Dataset Information

Gain-of-function mutations in the transcription factor MRR1 are responsible for overexpression of the MDR1 efflux pump in fluconazole-resistant Candida dubliniensis strains.

ABSTRACT: Candida dubliniensis, a yeast that is closely related to Candida albicans, can rapidly develop resistance to the commonly used antifungal agent fluconazole in vitro and in vivo during antimycotic therapy. Fluconazole resistance in C. dubliniensis is usually caused by constitutive overexpression of the MDR1 gene, which encodes a multidrug efflux pump of the major facilitator superfamily. The zinc cluster transcription factor Mrr1p has recently been shown to control MDR1 expression in C. albicans in response to inducing stimuli, and gain-of-function mutations in the MRR1 gene result in constitutive upregulation of the MDR1 efflux pump. We identified a gene with a high degree of similarity to C. albicans MRR1 (CaMRR1) in the C. dubliniensis genome sequence. When C. dubliniensis MRR1 (CdMRR1) was expressed in C. albicans mrr1Delta mutants, it restored benomyl-inducible MDR1 expression, demonstrating that CdMRR1 is the ortholog of CaMRR1. To investigate whether MDR1 overexpression in C. dubliniensis is caused by mutations in MRR1, we sequenced the MRR1 alleles from a fluconazole-resistant, clinical C. dubliniensis isolate and a matched, fluconazole-susceptible isolate from the same patient as well as those from four in vitro-generated, fluconazole-resistant C. dubliniensis strains derived from two different C. dubliniensis isolates. We found that all five resistant strains contained single nucleotide substitutions or small in-frame deletions that resulted in amino acid changes in Mrr1p. Expression of these mutated alleles in C. albicans resulted in the constitutive activation of the MDR1 promoter and multidrug resistance. Therefore, mutations in MRR1 are the major cause of MDR1 upregulation in both C. albicans and C. dubliniensis, demonstrating that the transcription factor Mrr1p plays a central role in the development of drug resistance in these human fungal pathogens.

SUBMITTER: Schubert S

PROVIDER: S-EPMC2592883 | biostudies-other | 2008 Dec

REPOSITORIES: biostudies-other

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Gain-of-function mutations in the transcription factor MRR1 are responsible for overexpression of the MDR1 efflux pump in fluconazole-resistant Candida dubliniensis strains.

Schubert Sabrina S Rogers P David PD Morschhäuser Joachim J

Antimicrobial agents and chemotherapy 20080922 12

Candida dubliniensis, a yeast that is closely related to Candida albicans, can rapidly develop resistance to the commonly used antifungal agent fluconazole in vitro and in vivo during antimycotic therapy. Fluconazole resistance in C. dubliniensis is usually caused by constitutive overexpression of the MDR1 gene, which encodes a multidrug efflux pump of the major facilitator superfamily. The zinc cluster transcription factor Mrr1p has recently been shown to control MDR1 expression in C. albicans ...[more]

PMID: 18809934

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Project description:The contribution of fluconazole-resistant Candida spp. isolates to urinary tract infections in Egypt has become a nationwide problem. A recent approach to overcome such disaster is combining conventional antifungals with non-antifungals. This study investigated the interaction of amikacin with fluconazole against resistant Candida strains isolated from the urine culture of patients admitted to Alexandria Main University Hospital. Among the collected Candida spp. isolates, 42.9% were resistant to fluconazole with MICs ranging between 128 and 1,024 μg/ml. The resistance-modifying activity of amikacin (4,000 μg/ml) was studied against fluconazole-resistant isolates where amikacin sensitized 91.7 % of resistant Candida spp. isolates to fluconazole with a modulation factor ranging between 32 and 256. The rhodamine efflux assay was performed to examine the impact of amikacin on efflux pump activity. After 120 minutes of treatment, amikacin affected the efflux pump activity of the isolates tested with a percentage of reduction in the fluorescence intensity of 8.9%. Quantitative real-time PCR was applied to assess the amikacin effect on the expression of the efflux pump genes MDR1, CDR1, and CDR2. The downregulatory effect of amikacin on the expression of the studied genes caused a percentage of reduction in the expression level ranging between 42.1 and 94%. In conclusion, amikacin resensitized resistant Candida spp. isolates to fluconazole and could be used in combination in the management of candiduria with a higher efficiency or at lower administration doses. To the best of our knowledge, this is the first study evaluating the enhancement of fluconazole activity in combination with amikacin against Candida spp.The contribution of fluconazole-resistant Candida spp. isolates to urinary tract infections in Egypt has become a nationwide problem. A recent approach to overcome such disaster is combining conventional antifungals with non-antifungals. This study investigated the interaction of amikacin with fluconazole against resistant Candida strains isolated from the urine culture of patients admitted to Alexandria Main University Hospital. Among the collected Candida spp. isolates, 42.9% were resistant to fluconazole with MICs ranging between 128 and 1,024 μg/ml. The resistance-modifying activity of amikacin (4,000 μg/ml) was studied against fluconazole-resistant isolates where amikacin sensitized 91.7 % of resistant Candida spp. isolates to fluconazole with a modulation factor ranging between 32 and 256. The rhodamine efflux assay was performed to examine the impact of amikacin on efflux pump activity. After 120 minutes of treatment, amikacin affected the efflux pump activity of the isolates tested with a percentage of reduction in the fluorescence intensity of 8.9%. Quantitative real-time PCR was applied to assess the amikacin effect on the expression of the efflux pump genes MDR1, CDR1, and CDR2. The downregulatory effect of amikacin on the expression of the studied genes caused a percentage of reduction in the expression level ranging between 42.1 and 94%. In conclusion, amikacin resensitized resistant Candida spp. isolates to fluconazole and could be used in combination in the management of candiduria with a higher efficiency or at lower administration doses. To the best of our knowledge, this is the first study evaluating the enhancement of fluconazole activity in combination with amikacin against Candida spp.

Dataset Information

Gain-of-function mutations in the transcription factor MRR1 are responsible for overexpression of the MDR1 efflux pump in fluconazole-resistant Candida dubliniensis strains.

Publications

Gain-of-function mutations in the transcription factor MRR1 are responsible for overexpression of the MDR1 efflux pump in fluconazole-resistant Candida dubliniensis strains.

Similar Datasets

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