Showing papers in "The Journal of Antibiotics in 2014"
TL;DR: This work brings a molecule-centered perspective to the questions of where will new scaffolds come from, when will chemogenetic approaches yield useful new antibiotics and what existing bacterial targets merit contemporary re-examination.
Abstract: There is a continuous need for iterative cycles of antibiotic discovery and development to deal with the selection of resistant pathogens that emerge as therapeutic application of an antibiotic becomes widespread. A short golden age of antibiotic discovery from nature followed by a subsequent golden half century of medicinal chemistry optimization of existing molecular scaffolds emphasizes the need for new antibiotic molecular frameworks. We bring a molecule-centered perspective to the questions of where will new scaffolds come from, when will chemogenetic approaches yield useful new antibiotics and what existing bacterial targets merit contemporary re-examination.
322 citations
TL;DR: The identification, in strains of Escherichia coli, of the positions within β of the mutations determining resistance is discussed in some detail, as are mutations in organisms that are therapeutic targets of RIF, in particular Mycobacterium tuberculosis.
Abstract: Resistance to rifampicin (RIF) is a broad subject covering not just the mechanism of clinical resistance, nearly always due to a genetic change in the β subunit of bacterial RNA polymerase (RNAP), but also how studies of resistant polymerases have helped us understand the structure of the enzyme, the intricacies of the transcription process and its role in complex physiological pathways. This review can only scratch the surface of these phenomena. The identification, in strains of Escherichia coli, of the positions within β of the mutations determining resistance is discussed in some detail, as are mutations in organisms that are therapeutic targets of RIF, in particular Mycobacterium tuberculosis. Interestingly, changes in the same three codons of the consensus sequence occur repeatedly in unrelated RIF-resistant (RIFr) clinical isolates of several different bacterial species, and a single mutation predominates in mycobacteria. The utilization of our knowledge of these mutations to develop rapid screening tests for detecting resistance is briefly discussed. Cross-resistance among rifamycins has been a topic of controversy; current thinking is that there is no difference in the susceptibility of RNAP mutants to RIF, rifapentine and rifabutin. Also summarized are intrinsic RIF resistance and other resistance mechanisms.
268 citations
TL;DR: In this review, the discovery, development and associated resistance of vancomycin and teicoplanin, and semi-synthetic glycopeptides, telavancin (3), dalbavancein (4) and oritavancIn (5), are detailed and the clinical implications of glycopePTide resistance, as well as the future prospects for current glycopesptide drugs and the development of new glycopeptic drugs are discussed.
Abstract: Glycopeptide antibiotics have been a key weapon in the fight against bacterial infections for over half a century, with the progenitors, vancomycin (1) and teicoplanin (2), still used extensively. The increased occurrence of resistance and the effectiveness of these ‘last resort’ treatments for Gram-positive infections has led to the discovery and clinical development of second generation, semisynthetic lipoglycopeptide derivatives such as telavancin (3), dalbavancin (4) and oritavancin (5), which all possess broader spectra of activity and improved pharmacokinetic properties. Two of these new antibiotics, telavancin (3) and dalbavancin (4), were approved in the past 5 years and the third, oritavancin (5), is awaiting regulatory approval. In this review, the discovery, development and associated resistance of vancomycin (1) and teicoplanin (2), and semi-synthetic glycopeptides, telavancin (3), dalbavancin (4) and oritavancin (5), are detailed. The clinical implications of glycopeptide resistance, especially vancomycin (1), as well as the future prospects for current glycopeptide drugs and the development of new glycopeptides are discussed.
199 citations
TL;DR: It is suggested that the inhibition of vital respiratory enzymes in the bacterial inner membrane represents one of the secondary modes of action for polymyxins in response to ubiquinone-1 and NADH.
Abstract: Polymyxin B and colistin were examined for their ability to inhibit the type II NADH-quinone oxidoreductases (NDH-2) of three species of Gram-negative bacteria. Polymyxin B and colistin inhibited the NDH-2 activity in preparations from all of the isolates in a concentration-dependent manner. The mechanism of NDH-2 inhibition by polymyxin B was investigated in detail with Escherichia coli inner membrane preparations and conformed to a mixed inhibition model with respect to ubiquinone-1 and a non-competitive inhibition model with respect to NADH. These suggest that the inhibition of vital respiratory enzymes in the bacterial inner membrane represents one of the secondary modes of action for polymyxins.
157 citations
TL;DR: Recent advances in understanding of both biosynthesis and resistance of glycopeptide-resistant enterococci and other resistant bacteria are described.
