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      Synergistic combination of violacein and azoles that leads to enhanced killing of major human pathogenic dermatophytic fungi Trichophyton rubrum

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          Abstract

          Superficial mycoses caused by dermatophytic fungi such as Trichophyton rubrum represent the most common type of worldwide human infection affecting various keratinized tissues in our body such as the skin, hair, and nails, etc. The dermatophytic infection is a significant public health threat due to its persistent nature and high recurrence rates, and thus alternative treatments to cure this fungal infection are urgently required. The present study mainly focused on the synergistic activity of violacein with four azole drugs (ketoconazole, fluconazole, clotrimazole, and itraconazole) against T. rubrum. The synergistic antifungal activities of violacein and azoles were measured by checkerboard microdilution and time-kill assays. In our study, combinations of violacein and azoles predominantly recorded synergistic effect (FIC index < 0.5). Significant synergistic value was recorded by the combination of violacein and clotrimazole. Time-kill assay by the combination of MIC concentration of violacein and azoles recorded that the growth of the T. rubrum was significantly arrested after 4–12 h of treatment. The combination of violacein and azoles leads to the enhanced inhibition of mycelial growth and conidial germination. Moreover combination enhanced the rate of release of intracellular materials. Morphological changes by SEM analysis were also prominent with the combination. A normal human cell line [Foreskin (FS) normal fibroblast] was used to check the cytotoxicity of violacein. Interestingly violacein recorded no cytotoxicity up to 100 μg/ml. The in vitro synergistic effect of violacein and azoles against clinically relevant fungi, T. rubrum, is reported here for the first time. Finally, our findings support the potential use of the violacein as an antifungal agent especially against dermatophytic fungi T. rubrum.

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          Natural products: an evolving role in future drug discovery.

          The therapeutic areas of infectious diseases and oncology have benefited from abundant scaffold diversity in natural products, able to interact with many specific targets within the cell and indeed for many years have been source or inspiration for the majority of FDA approved drugs. The present review describes natural products (NPs), semi-synthetic NPs and NP-derived compounds that have undergone clinical evaluation or registration from 2005 to 2010 by disease area i.e. infectious (bacterial, fungal, parasitic and viral), immunological, cardiovascular, neurological, inflammatory and related diseases and oncology. Copyright © 2011 Elsevier Masson SAS. All rights reserved.
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            Synergistic effect of calcineurin inhibitors and fluconazole against Candida albicans biofilms.

            Calcineurin is a Ca2+-calmodulin-activated serine/threonine-specific protein phosphatase that governs multiple aspects of fungal physiology, including cation homeostasis, morphogenesis, antifungal drug susceptibility, and virulence. Growth of Candida albicans planktonic cells is sensitive to the calcineurin inhibitors FK506 and cyclosporine A (CsA) in combination with the azole antifungal fluconazole. This drug synergism is attributable to two effects: first, calcineurin inhibitors render fluconazole fungicidal rather than simply fungistatic, and second, membrane perturbation by azole inhibition of ergosterol biosynthesis increases intracellular calcineurin inhibitor concentrations. C. albicans cells in biofilms are up to 1,000-fold more resistant to fluconazole than planktonic cells. In both in vitro experiments and in an in vivo rat catheter model, C. albicans cells in biofilms were resistant to individually delivered fluconazole or calcineurin inhibitors but exquisitely sensitive to the combination of FK506-fluconazole or CsA-fluconazole. C. albicans strains lacking FKBP12 or expressing a dominant FK506-resistant calcineurin mutant subunit (Cnb1-1) formed biofilms that were resistant to FK506-fluconazole but susceptible to CsA-fluconazole, demonstrating that drug synergism is mediated via direct calcineurin inhibition. These findings reveal that calcineurin contributes to fluconazole resistance of biofilms and provide evidence that synergistic drug combinations may prove efficacious as novel therapeutic interventions to treat or prevent biofilms.
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              Potent antifungal activity of extracts and pure compound isolated from pomegranate peels and synergism with fluconazole against Candida albicans.

              Activity-guided repeated fractionation of crude hydro alcoholic extract prepared from the fruit peel of Punica granatum on a silica-gel column yielded a compound that exhibited strong antifungal activity against Candida spp. Based on spectral analyses, the compound was identified as punicalagin. Punicalagin showed strong activity against Candida albicans and Candida parapsilosis, with MICs of 3.9 and 1.9 microg/ml, respectively. The combination of punicalagin and fluconazole showed a synergistic interaction. MIC for fluconazole decreased twofold when combined with the extract. The FIC index was 0.25. The synergism observed in disk-diffusion and checkerboard assays was confirmed in time-kill curves. The effect of punicalagin on the morphology and ultrastructure in treated yeast cells was examined by scanning and transmission electron microscopy. An irregular budding pattern and pseudohyphae were seen in treated yeasts. By transmission electron microscopy, treated cells showed a thickened cell wall, changes in the space between cell wall and the plasma membrane, vacuoles, and a reduction in cytoplasmic content. Since the punicalagin concentration effective in vitro is achievable in vivo, the combination of this agent with fluconazole represents an attractive prospect for the development of new management strategies for candidiasis, and should be investigated further in in vivo models. Crown Copyright 2010. Published by Elsevier SAS. All rights reserved.
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                Author and article information

                Contributors
                Journal
                Front Cell Infect Microbiol
                Front Cell Infect Microbiol
                Front. Cell. Infect. Microbiol.
                Frontiers in Cellular and Infection Microbiology
                Frontiers Media S.A.
                2235-2988
                11 August 2015
                2015
                : 5
                : 57
                Affiliations
                [1] 1Environmental Technology, CSIR-National Institute for Interdisciplinary Science and Technology Thiruvananthapuram, India
                [2] 2Agroprocessing and Natural Products Division, CSIR-National Institute for Interdisciplinary Science and Technology Thiruvananthapuram, India
                Author notes

                Edited by: Yongqun He, University of Michigan Medical School, USA

                Reviewed by: Ludmila Baltazar, Albert Einstein College of Medicine of Yeshiva College, USA; Bala Nambisan, Central Tuber Crops Research Institute, India

                *Correspondence: B. S. Dileep Kumar, Agroprocessing and Natural Products Division, CSIR-National Institute for Interdisciplinary Science and Technology, Estate P.O., Pappanamcode, Thiruvananthapuram 695019, India kumardileep@ 123456niist.res.in
                Article
                10.3389/fcimb.2015.00057
                4531294
                7b3b8015-2fcc-4ff6-94a2-ffb28d36098d
                Copyright © 2015 Anju, Kumar, Krishnakumar and Dileep Kumar.

                This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

                History
                : 05 June 2015
                : 21 July 2015
                Page count
                Figures: 8, Tables: 1, Equations: 0, References: 36, Pages: 11, Words: 6690
                Categories
                Microbiology
                Original Research

                Infectious disease & Microbiology
                azoles,dermatophytosis,trichophyton rubrum,violacein,synergistic
                Infectious disease & Microbiology
                azoles, dermatophytosis, trichophyton rubrum, violacein, synergistic

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