Showing papers on "Antifungal antibiotic published in 2012"

Polyene antibiotic that inhibits membrane transport proteins.

Abstract: The limited therapeutic arsenal and the increase in reports of fungal resistance to multiple antifungal agents have made fungal infections a major therapeutic challenge. The polyene antibiotics are the only group of antifungal antibiotics that directly target the plasma membrane via a specific interaction with the main fungal sterol, ergosterol, often resulting in membrane permeabilization. In contrast to other polyene antibiotics that form pores in the membrane, the mode of action of natamycin has remained obscure but is not related to membrane permeabilization. Here, we demonstrate that natamycin inhibits growth of yeasts and fungi via the immediate inhibition of amino acid and glucose transport across the plasma membrane. This is attributable to ergosterol-specific and reversible inhibition of membrane transport proteins. It is proposed that ergosterol-dependent inhibition of membrane proteins is a general mode of action of all the polyene antibiotics, of which some have been shown additionally to permeabilize the plasma membrane. Our results imply that sterol-protein interactions are fundamentally important for protein function even for those proteins that are not known to reside in sterol-rich domains.

Corifungin, a New Drug Lead against Naegleria, Identified from a High-Throughput Screen

Abstract: Primary amebic meningoencephalitis (PAM) is a rapidly fatal infection caused by the free-living ameba Naegleria fowleri. The drug of choice in treating PAM is the antifungal antibiotic amphotericin B, but its use is associated with severe adverse effects. Moreover, few patients treated with amphotericin B have survived PAM. Therefore, fast-acting and efficient drugs are urgently needed for the treatment of PAM. To facilitate drug screening for this pathogen, an automated, high-throughput screening methodology was developed and validated for the closely related species Naegleria gruberi. Five kinase inhibitors and an NF-kappaB inhibitor were hits identified in primary screens of three compound libraries. Most importantly for a preclinical drug discovery pipeline, we identified corifungin, a water-soluble polyene macrolide with a higher activity against Naegleria than that of amphotericin B. Transmission electron microscopy of N. fowleri trophozoites incubated with different concentrations of corifungin showed disruption of cytoplasmic and plasma membranes and alterations in mitochondria, followed by complete lysis of amebae. In vivo efficacy of corifungin in a mouse model of PAM was confirmed by an absence of detectable amebae in the brain and 100% survival of mice for 17 days postinfection for a single daily intraperitoneal dose of 9 mg/kg of body weight given for 10 days. The same dose of amphotericin B did not reduce ameba growth, and mouse survival was compromised. Based on these results, the U.S. FDA has approved orphan drug status for corifungin for the treatment of PAM.

Leishmanicidal and Anticandidal Activity of Constituents of Indian Edible Mushroom Astraeus hygrometricus

Abstract: Two new lanostane-type triterpenes, 1 and 2, were isolated from Astraeus hygrometricus. The structures were established by IR, (1)H- and (13)C-NMR, MS, and X-ray crystallographic experiments. The triterpenes exhibited excellent in vitro toxicities against Candida albicans, comparable to standard antifungal antibiotics. The triterpene 2 significantly inhibited the growth of Leishmania donovani promastigotes in vitro. The triterpene skeleton may be considered a template structure in search for new compounds with anticandidal and leishmanicidal activity.

Waikialoid A suppresses hyphal morphogenesis and inhibits biofilm development in pathogenic Candida albicans.