Abstract: Glycopeptides such as vancomycin, teicoplanin and telavancin are essential for treating infections caused by Gram-positive bacteria. Unfortunately, the dwindled pipeline of new antibiotics into the market and the emergence of glycopeptide-resistant enterococci and other resistant bacteria are increasingly making effective antibiotic treatment difficult. We have now learned a great deal about how bacteria produce antibiotics. This information can be exploited to develop the next generation of antimicrobials. The biosynthesis of glycopeptides via nonribosomal peptide assembly and unusual amino acid synthesis, crosslinking and tailoring enzymes gives rise to intricate chemical structures that target the bacterial cell wall. This review seeks to describe recent advances in our understanding of both biosynthesis and resistance of these important antibiotics.
148 citations
TL;DR: Advances in the genetics and biochemistry of wall teichoic acid synthesis have led to a new understanding of the complexity of cell wall synthesis in Gram-positive bacteria and remarkable synthetic-viable interactions among biosynthetic genes have been leveraged for the discovery and characterization of novel inhibitors of the pathway.
Abstract: Wall teichoic acids are a major and integral component of the Gram-positive cell wall These structures are present across all species of Gram-positive bacteria and constitute roughly half of the cell wall Despite decades of careful investigation, a definitive physiological function for wall teichoic acids remains elusive Advances in the genetics and biochemistry of wall teichoic acid synthesis have led to a new understanding of the complexity of cell wall synthesis in Gram-positive bacteria Indeed, these innovations have provided new molecular tools available to probe the synthesis and function of these cell wall structures Among recent discoveries are unexpected roles for wall teichoic acid in cell division, coordination of peptidoglycan synthesis and β-lactam resistance in methicillin-resistant Staphylococcus aureus (MRSA) Notably, wall teichoic acid biogenesis has emerged as a bona fide drug target in S aureus, where remarkable synthetic-viable interactions among biosynthetic genes have been leveraged for the discovery and characterization of novel inhibitors of the pathway
94 citations
TL;DR: The analytical techniques of dereplication and related technologies in this review article are described and discussed so that the desired compound in the mixture library can be rapidly identified.
Abstract: Natural products still continue to have an important role as a resource of various biologically active substances. Dereplication is a key process in natural product screening that analyzes the extracts of microbial fermentation broths or plant samples. In this review article, we describe and discuss the analytical techniques of dereplication and related technologies in the following sections: 1. Direct detection from microbial colonies. 2. Ultra high performance liquid chromatography (UHPLC)-MS profiling for library construction. 3. Micro-fractionation to identify active peaks. 4. Quantification of small-amount compounds. 5. Structure identification from small amounts. Using these techniques, the desired compound in the mixture library can be rapidly identified.
77 citations
TL;DR: The multilateral symbioses common to insect agricultural systems, the general strategy used for antibiotic discovery and pertinent examples from three farming systems are described, including fungus-farming ants, southern pine beetles and fungus-growing termites.
Abstract: As increased antibiotic resistance erodes the efficacy of currently used drugs, the need for new candidates with therapeutic potential grows. Although the majority of antibiotics in clinical use originated from natural products, mostly from environmental actinomycetes, high rediscovery rates, among other factors, have diminished the enthusiasm for continued exploration of this historically important source. Several well-studied insect agricultural systems have bacterial symbionts that have evolved to produce small molecules that suppress environmental pathogens. These molecules represent an underexplored reservoir of potentially useful antibiotics. This report describes the multilateral symbioses common to insect agricultural systems, the general strategy used for antibiotic discovery and pertinent examples from three farming systems: fungus-farming ants, southern pine beetles (SPBs) and fungus-growing termites.
69 citations
TL;DR: A global visualization of the detectable molecules produced from a single microorganism, which is defined as the ‘molecular network’ of that organism, is described, followed by studies to characterize the cellular effects of antibacterial molecules.
Abstract: Most (75%) of the anti-infectives that save countless lives and enormously improve quality of life originate from microbes found in nature. Herein, we described a global visualization of the detectable molecules produced from a single microorganism, which we define as the ‘molecular network’ of that organism, followed by studies to characterize the cellular effects of antibacterial molecules. We demonstrate that Streptomyces roseosporus produces at least four non-ribosomal peptide synthetase-derived molecular families and their gene subnetworks (daptomycin, arylomycin, napsamycin and stenothricin) were identified with different modes of action. A number of previously unreported analogs involving truncation, glycosylation, hydrolysis and biosynthetic intermediates and/or shunt products were also captured and visualized by creation of a map through MS/MS networking. The diversity of antibacterial compounds produced by S. roseosporus highlights the importance of developing new approaches to characterize the molecular capacity of an organism in a more global manner. This allows one to more deeply interrogate the biosynthetic capacities of microorganisms with the goal to streamline the discovery pipeline for biotechnological applications in agriculture and medicine. This is a contribution to a special issue to honor Chris Walsh’s amazing career.
64 citations
TL;DR: Possible mechanisms for β-lactam activity in M. tuberculosis and the means by which it may acquire resistance, within the context of what is known in other bacterial species are discussed.
