Bacterioferritin: a key iron storage modulator that affects strain growth and butenyl-spinosyn biosynthesis in Saccharopolyspora pogona.

BACKGROUND: Butenyl-spinosyn, produced by Saccharopolyspora pogona, is a promising biopesticide due to excellent insecticidal activity and broad pesticidal spectrum. Bacterioferritin (Bfr, encoded by bfr) regulates the storage and utilization of iron, which is essential for the growth and metabolism of microorganisms. However, the effect of Bfr on the growth and butenyl-spinosyn biosynthesis in S. pogona has not been explored. RESULTS: Here, we found that the storage of intracellular iron influenced butenyl-spinosyn biosynthesis and the stress resistance of S. pogona, which was regulated by Bfr. The overexpression of bfr increased the production of butenyl-spinosyn by 3.14-fold and enhanced the tolerance of S. pogona to iron toxicity and oxidative damage, while the knockout of bfr had the opposite effects. Based on the quantitative proteomics analysis and experimental verification, the inner mechanism of these phenomena was explored. Overexpression of bfr enhanced the iron storage capacity of the strain, which activated polyketide synthase genes and enhanced the supply of acyl-CoA precursors to improve butenyl-spinosyn biosynthesis. In addition, it induced the oxidative stress response to improve the stress resistance of S. pogona. CONCLUSION: Our work reveals the role of Bfr in increasing the yield of butenyl-spinosyn and enhancing the stress resistance of S. pogona, and provides insights into its enhancement on secondary metabolism, which provides a reference for optimizing the production of secondary metabolites in actinomycetes.

In vitro activity of cefditoren versus other antibiotics against S. pneumoniae clinical strains isolated in Italy.

Over the last twenty years there has been an alarming increase in isolation of Streptococcus pneumoniae strains with a reduced susceptibility not only to penicillin, but also to other betalactams and macrolides. This phenomenon justifies the great interest in new antibiotics. Cefditoren, a new aminothiazolyl oral cephalosporin, recently commercialized in Italy, is characterized by an extended activity against penicillin-resistant S. pneumoniae. The aim of this study is to evaluate the incidence of the resistance/susceptibility to various antibiotics in 1000 strains of S. pneumoniae (678 SPSS, 219 SPPI and 103 SPPR), clinically isolated during 2009. The data obtained by our in vitro study show that cefditoren is the most active agent against S. pneumoniae. In fact, the MIC90 values of 0.5 micrograms/ml obtained could be particularly significant in therms of therapeutic predictivity.

MapsiDB: an integrated web database for type I polyketide synthases.

Polyketides have diverse biological activities, including pharmacological functions such as antibiotic, antitumor and agrochemical properties. They are biosynthesized from short carboxylic acid precursors by polyketide synthases (PKSs). As natural polyketide products include many clinically important drugs and the volume of data on polyketides is rapidly increasing, the development of a database system to manage polyketide data is essential. MapsiDB is an integrated web database formulated to contain data on type I polyketides and their PKSs, including domain and module composition and related genome information. Data on polyketides were collected from journals and online resources and processed with analysis programs. Web interfaces were utilized to construct and to access this database, allowing polyketide researchers to add their data to this database and to use it easily.

Synthesis of 3,6-bicyclolides: a novel class of macrolide antibiotics.

The synthesis of 3,6-bicyclolides from erythromycin A oxime is described. This novel class of bridged bicyclic macrolides demonstrates potent in vitro and in vivo activities against a broad spectrum of bacteria including resistant respiratory tract pathogens.

[Types and characteristics of macrolides]. / Podzial i charakterystyka makrolidów.

Macrolide antibiotics have been used to treat acute and chronic inflammation in the respiratory tract based on their antibacterial activity. Now it is well known that macrolides down-regulate damaging prolonged inflammation as well as increase mucus clearance and decrease bacterial virulence. Some drug interactions with macrolides have been documented in clinical trials mainly connected with their influence on liver function. Adverse reactions are few and self-limited when used at the recommended dosage.

Cruentaren A, a highly cytotoxic benzolactone from Myxobacteria is a novel selective inhibitor of mitochondrial F1-ATPases.

Cruentaren A, a new antifungal benzolactone produced by the myxobacterium Byssovorax cruenta, proved to be highly cytotoxic against various human cell lines. It inhibited the proliferation of different cancer cell lines including a multidrug-resistant KB line at low nanomolar levels. It arrested human histocytic lymphoma cells (U-937) in G(0/1) phase, but did not trigger an apoptotic process. Studies to uncover the molecular target of cruentaren A showed that the novel compound, despite its structural similarity to the benzolactone enamides apicularen and salicylihalamide, was no V-ATPase inhibitor. In contrast, cruentaren specifically inhibited mitochondrial F(O)F(1)-ATPases with IC50 values of 15-30 nM. Although the exact binding site of cruentaren remains undefined, inhibition was shown to occur by interaction with the catalytic F(1) domain. Since mitochondrial ATPases play a crucial role in the pathophysiology of several human disorders including cancer, cruentaren or synthetic derivatives thereof could form the basis of future therapeutic strategies.

Comparison of first-line with second-line antibiotics for acute exacerbations of chronic bronchitis: a metaanalysis of randomized controlled trials.