Abstract: A chemically prolific strain of Aspergillus was isolated from a soil sample collected near Waikiki Beach, Honolulu, Hawaii. The fungus produced several secondary metabolites, which were purified and placed in our natural products library and were later screened for substances capable of inhibiting biofilm formation by Candida albicans. It was determined that one of the secondary metabolites from the Hawaiian fungal isolate, a new complex prenylated indole alkaloid named waikialoid A (1), inhibited biofilm formation with an IC(50) value of 1.4 μM. Another structurally unrelated, presumably polyketide metabolite, waikialide A (15), also inhibited C. albicans biofilm formation, but was much less potent (IC(50) value of 32.4 μM). Microscopy studies revealed that compound 1 also inhibited C. albicans hyphal morphogenesis. While metabolite 1 appears ineffective at disrupting preformed biofilms, the accumulated data indicate that the new compound may exert its activity against C. albicans during the early stages of surface colonization involving cell adherence, hyphal development, and/or biofilm assembly. Unlike some other stephacidin/notoamide compounds, metabolite 1 was not cytotoxic to fungi or human cells (up to 200 μM), which makes this an intriguing model compound for studying the adjunctive use of biofilm inhibitors in combination with standard antifungal antibiotics.

Structural analysis and biosynthetic engineering of a solubility-improved and less-hemolytic nystatin-like polyene in Pseudonocardia autotrophica

Abstract: Polyene antibiotics such as nystatin are a large family of very valuable antifungal polyketide compounds typically produced by soil actinomycetes. Previously, using a polyene cytochrome P450 hydroxylase-specific genome screening strategy, Pseudonocardia autotrophica KCTC9441 was determined to contain an approximately 125.7-kb region of contiguous DNA with a total of 23 open reading frames, which are involved in the biosynthesis and regulation of a structurally unique polyene natural product named NPP. Here, we report the complete structure of NPP, which contains an aglycone identical to nystatin and harbors a unique di-sugar moiety, mycosaminyl-(α1-4)-N-acetyl-glucosamine. A mutant generated by inactivation of a sole glycosyltransferase gene (nppDI) within the npp gene cluster can be complemented in trans either by nppDI-encoded protein or by its nystatin counterpart, NysDI, suggesting that the two sugars might be attached by two different glycosyltransferases. Compared with nystatin (which bears a single sugar moiety), the di-sugar containing NPP exhibits approximately 300-fold higher water solubility and 10-fold reduced hemolytic activity, while retaining about 50% antifungal activity against Candida albicans. These characteristics reveal NPP as a promising candidate for further development into a pharmacokinetically improved, less-cytotoxic polyene antifungal antibiotic.

Isolation and total synthesis of icumazoles and noricumazoles--antifungal antibiotics and cation-channel blockers from Sorangium cellulosum.

Abstract: Myxobacteria are a potent source of secondary metabolites of which the genus Sorangium has yielded the largest number. In the course of our ongoing bioactivity-guided screening program, an unknown antifungal spectrum of activity was detected in the extract of S. cellulosum, So ce701, and led to the isolation of the unique isochromanoneand oxazole-containing icumazoles (1a–c). Later the same characteristic structural element was rediscovered in the noricumazoles (2 a,b). Here, we provide a concise report on the icumazoles (1a– c) and noricumazoles (2a–c) which covers their isolation and structure elucidation as well as studies on their ion-channelinhibitory properties. We approached these goals utilizing a broad range of strategies based on various spectroscopic methods and the chemical determination of relative and absolute configurations by derivatization, degradation, and fragment synthesis, and unequivocally by the total synthesis of noricumazole A (2a). In addition, we provide evidence for the ion-channel-inhibitory effect of noricumazole A (2 a) utilizing a new screening concept for oligomeric ion channels. For the production of icumazoles (1a–c) the producer was cultivated at 30 8C for 14 days in a 100 L fermentor, and icumazoles were isolated as described in the Supporting Information. Icumazoles (1a–c) are easily recognized in UPLC-DAD-UV analyses (ultra-performance liquid chromatography with diode array UV detection) by their UV spectra, especially by the intense main absorption at 302 nm with side bands at 290 and 316 nm, which are characteristic for conjugated short polyenes. In the high-resolution ESIMS, the signal for the molecular ion M of the peak eluting at Rt = 15.37 min indicated the molecular formula C33H45NO7 for icumazole A (1a), which was fully compatible with the NMR data (Table S1 in the Supporting Information). The 33 carbon signals in the C NMR spectrum were classified according to the DEPT spectrum, and three heteroatom-bound exchangeable protons were calculated, which were not visible in the H NMR spectra in [D4]MeOH. All protons in the H NMR spectra could be unambiguously assigned to their corresponding carbon atoms from their correlations in the H,C HMQC spectrum. The correlations in the H,H COSY spectrum provided four major domains (A–D; Figure 1). The remaining unsaturated methine singlet (H19, dH/C = 7.80/138.0 ppm) was recognized as part of a heteroaromatic ring because of its large JHC coupling constant of 209 Hz. Along with the quaternary carbon atoms C18 and C20 next to one nitrogen and one oxygen atom, this methine C19 forms an oxazole