Abstract: β-Lactams are one of the most useful classes of antibiotics against many common bacterial pathogens. One exception is Mycobacterium tuberculosis. However, with increasing incidence of multidrug-resistant tuberculosis and a need for new agents to treat it, the use of β-lactams, specifically the combination of carbapenem and clavulanate, is now being revisited. With this attention, comes the need to better understand both the mechanisms of action of β-lactams against M. tuberculosis as well as possible mechanisms of resistance, within the context of what is known about the β-lactam action in other bacteria. M. tuberculosis has two major mechanisms of intrinsic resistance: a highly active β-lactamase and a poorly permeable outer membrane. Within the cell wall, β-lactams bind several enzymes with differing peptidoglycan-synthetic and -lytic functions. The inhibition of these enzymes may lead to cell death through several mechanisms, involving disruption of the balance of synthetic and lethal activities. Currently, all known means of resistance to the β-lactams rely on diminishing the proportion of peptidoglycan-synthetic proteins bound and inhibited by β-lactams, through either exclusion or destruction of the antibiotic, or through replacement or supplementation of target enzymes. In this review, we discuss possible mechanisms for β-lactam activity in M. tuberculosis and the means by which it may acquire resistance, within the context of what is known in other bacterial species.
61 citations
TL;DR: An automated method was developed to extract and consolidate all multimodular PKS sequences in the National Center for Biotechnology Information database, generating a non-redundant catalog of 885 distinct assembly-line PKSs, the majority of which were orphans associated with no known polyketide product.
Abstract: The increasing availability of DNA sequence data offers an opportunity for identifying new assembly-line polyketide synthases (PKSs) that produce biologically active natural products. We developed an automated method to extract and consolidate all multimodular PKS sequences (including hybrid PKS/non-ribosomal peptide synthetases) in the National Center for Biotechnology Information (NCBI) database, generating a non-redundant catalog of 885 distinct assembly-line PKSs, the majority of which were orphans associated with no known polyketide product. Two in silico experiments highlight the value of this search method and resulting catalog. First, we identified an orphan that could be engineered to produce an analog of albocycline, an interesting antibiotic whose gene cluster has not yet been sequenced. Second, we identified and analyzed a hitherto overlooked family of metazoan multimodular PKSs, including one from Caenorhabditis elegans. We also developed a comparative analysis method that identified sequence relationships among known and orphan PKSs. As expected, PKS sequences clustered according to structural similarities between their polyketide products. The utility of this method was illustrated by highlighting an interesting orphan from the genus Burkholderia that has no close relatives. Our search method and catalog provide a community resource for the discovery of new families of assembly-line PKSs and their antibiotic products.
ALFA1
TL;DR: This review updates the pharmacology and pharmacodynamics of rifaximin highlighting the different actions, beyond its antibacterial activity, such as alteration of virulence, prevention of gut mucosal adherence and bacterial translocation.
Abstract: Rifaximin is a non-systemic oral antibiotic derived from rifampin and characterized by a broad spectrum of antibacterial activity against Gram-positive and -negative, aerobic and anaerobic bacteria. Rifaximin was first approved in Italy in 1987 and afterwards in many other worldwide countries for the treatment of several gastrointestinal diseases. This review updates the pharmacology and pharmacodynamics of rifaximin highlighting the different actions, beyond its antibacterial activity, such as alteration of virulence, prevention of gut mucosal adherence and bacterial translocation. Moreover, rifaximin exerts some anti-inflammatory effects with only a minimal effect on the overall composition of the gut microbiota. All these properties make rifaximin a good candidate to treat various gastrointestinal diseases.
TL;DR: An additional visualization step for the molecular networking workflow is developed to provide relative and absolute quantitation of a specific compound in an extract to identify and quantitatively compare several producers of the bioactive and biosynthetically intriguing lipopeptide malyngamide C.
Abstract: Untargeted liquid chromatography-MS (LC-MS) is used to rapidly profile crude natural product (NP) extracts; however, the quantity of data produced can become difficult to manage. Molecular networking based on MS/MS data visualizes these complex data sets to aid their initial interpretation. Here, we developed an additional visualization step for the molecular networking workflow to provide relative and absolute quantitation of a specific compound in an extract. The new visualization also facilitates combination of several metabolomes into one network, and so was applied to an MS/MS data set from 20 crude extracts of cultured marine cyanobacteria. The resultant network illustrates the high chemical diversity present among marine cyanobacteria. It is also a powerful tool for locating producers of specific metabolites. In order to dereplicate and identify culture-based sources of known compounds, we added MS/MS data from 60 pure NPs and NP analogs to the 20-strain network. This dereplicated six metabolites directly and offered structural information on up to 30 more. Most notably, our visualization technique allowed us to identify and quantitatively compare several producers of the bioactive and biosynthetically intriguing lipopeptide malyngamide C. Our most prolific producer, a Panamanian strain of Okeania hirsuta (PAB10FEB10-01), was found to produce at least 0.024 mg of malyngamide C per mg biomass (2.4%, w/dw) and is now undergoing genome sequencing to access the corresponding biosynthetic machinery.
