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.

The effect of 3-(biphenyl-4-yl)-3-hydoxyquinuclidine (BPQ-OH) and metronidazole on Trichomonas vaginalis: a comparative study.

Trichomonas vaginalis causes trichomoniasis in humans, a sexually transmitted disease commonly treated with metronidazole (MTZ), a drug that presents some toxicity, causing undesirable side effects. In addition, an increase in metronidazole-resistant parasites has been reported. Thus, the development of alternative treatment is recommended. To date, the search for antiparasitic drugs has been based on different approaches: identification of active natural products, identification of parasite targets, and the use of available compounds active against other pathogenic microorganisms. Here, we analyzed the in vitro antiproliferative and ultrastructural effects on T. vaginalis of BPQ-OH, a hydroxiquinuclidine derivative that inhibits squalene synthase and is active against several protozoa and fungi. We also compared the effects of BPQ-OH on T. vaginalis and mammalian cells with those of MTZ. We found that BPQ-OH inhibits in vitro proliferation of T. vaginalis, with an IC50 of 46 µM after 24 h. Although this IC50 is 16 times higher than that of MTZ (1.8 µM), BPQ-OH is less toxic for human cell lines than MTZ, with LC50 values of 2,300 and 70 µM, and selective indexes of 50 and 39, respectively. Ultrastructural analyses demonstrated that BPQ-OH induced alterations in T. vaginalis, such as rounded and wrinkled cells, membrane blebbing and intense vacuolization, leading to cell death, whereas MTZ also caused significant changes, including a decrease in hydrogenosomes size and endoflagellar forms. Our observations identify BPQ-OH as a promising leading compound for the development of novel anti-T. vaginalis drugs and highlight the need for further testing this molecule using experimentally infected animals.

Evaluation of the effect of miltefosine on Trichomonas vaginalis.

Trichomonas vaginalis causes trichomoniasis in humans, a sexually transmitted disease commonly treated with metronidazole (MTZ). MTZ is known to cause undesirable side effects, and MTZ-resistant parasites have been reported. Thus, the development of an alternative treatment is desirable. Miltefosine (MLT) is an alkylphosphocholine synthetic lipid analogue that displays antiparasitic activity against Leishmania, Trypanosoma cruzi, Entamoeba histolytica, Acanthamoeba spp., Giardia lamblia, T. vaginalis and some fungi. Moreover, it has been used for oral treatment of visceral leishmaniosis in several countries. Here, we analysed the MLT-induced antiproliferative effect on T. vaginalis as well its effect on the fine structure and viability of the parasite. We observed a dose-dependent effect with an IC50 of 14.5 and 20 µM after 24 and 48 h, respectively. Furthermore, reversibility assays demonstrated that new incubations were necessary in order to maintain the antiproliferative effect. Ultrastructural analyses demonstrated that MLT induced several alterations, including the appearance of wrinkled and rounded cells, membrane blebbing, intense vacuolization and nuclear condensation, all indicative of cell death by apoptosis. In addition, the quantitative analyses of the viability assays using combined markers of live and dead cells demonstrated that treatment with the IC50 concentration of MLT significantly reduced the number of viable parasites compared with untreated cells. Taken together, these observations suggest that MLT is a promising compound for the treatment of trichomoniasis.

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.

Ultrastructural alterations induced by Δ(24(25))-sterol methyltransferase inhibitors on Trichomonas vaginalis.

Trichomonas vaginalis is an important human parasite that causes trichomoniasis, a cosmopolitan sexually transmitted disease. Currently, the treatment of choice for T. vaginalis infections is metronidazole. The increase in metronidazole-resistant parasites and undesirable side effects of this drug make the search for alternative chemotherapeutic approaches a priority for the management of trichomoniasis. Here, the antiproliferative and ultrastructural effects of sterol biosynthesis inhibitors against T. vaginalis were investigated. It was found that 22,26-azasterol (5 µM) and 24(R,S),25-epiminolanosterol (10 µM), known inhibitors of Δ(24(25))-sterol methyltransferase, exhibited antiproliferative effects on T. vaginalis trophozoites cultured in vitro. Morphological analyses showed that azasterols induced changes in the ultrastructure of T. vaginalis. The most significant alterations were (1) membrane blebbing and disruption, (2) wrinkled cells and (3) the formation of cell clusters. In addition, autophagic vacuoles, Golgi duplication arrest, an abnormal Golgi enlargement and damaged hydrogenosomes were also observed. Nonspecific cytotoxicity assays using the cultured mammalian cell lines Madin-Darby canine kidney cells showed no effect of the azasterols on the viability and proliferation of these cells at a concentration that significantly inhibited the proliferation of T. vaginalis, indicating a selective antiparasitic action. Taken together, these results suggest that azasterols could be important compounds in the development of novel chemotherapeutic approaches against T. vaginalis.