies are imperative to find molecular mechanisms that could be targeted to control fluconazole resistance.