TL;DR: This research presents a probabilistic procedure to estimate the polymethine content of the response of the H2O/O2 mixture through a number of different experimental procedures, including “situ-based,” “chemical-based” and “novel” methods.
Abstract: National Key Basic Research Program of China (973)'s Project [2010CB833800, 2011CB915503]; Open Foundation of the Key Lab of Marine Bioactive Substance and Modern Analytical Technique, SOA [MBSMAT-2013-02]; National High Technology Research and Development Program (863 Program) [2013AA092901, 2012AA092104]; National Natural Science Foundation of China [31270402, 21172230, 20902094, 41176148, 21002110]; Guangdong Province-CAS Joint Research Program [20118090300023, 20128091100264]; Guangdong Marine Economic Development and Innovation of Regional Demonstration Project [GD2012-D01-001, GD2012-D01-002]
TL;DR: This review will discuss the techniques and strategies that have been applied to determine the primary structures of lantibiotics and sactibiotics, a group of ribosomally synthesized antimicrobial peptides produced by bacteria that are extensively post-translationally modified.
Abstract: Bacteriocins are a group of ribosomally synthesized antimicrobial peptides produced by bacteria, some of which are extensively post-translationally modified. Some bacteriocins, namely the lantibiotics and sactibiotics, contain one or more thioether bridges. However, these modifications complicate the structural elucidation of these bacteriocins using conventional techniques. This review will discuss the techniques and strategies that have been applied to determine the primary structures of lantibiotics and sactibiotics. A major challenge is to identify the topology of thioether bridges in these peptides (i.e., which amino-acid residues are involved in which bridges). Edman degradation, NMR spectroscopy and tandem MS have all been commonly applied to characterize these bacteriocins, but can be incompatible with the post-translational modifications present. Chemical modifications to the modified residues, such as desulfurization and reduction, make the treated bacteriocins more compatible to analysis by these standard peptide analytical techniques. Despite their differences in structure, similar strategies have proved useful to study the structures of both lantibiotics and sactibiotics.
TL;DR: Two new rubrolides, rubrolide R (1) and S (2), were isolated from the fermentation broth of the marine-derived fungus Aspergillus terreus OUCMDZ-1925 and showed comparable or superior anti-influenza A (H1N1) virus activity to that of ribavirin with an IC50 value of 87.1 μM.
Abstract: Two new rubrolides, rubrolides R (1) and S (2), were isolated from the fermentation broth of the marine-derived fungus Aspergillus terreus OUCMDZ-1925. Their structures were elucidated on the basis of spectroscopic analysis and X-ray single crystal diffraction. Compound 1 showed comparable or superior antioxidation against 2,2′-azino-di(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radicals to those of trolox and ascorbic acid with an IC50 value of 1.33 mM. Compound 2 showed comparable or superior anti-influenza A (H1N1) virus activity to that of ribavirin with an IC50 value of 87.1 μM. Both compounds 1 and 2 showed weak cytotoxicity against the K562 cell line with IC50 values of 12.8 and 10.9 μM, respectively.
Journal Article•
TL;DR: Bacteria isolated from surgical infections during the period from April 2010 to March 2011 were investigated in a multicenter study in Japan, and the following results were obtained.
Abstract: This is an integrated summary of the results obtained from a 3-decade multicenter study on bacteria isolated from surgical infections in Japan between July 1982 and March 2012. During the 3-decade study, 11,196 strains were isolated from 4,787 patients consisting of 2,132 patients with primary infection and 2,655 patients with surgical site infection. Almost half of the primary infection was peritonitis, which accounted for 42.3%-55.5%. In contrast, most of the surgical site infection was wound infection, which accounted for 49.3%-66.1%. The most commonly isolated bacteria throughout three decades were Escherichia coli (1,164 strains), Enterococcus faecalis (842), Staphylococcus aureus (833), Pseudomonas aeruginosa (706), Bacteroides fragilis (705), Klebsiella pneumoniae (498), Enterobacter cloacae (391) and coagulase-negative staphylococci (CNS) (325). Overall, S. aureus and CNS had sensitivity for vancomycin, whose MIC90s were 0.78 to 3.13 μg/mL; E. faecalis had sensitivity for vancomycin and imipenem, whose MIC90s were 0.78-4 μg/mL; E coli, E. cloacae, K. pneumoniae, and B. fragilis had preferable sensitivity for imipenem. No antibacterial agents had a long-term good activity (e.g. MIC90 < 2 μg/mL) for P aeruginosa and Bilophila wadsworthia. Among antibacterial agents tested, ciprofloxacin had most bactericidal activity for P. aeruginosa; its MIC90 varied from 0.5 to 8 μg/mL. The MIC90s of all antibacterial agents tested except levofloxacin and minocycline were at least 128 μg/mL for B. wadsworthia. S. aureus accounted for approximately 20% to 60% of bacteria isolated after clean operation. Overall, at least 55% of the bacteria isolated after clean operation consisted of S. aureus, CNS, E. faecalis, E. coli, E. cloacae, K. pneunoniae, P. aeruginosa, B. fragilis, and B. wadsworthia throughout three decades. However, the percentage of other Gram-positive and negative bacteria increased with the worse of sterile condition in surgical operation. E. faecalis tended to be most commonly isolated from patients having host-compromised factors including carcinoma, diabetes, anticancer agents, steroids, immunosuppressants, and radiation, while E. coli was commonly isolated from patients having no such factors. Two-drug-resistant P. aeruginosa was first isolated in 1987, thereafter was frequently isolated, and reached 69 strains for 30 years. Three-drug-resistant P. aeruginosa was isolated in 1990, 1996, and 1998 to reach 5 strains, but not isolated in remaining 13 years. Methicillin-resistant S. aureus was highly frequently isolated between 1988 and 1991. Subsequently, the isolation frequency declined, sometimes increased in 1998, 2005, and 2006, and thereafter maintained lower levels by 2011.
