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Published on: December 28, 2017
Molecular mechanisms associated with Fluconazole resistance in clinical Candida albicans isolates from India
Arati Mane1, Pallavi Vidhate1, Chanchal Kusro1
1National AIDS Research Institute, Pune, Maharashtra, India.
Abstract:
Resistance to azole antifungals is a significant problem in Candida albicans. An understanding of resistance at molecular level is essential for the development of strategies to tackle resistance and rationale design of newer antifungals and target-based molecular approaches. This study presents the first evaluation of molecular mechanisms associated with fluconazole resistance in clinical C.albicans isolates from India. Target site (ERG11) alterations were determined by DNA sequencing, whereas real-time PCRs were performed to quantify target and efflux pump genes (CDR1, CDR2, MDR1) in 87 [Fluconazole susceptible (n = 30), susceptible-dose dependent (n = 30) and resistant (n = 27)] C.albicans isolates. Cross-resistance to fluconazole, ketoconazole and itraconazole was observed in 74.1% isolates. Six amino acid substitutions were identified, including 4 (E116D, F145L, E226D, I437V) previously reported ones and 2 (P406L, Q474H) new ones. CDR1 over-expression was seen in 77.7% resistant isolates. CDR2 was exclusively expressed with CDR1 and their concomitant over-expression was associated with azole cross-resistance. MDR1 and ERG11 over-expression did not seem to be associated with resistance. Our results show that drug efflux mediated by Adenosine-5'-triphosphate (ATP)-binding cassette transporters, especially CDR1 is the predominant mechanism of fluconazole resistance and azole cross-resistance in C. albicans and indicate the need for research directed towards developing strategies to tackle efflux mediated resistance to salvage azoles.
Insights
Drug efflux, particularly via the CDR1 gene, is the primary cause of fluconazole resistance in Candida albicans. This finding is crucial for developing new antifungal strategies against this common infection.
Area of Science:
- Medical Mycology
- Molecular Biology
- Antimicrobial Resistance
Background:
- Azole antifungals are widely used to treat Candida albicans infections.
- Increasing azole resistance poses a significant threat to public health.
- Understanding the molecular basis of resistance is vital for developing effective treatments.
Purpose of the Study:
- To investigate the molecular mechanisms of fluconazole resistance in clinical Candida albicans isolates from India.
- To identify genetic alterations and gene expression patterns associated with resistance.
- To evaluate cross-resistance patterns among different azole antifungals.
Main Methods:
- DNA sequencing of the ERG11 gene to detect target site alterations.
- Real-time PCR to quantify the expression of ERG11, CDR1, CDR2, and MDR1 genes.
- Phenotypic susceptibility testing for fluconazole, ketoconazole, and itraconazole.
Main Results:
- Six amino acid substitutions in ERG11 were identified, including two novel ones (P406L, Q474H).
- Over-expression of CDR1 was observed in 77.7% of resistant isolates.
- Concomitant over-expression of CDR1 and CDR2 was associated with azole cross-resistance.
Conclusions:
- Drug efflux mediated by Adenosine-5'-triphosphate (ATP)-binding cassette transporters, especially CDR1, is the predominant mechanism of fluconazole resistance and azole cross-resistance in Candida albicans.
- Target site mutations in ERG11 are not the primary drivers of resistance in these isolates.
- Further research into strategies targeting efflux pumps is needed to overcome azole resistance.
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