Biochemical characterization of an anti-Candida factor produced by Enterococcus faecalis

Abstract: Because Candida albicans is resistant to several antifungal antibiotics, there is a need to identify other less toxic natural products, particularly antimicrobial proteins, peptides or bacteriocin like inhibitory substances. An attempt has been made to purify and characterise an anti-Candida compound produced by Enterococcus faecalis. An anti-Candida protein (ACP) produced by E. faecalis active against 8 C. albicans strains was characterised and partially purified. The ACP showed a broad-spectrum activity against multidrug resistant C. albicans MTCC 183, MTCC 7315, MTCC 3958, NCIM 3557, NCIM 3471 and DI. It was completely inactivated by treatment with proteinase K and partially by pronase E. The ACP retained biological stability after heat-treatment at 90°C for 20 min, maintained activity over a pH range 6–10, and remained active after treatment with α-amylase, lipase, organic solvents, and detergents. The antimicrobial activity of the E. faecalis strain was found exclusively in the extracellular filtrate produced in the late logarithmic growth phase. The highest activity (1600 AU mL-1) against C. albicans MTCC 183 was recorded at 48 h of incubation, and activity decreased thereafter. The peptide showed very low haemagglutination and haemolytic activities against human red blood cells. The antimicrobial substance was purified by salt-fractionation and chromatography. Partially purified ACP had a molecular weight of approximately 43 KDa in Tricine-PAGE analysis. The 12 amino acid N terminal sequence was obtained by Edman degradation. The peptide was de novo sequenced by ESI-MS, and the deduced combined sequence when compared to other bacteriocins and antimicrobial peptide had no significant sequence similarity. The inhibitory activity of the test strain is due to the synthesis of an antimicrobial protein. To our knowledge, this is the first report on the isolation of a promising non-haemolytic anti-Candida protein from E. faecalis that might be used to treat candidiasis especially in immunocompromised patients.

Isolation and characterization of Bacillus sp. producing broad-spectrum antibiotics against human and plant pathogenic fungi.

Abstract: A strain of bacterium producing antifungal antibiotic was isolated and identification of the strain was attempted. We could identify the bacterium as being a Bacillus sp., based on morphological observation, physiological characteristics, and 16S rDNA sequence analysis, thus leading us to designate the strain as Bacillus sp. AH-E-1. The strain showed potent antibiotic activity against phytopathogenic and human pathogenic fungi by inducing mycelial distortion and swelling and inhibiting spore germination. The antibiotic metabolite produced by the strain demonstrated excellent thermal and pH (2-11) stability, but was labile to autoclaving. From these results, we could find a broader antifungal activity of Bacillus genus. Isolation and characterization of the active agent produced by the strain are under progress.

Role of Plant-Growth-Promoting Rhizobacteria in the Management of Cadmium-Contaminated Soil

Abstract: During the last decades, heavy metals have become a common contaminant worldwide. Root-colonizing bacteria that exert beneficial effects on plant development directly or indirectly, often called as plant-growth-promoting rhizobacteria (PGPR), play an important role in the remediation of heavy-metal-contaminated soils. The prospect of manipulating rhizosphere microbial populations by inoculating beneficial bacteria to increase plant growth has shown considerable promise in laboratory and greenhouse studies, but responses have been variable under the field trials. In addition to their role in metal decontamination/removal, PGPR have also been found to facilitate plant growth in conventional soils by various mechanisms. These mechanisms include the suppression of phytopathogens by producing siderophores, synthesizing antifungal antibiotics, secreting fungal cell-wall-lysing enzymes, or hydrogen cyanide in addition to the release of growth-promoting hormones, solubilization of insoluble phosphate, and providing other essential nutrients to plants. Here in this chapter, the role of PGPR in metal especially cadmium decontamination is highlighted.