TL;DR: Two Trp-substituted AMPs designed by replacing Ile or Leu residues with two Trp residues at different positions in the L-K6 peptide exhibited significantly higher antimicrobial activity and lower cytotoxicity against Gram-negative and Gram-positive bacteria compared with L- K6.
Abstract: Tryptophan (Trp) residues reportedly exhibit a strong membrane-disruptive activity, and this property endows Trp-containing antimicrobial peptides (AMPs) with a unique ability to interact with the surface of bacterial cell membranes, possibly improving antimicrobial properties. In this study, we investigated the influence of Trp residues engineered to have a distinct preference for the interface region of lipid bilayers on antimicrobial activity. We designed two Trp-substituted AMPs (I1WL5W and I4WL5W) by replacing Ile or Leu residues with two Trp residues at different positions in the L-K6 peptide, and determined their antimicrobial activity and mechanism of membrane action. Both I1WL5W and I4WL5W exhibited significantly higher antimicrobial activity and lower cytotoxicity against Gram-negative and Gram-positive bacteria compared with L-K6. The Trp-substituted peptides had a disordered structure in aqueous solution and adopted an α-helical structure in solutions of 50% trifluoroethanol/water and 30 mM SDS. I1WL5W and I4WL5W caused a significant leakage of calcein from liposomes containing membranes that mimicked those of Escherichia coli and Staphylococcus aureus. Scanning electron microscopy analysis suggested that I1WL5W and I4WL5W killed bacteria by disrupting bacterial cell membranes. Furthermore, fluorescence and quenching data from a variety of liposomes, which mimic different cell membranes, indicated that the Trp-substituted peptides could insert into the lipid bilayers and induce blue shifts in the emission spectra of the Trp residues. I1WL5W and I4WL5W were also less susceptible to acrylamide or KI quenchers. The current work may be important for designing novel Trp-containing peptides exhibiting strong antimicrobial abilities by penetrating bacterial membranes.
TL;DR: Two new diterpenes were isolated from the fungus Eutypella sp.
Abstract: Two new diterpenes, libertellenone G(1) and libertellenone H(2) were isolated from the fungus Eutypella sp. D-1 isolated from the soil of high latitude of Arctic, together with two known pimarane diterpenes (3–4). The structures of 1 and 2 were elucidated from spectroscopic data (nuclear magnetic resonance, mass spectrometry and infrared). These compounds were evaluated for cytotoxic activity against seven human tumor cell lines. Compound 2 showed a range of cytotoxicity between 3.31 and 44.1 μM. Compound 1 exhibited antibacterial activity against Escherichia coli, Bacillus subtilis and Staphylococcus aureus.
TL;DR: In this review, a few of new antitubercular molecules appeared on the horizon both in preclinical and clinical stage of evaluation and on their mechanism of action are focused on.
Abstract: After the introduction of isoniazid and rifampicin, the second one discovered in the Lepetit Research Laboratories (Milan, Italy), under the supervision of Professor Piero Sensi, tuberculosis (TB) was considered an illness of the past. Unfortunately, this infectious disease is still a global health fear, due to the multidrug-resistant Mycobacterium tuberculosis and extensively circulating drug-resistant strains, as well as the unrecognized TB transmission, especially in regions with high HIV incidence. In the last few years, new antitubercular molecules appeared on the horizon both in preclinical and clinical stage of evaluation. In this review, we focus on a few of them and on their mechanism of action. Two new promising drug targets, DprE1 and MmpL3, are also discussed.
TL;DR: Potential options in situations where the catheter cannot be removed include the combination of systemic and lock antifungal therapy and well-designed and -executed clinical trials must be performed before firm recommendations can be issued.
