Characterisation of an ABC transporter of a resistant Candida glabrata clinical isolate

BACKGROUND Candida glabrata ranks second in epidemiological surveillance studies, and is considered one of the main human yeast pathogens. Treatment of Candida infections represents a contemporary public health problem due to the limited availability of an antifungal arsenal, toxicity effects and increasing cases of resistance. C. glabrata presents intrinsic fluconazole resistance and is a significant concern in clinical practice and in hospital environments. OBJECTIVE The aim of this study was to characterise the azole resistance mechanism presented by a C. glabrata clinical isolate from a Brazilian university hospital. METHODS Azole susceptibility assays, chemosensitisation, flow cytometry and mass spectrometry were performed. FINDINGS Our study demonstrated extremely high resistance to all azoles tested: fluconazole, voriconazole, posaconazole and itraconazole. This isolate was chemosensitised by FK506, a classical inhibitor of ABC transporters related to azole resistance, and Rhodamine 6G extrusion was observed. A mass spectrometry assay confirmed the ABC protein identification suggesting the probable role of efflux pumps in this resistance phenotype. MAIN CONCLUSIONS This study emphasizes the importance of ABC proteins and their relation to the resistance mechanism in hospital environments and they may be an important target for the development of compounds able to unsettle drug extrusion.

Synthetic organotelluride compounds induce the reversal of Pdr5p mediated fluconazole resistance in Saccharomyces cerevisiae

Background: Resistance to fluconazole, a commonly used azole antifungal, is a challenge for the treatment of fungal infections. Resistance can be mediated by overexpression of ABC transporters, which promote drug efflux that requires ATP hydrolysis. the Pdr5p ABC transporter of Saccharomyces cerevisiae is a well-known model used to study this mechanism of antifungal resistance. the present study investigated the effects of 13 synthetic compounds on Pdr5p.Results: Among the tested compounds, four contained a tellurium-butane group and shared structural similarities that were absent in the other tested compounds: a lateral hydrocarbon chain and an amide group. These four compounds were capable of inhibiting Pdr5p ATPase activity by more than 90%, they demonstrated IC50 values less than 2 M and had an uncompetitive pattern of Pdr5p ATPase activity inhibition. These organotellurides did not demonstrate cytotoxicity against human erythrocytes or S. cerevisiae mutant strains (a strain that overexpress Pdr5p and a null mutant strain) even in concentrations above 100 mu M. When tested at 100 mu M, they could reverse the fluconazole resistance expressed by both the S. cerevisiae mutant strain that overexpress Pdr5p and a clinical isolate of Candida albicans.Conclusions: We have identified four organotellurides that are promising candidates for the reversal of drug resistance mediated by drug efflux pumps. These molecules will act as scaffolds for the development of more efficient and effective efflux pump inhibitors that can be used in combination therapy with available antifungals.Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)University of São Paulo through the NAP-CatSinQ (Research Core in Catalysis and Chemical Synthesis)Univ Fed Rio de Janeiro, CCS, Inst Microbiol Paulo Goes, Dept Microbiol Geral,Lab Bioquim Microbiana, Rio de Janeiro, RJ, BrazilUniv São Paulo, Inst Quim, Dept Quim Fundamental, São Paulo, BrazilInst Fed Educ Ciencia & Tecnol Rio de Janeiro IFR, Rio de Janeiro, RJ, BrazilUniversidade Federal de São Paulo UNIFESP, Inst Ciencias Ambientais Quim & Farmaceut, São Paulo, BrazilUniversidade Federal de São Paulo UNIFESP, Inst Ciencias Ambientais Quim & Farmaceut, São Paulo, BrazilFAPERJ: E-26/111.338/2013FAPESP: 2005/59572-7FAPESP: 2008/55401-1FAPESP: 2010/17228-6FAPESP: 2011/03244-2FAPESP: 2011/11613-8FAPESP: 2012/17093-9CNPq: 470360/2012-7Web of Scienc

Characterisation of an ABC transporter of a resistant Candida glabrata clinical isolate

BACKGROUND Candida glabrata ranks second in epidemiological surveillance studies, and is considered one of the main human yeast pathogens. Treatment of Candida infections represents a contemporary public health problem due to the limited availability of an antifungal arsenal, toxicity effects and increasing cases of resistance. C. glabrata presents intrinsic fluconazole resistance and is a significant concern in clinical practice and in hospital environments. OBJECTIVE The aim of this study was to characterise the azole resistance mechanism presented by a C. glabrata clinical isolate from a Brazilian university hospital. METHODS Azole susceptibility assays, chemosensitisation, flow cytometry and mass spectrometry were performed. FINDINGS Our study demonstrated extremely high resistance to all azoles tested: fluconazole, voriconazole, posaconazole and itraconazole. This isolate was chemosensitised by FK506, a classical inhibitor of ABC transporters related to azole resistance, and Rhodamine 6G extrusion was observed. A mass spectrometry assay confirmed the ABC protein identification suggesting the probable role of efflux pumps in this resistance phenotype. MAIN CONCLUSIONS This study emphasizes the importance of ABC proteins and their relation to the resistance mechanism in hospital environments and they may be an important target for the development of compounds able to unsettle drug extrusion