Development and evaluation of a self-emulsifying drug delivery system of amphotericin B

Abstract: Amphotericin B is a polyene antifungal antibiotic belonging to Class IV of Biopharmaceutics Classification System which is not absorbed from the gastrointestinal tract after oral administration. The aim of this research work was to develop a self-emulsifying drug delivery system (SEDDS) of amphotericin B and to evaluate the dissolution and permeability of amphotericin B from the formulation. The solubility of amphotericin B in various oils, surfactants and cosurfactants was determined.Various SEDDS formulations were prepared with varying amounts of oil, surfactant and co-surfactant. Evaluation parameters for formulation optimization were drug content, self-emulsification, droplet size analysis, and precipitation studies. In vitro dissolution was studied in comparison to the pure drug. Permeability was studied using non-everted intestinal sac method. The optimized formulation consisted of glycerol mono-oleate (10%, w/w), tween 80 (36%, w/w), polyethylene glycol 400 (27%, w/w), and propylene glycol (27%, w/w) with a drug content of about 8 mg per ml. The self-emulsifying formulation showed 100% dissolution within 30 minutes whereas the pure drug exhibited a very poor rate of dissolution.In vitro intestinal permeability was studied by noneverted intestinal sac method using rat intestine. The self-emulsifying formulation showed 100% drug permeation within 30 minutes compared to negligible permeation from the drug suspension. The study demonstrates that SEDDS approach may be useful for enhancement of dissolution and intestinal permeation of amphotericin B belonging to class IV of Biopharmaceutic Classification System.

Total synthesis of the antifungal antibiotic PF1163A

Abstract: The total synthesis of a novel antifungal antibiotic PF1163A is reported utilising Keck asymmetric allylation, Sharpless kinetic resolution, regioselective epoxide-ring opening, esterification and ring-closing metathesis as the key reactions.

Antifungal antibiotic production by streptomyces sp. isolated from soil

Abstract: Actinomycetes isolate were obtained from soils samples collected from various ecological niches of Western Uttar Pradesh (Meerut). They were selected for their antimicrobial producing capabilities against some selected microbial strains including fungus (Aspergillus sp.), Yeast (Candida sp.), gram- stain-positive bacteria (Bacillus sp.) and gram-stain-negative bacteria (Burkholderia sp.). Out of 19 isolates, 12 (63%) were found to have antimicrobial activity, among them 53% and 26% isolates were found active against gram-stain-positive and gram-stain-negative bacteria, respectively. Antifungal activity was recorded in 42% isolates, among them 32% were active against Aspergillus sp. and 11% were found active against Candida sp. Only one isolate (SS12) was found to produce broad spectrum antibiotic effective against all test microorganisms. 16S rDNA sequencing and BIOLOG analysis of SS12 suggested that it may be a novel species of genus Streptomyces.

Streptomyces scabiei subsp. xuchangensis, A NOVEL STREPTOMYCETE ISOLATE FOR STAUROSPORINE PRODUCTION AND A WHEAT TAKE-ALL CONTROL AGENT