Abstract: Catheter-related bloodstream infection (C-RBSI) is one of the most frequent nosocomial infections It is associated with high rates of morbidity and mortality Candida spp is the third most common cause of C-RBSI after coagulase-negative staphylococci and Staphylococcus aureus and is responsible for approximately 8% of episodes The main cause of catheter-related candidemia is the ability of some Candida strains—mainly C albicans and C parapsilosis—to produce biofilms Many in vitro and in vivo models have been designed to assess the activity of antifungal drugs against Candida biofilms Echinocandins have proven to be the most active antifungal drugs Potential options in situations where the catheter cannot be removed include the combination of systemic and lock antifungal therapy However, well-designed and -executed clinical trials must be performed before firm recommendations can be issued
TL;DR: It is suggested that A2-type cranberry proanthocyanidins could aid in maintaining urinary tract health by preventing adhesion of P-fimbriated UPEC to uroepithelial cells.
Abstract: Urinary tract infections (UTIs) are relatively common in women and may be classified as uncomplicated or complicated, depending upon the urinary tract anatomy and physiology. Acute uncomplicated cystitis (AUC) occurs when urinary pathogens from the bowel or vagina colonize the periurethral mucosa and reach the bladder. The vast majority of episodes in healthy women involving the same bacterial strain that caused the initial infection are thought to be reinfections. About 90% of AUC are caused by uropathogenic Escherichia coli (UPEC), but Proteus mirabilis also plays an important role. Several studies support the importance of cranberry (Vaccinium macrocarpon) proanthocyanidins in preventing adhesion of P-fimbriated UPEC to uroepithelial cells. In this study, we evaluated the in vitro anti-adhesion activity of A2-linked proanthocyanidins from cranberry on a UPEC and Proteus mirabilis strains and their possible influence on urease activity of the latter. A significant reduction of UPEC adhesion (up to 75%) on the HT1376 cell line was observed vs. control. For the strains of P. mirabilis there was also a reduction of adhesion (up to 75%) compared to controls, as well as a reduction in motility and urease activity. These results suggest that A2-type cranberry proanthocyanidins could aid in maintaining urinary tract health.
TL;DR: A novel depsipeptide was purified from an endophytic fungus Phomopsis glabrae isolated from the leaves of Pongamia pinnata and exhibited in vitro anticancer activity against 40 human cancer cell lines and ex vivo efficacy towards 24 human tumor xenografts.
Abstract: A novel depsipeptide (PM181110) was purified from an endophytic fungus Phomopsis glabrae isolated from the leaves of Pongamia pinnata (family Fabaceae). The chemical structure of PM181110 was elucidated using physiochemical properties, 2D NMR and other spectroscopic methods. PM181110 is very close in structure to FE399. The compound exhibited in vitro anticancer activity against 40 human cancer cell lines with a mean IC50 value of 0.089 μM and ex vivo efficacy towards 24 human tumor xenografts (mean IC50=0.245 μM).
TL;DR: Another natural product is reported that functions as a SUMOylation inhibitor: davidiin, purified from the plant Davidia involucrata, which is particularly potent, inhibiting at sub-micromolar concentrations.
Abstract: Conjugation of small ubiquitin-related modifier (SUMO) to lysine residues in target proteins is a multistep enzymatic reaction analogous to ubiquitination.1 Protein SUMOylation regulates numerous biological processes including transcription, the cell cycle, DNA repair and innate immunity.1 In the first step of the reaction, SUMO is cleaved from the SUMO precursor by SUMO-specific proteases. Next, SUMO is bound to the cysteine residue of the SUMO-activating enzyme (E1), forming a thioester linkage in an ATP-dependent manner. SUMO is then transferred from E1 to the cysteine residue of the SUMO-conjugating enzyme (E2). Finally, SUMO ligase (E3) catalyzes the SUMOylation of specific substrates via a direct interaction with E2 and the substrates. Like ubiquitination, SUMOylation is reversible; the deSUMOylation process is mediated by SUMO-specific proteases. Abnormal SUMOylation is implicated in various diseases including neurodegenerative disease,2 viral infection3 and cancer.4,5 Therefore, enzymes responsible for the SUMO conjugation pathway represent potential targets for drug discovery. To date, several natural products including ginkgolic acid,6 anacardic acid,6 kerriamycin B7 and spectomycin B18 as well as synthetic compounds,9 have been reported to inhibit protein SUMOylation. Here, we report another natural product that functions as a SUMOylation inhibitor: davidiin, purified from the plant Davidia