Abstract: The streptomycete strain SCY114 was isolated from a soil sample of Xuchang in Henan province, China. It possessed smooth grey spores borne in rectiflexible and spiral chains and was capable of using all of the International Streptomyces Project sugars. The melting temperature and G+C content were 81.8℃ and 61.6 mol%, respectively. The level of 16S rRNA gene sequence similarity be- tween strain SCY114 and S. scabies ATCC49173 was 99.8%. However, the values of DNA-DNA relatedness between strain SCY114 and S. scabies ATCC49173 was 65.2%, and the strain SCY114 did not exhibit pathogenicity towards potato plants. Based on the pheno- typic and genotypic evidence, strain SCY114 was identified as a subspecies of the Streptomyces scabiei, for which the name Streptomy- ces scabiei subsp. xuchangensis is proposed. Strain SCY114 strongly inhibited the in vitro mycelial growth of Gaeumannomyces graminis var. tritici as well as various other plant pathogenic fungi. The filtered culture broth of strain SCY114 was substantially more effective at controlling wheat take-all compared to the silthiofam, and the disease was reduced by 78.2%. An antifungal antibiotic was isolated from the fermentation broth of strain SCY114 using a series of chromatographic procedures. The molecular formula of the antibiotic was deter- mined to be C28H26N4O3, and on the basis of the NMR data, the antibiotic was confirmed to be staurosporine.

Identification and separation of the novel antifungal antibiotic of streptomyces hygroscopicus BOS-013 strain by Simulated Moving Bed Chromatography

Abstract: BOS-013 actinomycete strain was obtained by separating difference soil of areas from ChangBai Mountain. The antifungal antibiotic produced by Streptomyces Hygroscopicus BOS-013 was firstly purified by means of macro-porous adsorbent resin and thin-layer chromatography. Separation and Purification of the antifungal antibiotic from its fermentation broth of streptomyces hygroscopicus BOS-013 strain were further carried out by Simulated Moving Bed Chromatography and then the crystal of the antibiotic with high purity was got. In this paper, the methods of purification by adsorbing of micro-porous adsorbent resin and detection by high performance liquid chromatography were established. The exact structure of the antibiotic was identified by mass spectrometry and NMR spectra.

Screen of Streptomyces Hygroscopicus BOS-013 Strain and Identification of the Antifungal Antibiotic from Its Fermentation Broth

Abstract: BOS-013 actinomycete strain was obtained by separating different kinds of soils from the nature. Moreover, the morphology, cultural characteristics, physiological-biochemical characteristics and 16S rDNA sequences of this strain were studied. A phylogenetic tree was constructed by comparing with the published 16S rDNA sequences of the related species and showed 99% identity of nucleotide sequence of 16S rDNA with Streptomyces hygroscopicus. The antifungal Biotic produced by Streptomyces Hygroscopicus BOS-013 was purified by means of macro-porous adsorbent resin, and the crystal of the antibiotic with high purity was got. In this paper, the methods of purification by adsorbing of microporous adsorbent resin and detection by high performance liquid chromatography with mass spectrum (HPLC-MS) were established. The study would be laid a good foundation for its physical-chemical properties. Meanwhile, we identified its structure by spectral analyses. The result appeared that the optimal eluant was 50% ethanol. The best developing agent in thin-layer chromatography was Petroleum ether: ethyl acetate (5:1, v / v). Quasi-molecular ion peak [M+H]+ was 547 given by positive ion mode-electrospray ionization-mass spectrometry and pushed-out its molecular weight was 546. Meanwhile we exserted its molecular formula was C30H43O9 combined with NMR spectrum. We did not find this compound, so it was infered as a new compound temporarily after Scifinder search.

Identification and Separation of the Novel Antifungal Antibiotic of Streptomyces Hygroscopicus BOS-013 Strain by Simulated Moving Bed Chromatography

Abstract: BOS-013 actinomycete strain was obtained by separating difference soil of areas from ChangBai Mountain. The antifungal antibiotic produced by Streptomyces Hygroscopicus BOS-013 was firstly purified by means of macro-porous adsorbent resin and thin-layer chromatography. Separation and Purification of the antifungal antibiotic from its fermentation broth of streptomyces hygroscopicus BOS-013 strain were further carried out by Simulated Moving Bed Chromatography and then the crystal of the antibiotic with high purity was got. In this paper, the methods of purification by adsorbing of micro-porous adsorbent resin and detection by high performance liquid chromatography were established. The exact structure of the antibiotic was identified by mass spectrometry and NMR spectra.