involucrata. Although most known SUMOylation inhibitors function in the micromolar range, davidiin is particularly potent, inhibiting at sub-micromolar concentrations. Materials for this study were obtained as follows. Goat polyclonal anti-SUMO-1 (N-19) and goat polyclonal anti-p53 (FL393)-G antibodies were purchased from Santa Cruz Biotechnologies (Santa Cruz, CA, USA). A mouse monoclonal anti-T7 antibody was from Novagen (Darmstadt, Germany). Mouse monoclonal anti-a-tubulin (B-5-1-2) and anti-FLAG (M2) antibodies were purchased from Sigma (St. Louis, MO, USA). Recombinant Hisand T7-tagged RanGAP1-C2, GST-Aos1-Uba2 fusion protein (E1), His-tagged Ubc9 (E2), and Histagged SUMO-1 proteins were purified as described previously.10 293T, H1299, MKN-45, DU-145 and NCI-H460 cells were maintained in Dulbecco’s modified Eagle medium supplemented with 10% FBS at 37 1C under 5% CO2. The in vitro SUMOylation reaction was performed as described.6 Briefly, in vitro SUMOylation reaction was performed for 2 h at 30 1C in 20ml buffer (50 mM Tris-HCl (pH 7.4), 6 mM MgCl2, 2 mM ATP and 1 mM dithiothreitol) containing Hisand T7-tagged RanGAP1-C2, GST-Aos1/Uba2 (E1), His-tagged Ubc9 and His-tagged SUMO-1. Samples were separated by 10% SDS–PAGE followed by immunoblotting using an anti-T7 antibody and an anti-SUMO-1 antibody. The reaction for thioester bond formation between SUMO and E1 was performed as described.6 Briefly, the reaction for the thioester bond formation was performed for 20 min at 37 1C in 20ml buffer (50 mM Tris-HCl (pH 7.4), 6 mM MgCl2, 2 mM ATP) containing GSTAos1/Uba2 (E1) and biotinylated SUMO-1 in the absence of dithiothreitol. Samples were separated by 11% SDS–PAGE and the E1–biotinylated SUMO-1 intermediate was detected by avidin-conjugated horseradish peroxidase (Sigma). A screen of 750 samples of botanical and food ingredients extracts using an in situ cell-based SUMOylation assay11 revealed several samples that could inhibit protein SUMOylation, including an extract of D. involucrata (data not shown).6 The inhibitory activity of the D. involucrata extract was confirmed by in vitro SUMOylation assay using RanGAP1-C2 as substrate (Figure 1a). Compound A was isolated by activity-guided fractionation and it was identified by
TL;DR: Two new cyclopentadecane antibiotics, named mangromicins A and B, were separated out from the culture broth of Lechevalieria aerocolonigenes K10-0216 by Diaion HP-20, silica gel and ODS column chromatography, and were finally purified by HPLC.
Abstract: Two new cyclopentadecane antibiotics, named mangromicins A and B, were separated out from the culture broth of Lechevalieria aerocolonigenes K10-0216 by Diaion HP-20, silica gel and ODS column chromatography, and were finally purified by HPLC. The chemical structures of the two novel compounds were elucidated by instrumental analyses, including various NMR, MS and X-ray crystallography. Mangromicins A and B consist of cyclopentadecane skeletons with a tetrahydrofuran unit and a 5,6-dihydro-4-hydroxy-2-pyrone moiety. Mangromicins A and B showed in vitro antitrypanosomal activity with IC50 values of 2.4 and 43.4 μg ml−1, respectively. The IC50 values of both compounds were lower than those of cytotoxicity against MRC-5 human fetal lung fibroblast cells.
TL;DR: The results suggest a mechanism of action involving inhibition of DXP synthase and show that BAP acts synergistically with established antimicrobial agents, highlighting a potential strategy to combat emerging resistance in bacterial pathogens.
Abstract: The unique methylerythritol phosphate pathway for isoprenoid biosynthesis is essential in most bacterial pathogens. The first enzyme in this pathway, 1-deoxy-D-xylulose 5-phosphate (DXP) synthase, catalyzes a distinct thiamin diphosphate (ThDP)-dependent reaction to form DXP from D-glyceraldehyde 3-phosphate (D-GAP) and pyruvate and represents a potential anti-infective drug target. We have previously demonstrated that the unnatural bisubstrate analog, butylacetylphosphonate (BAP), exhibits selective inhibition of Escherichia coli DXP synthase over mammalian ThDP-dependent enzymes. Here, we report the selective inhibition by BAP against recombinant DXP synthase homologs from Mycobacterium tuberculosis, Yersinia pestis and Salmonella enterica. We also demonstrate antimicrobial activity of BAP against both Gram-negative and Gram-positive strains (including E. coli, S. enterica and Bacillus anthracis), and several clinically isolated pathogens. Our results suggest a mechanism of action involving inhibition of DXP synthase and show that BAP acts synergistically with established antimicrobial agents, highlighting a potential strategy to combat emerging resistance in bacterial pathogens.
TL;DR: Knowing of antimicrobial resistance data and virulence factors may enable clinicians to tailor empirical antibiotic treatments for UTIs.
Abstract: Uropathogenic Escherichia coli (UPEC) is the major cause of urinary tract infections (UTIs). In the present study, 198 E. coli isolates from patients with UTIs in Shanghai in 2008 were examined by susceptibility testing, with an extremely high number (153/198) showing multidrug resistance (MDR). And, the expression of extended-spectrum β-lactamases (ESBLs) reached 48.5% (96/198). The resistance rates to penicillins, fluoroquinolone, folate pathway inhibitors and first- and second-generation cephalosporins were high. Molecular analyses showed that the CTX-M-9 group (70/96) was the most common CTX-M group among UPEC, followed by the CTX-M-1 group (27/96). Phylogenetic group D accounted for 42.4% (84/198) of the isolates, exhibiting the highest ESBLs (50/84) and MDR (75/84) rates. Virulence genes were present in a significantly high proportion in the phylogenetic group B2 isolates, except for the afaBC gene. The ESBL-producing strains analyzed by pulsed-field gel electrophoresis (PFGE) were clustered into six groups at a cutoff of 67%. Notably, the findings that afaBC was specific to phylogenetic group D and PFGE group I and was correlated with the CTX-M-9 group were different from a previous report. In conclusion, knowledge of antimicrobial resistance data and virulence factors may enable clinicians to tailor empirical antibiotic treatments for UTIs.
TL;DR: Although its postantibiotic effects were minimal, anthracimycin exhibited potent and rapid bactericidal activity, with a >4-log kill of USA300 MRSA within 3 h at five times its MIC.
Abstract: Anthracimycin is a recently discovered novel marine-derived compound with activity against Bacillus anthracis. We tested anthracimycin against an expanded panel of Staphylococcus aureus strains in vitro and in vivo. All strains of S. aureus tested, including methicillin-susceptible, methicillin-resistant (MRSA) and vancomycin-resistant strains of S. aureus, were susceptible to anthracimycin at MIC values of ⩽0.25 mg l(-1). Although its postantibiotic effects were minimal, anthracimycin exhibited potent and rapid bactericidal activity, with a >4-log kill of USA300 MRSA within 3 h at five times its MIC. At concentrations significantly below the MIC, anthracimycin slowed MRSA growth and potentiated the bactericidal activity of the human cathelicidin, LL-37. The bactericidal activity of anthracimycin was somewhat mitigated in the presence of 20% human serum, and the compound was minimally toxic to human cells, with an IC50 (inhibitory concentration 50)=70 mg l(-1) against human carcinoma cells. At concentrations near the MIC, anthracimycin inhibited S. aureus nucleic acid synthesis as determined by optimized macromolecular synthesis methodology, with inhibition of DNA and RNA synthesis occurring in the absence of DNA intercalation. Anthracimycin at a single dose of 1 or 10 mg kg(-1) was able to protect mice from MRSA-induced mortality in a murine peritonitis model of infection. Anthracimycin provides an interesting new scaffold for future development of a novel MRSA antibiotic.
TL;DR: Five alkenyl phenol and benzaldehyde derivatives, pestalols A-E, as well as seven known compounds, were isolated from endophytic fungus Pestalotiopsis sp.
Abstract: Five alkenyl phenol and benzaldehyde derivatives, pestalols A-E (1-5), as well as seven known compounds (6-12), were isolated from endophytic fungus Pestalotiopsis sp. AcBC2 derived from the Chinese mangrove plant Aegiceras corniculatum. Their structures were determined by spectroscopic analyses. Compounds 2 and 3 showed cytotoxicity against a panel of 10 tumor cell lines. Compounds 1-5, 8, 9, 11, and 12 showed inhibitory activities against Influenza A virus subtype (H3N2) and Swine Flu (H1N1) viruses. Compound 2 also showed inhibitory activity against tuberculosis.
TL;DR: A new 20-membered macrolide along with the known venturicidins A–C did not inhibit the proliferation of A549 lung cancer cell line but all displayed potent antifungal activity.
Abstract: Venturicidin C (1), a new 20-membered macrolide along with the known venturicidins A (2) and B (3) were isolated from the crude extract of the Appalachian bacterial strain Streptomyces sp. TS-2-2. Additionally, nine other known compounds namely nocardamine, dehydroxynocardamine, desmethylenylnocardamine, ferrioxamine E, adenosine, riboflavin, cyclo(D)-trans-4-OH-Pro-(D)-Phe, cyclo(D)-Pro-(D)-Phe and N-(2-phenylethyl)-acetamide were also isolated and identified. The structure of the new macrolide 1 was elucidated by the cumulative analyses of NMR spectroscopy and HR-MS data. Complete NMR assignments for the known venturicidins A (2) and B (3) are also provided, for the first time, in this report. Venturicidins A–C did not inhibit the proliferation of A549 lung cancer cell line but all displayed potent antifungal activity.