BACKGROUND: Although acute exacerbations of chronic bronchitis (AECBs) are common, there has been no metaanalysis that focused on the optimum regimen. METHODS: To evaluate the comparative effectiveness and safety of first-line antimicrobial agents (ie, amoxicillin, ampicillin, pivampicillin, trimethoprim/sulfamethoxazole, and doxycycline) and second-line antimicrobial agents (ie, amoxicillin/clavulanic acid, macrolides, second-generation or third-generation cephalosporins, and quinolones) for the treatment of patients with AECB, in an era of increasing antimicrobial resistance among the microbes responsible for AECB, we performed a metaanalysis of randomized controlled trials (RCTs) retrieved through searches of the PubMed and the Cochrane databases. RESULTS: Twelve RCTs were included in the metaanalysis. First-line antibiotics were associated with lower treatment success compared to second-line antibiotics in the clinically evaluable patients (odds ratio [OR], 0.51; 95% confidence interval [CI], 0.34 to 0.75). There were no differences among the compared regimens regarding mortality (OR, 0.64; 95% CI, 0.25 to 1.66) or treatment success (OR, 0.56; 95% CI, 0.22 to 1.43) in microbiologically evaluable patients, or adverse effects in general (OR, 0.75; 95% CI, 0.39 to 1.45) or diarrhea in particular (OR, 1.58; 95% CI, 0.74 to 3.35). CONCLUSIONS: Compared to first-line antibiotics, second-line antibiotics are more effective, but not less safe, when administered to patients with AECB. The available data did not allow for stratified analyses according to the presence of risk factors for poor outcome, such as increased age, impaired lung function, airway obstruction, and frequency of exacerbations; this fact should be taken into consideration when interpreting the findings of this metaanalysis.

In vitro activity of linezolid and 12 other antimicrobials against coryneform bacteria.

OBJECTIVES: To compare the in vitro activity of linezolid with 12 other antimicrobials against 190 strains of the coryneform bacteria, including 60 strains of C. amycolatum, 30 of C. striatum, 30 of C. jeikeium, 10 of C. urealyticum, 20 of B. casei, 20 of D. hominis and 20 of T. otitidis. METHODS: Minimum inhibitory concentrations (MICs) and time-death curves were carried out according to the recommendations of the Clinical and Laboratory Standards Institute (CLSI). RESULTS: Linezolid was very active against the 130 strains of the Corynebacterium species studied. Only the glycopeptides showed similar efficacy. In contrast, penicillin G, ampicillin, macrolides, lincosamides, fluoroquinolones and aminoglycosides showed generally high MICs. Among the beta-lactams, only imipenem was active against the majority of strains of C. striatum and C. amycolatum, and, approximately half of the C. jeikeium and C. urealyticum isolates. Both Dermabacter hominis and Brevibacterium casei showed marked resistance against most of the antimicrobials tested, while Turicella otitidis only showed high MICs against macrolides and clindamycin. For all of them, linezolid, vancomycin and teicoplanin proved effective. The time-death curves showed linezolid to behave as a bacteriostatic agent (approximately 90% death rate). Such activity was more accentuated for C. amycolatum and C. striatum (reduction of 1.3 and 1.7log(10)CFU/mL, respectively) than for C. jeikeium and C. urealyticum (reduction of 1.0 and 0.8log(10), respectively). CONCLUSIONS: Our results indicate that linezolid is active against coryneform bacteria. The efficacy of linezolid is equal to or even superior to that of the glycopeptides.

A tailoring activity is responsible for generating polyene amide derivatives in Streptomyces diastaticus var. 108.

We recently characterized rimocidin B (3b) and CE-108B (4b) as two polyene amides with improved pharmacological properties, produced by genetically modified Streptomyces diastaticus var. 108. In this work, genetic and biochemical analysis of the producer strain show that the two amides are derived from the parental polyenes rimocidin (3a) and CE-108 (4a) by a post-PKS modification of the free side chain carboxylic acid. This modification is mediated by an amidotransferase activity operating after the biosynthesis of rimocidin (3a) and CE-108 (4a) are completed. Two polyenes, intermediates of the biosynthetic pathway of rimocidin (3a) and CE-108 (4a), were also isolated and shown to have some improved pharmacological properties compared with the final products.

Effects of macrolides and ketolides on mycobacterial infections.

New macrolides, such as clarithromycin and azithromycin, are active agents to Mycobacterium avium complex (MAC). Both clarithromycin and azithromycin are well-known for the ability to improve the prognosis of AIDS patients with disseminated MAC infection. However, the administration of monotherapy with a macrolide is usually associated with the emergence of drug resistance after a few months of use. Therefore, the recommended treatment for MAC infection involved the use of at least two antibiotics, which includes a macrolide in combination with rifabutin, moxifloxacin and/or ethambutol. When used as prophylactic therapy in AIDS patients, azithromycin is more convenient (1200 mg, once a week) than clarithromycin (500 mg, twice a day). Ketolides are a semi-synthetic derivative of erythromycin A, which differs from erythromycin A by substitution of a 3-keto group for L-cladinose. Telithromycin has a carbamate group linked to an imidazolium and pyridium nucleus at C11-C12. In mice model, both telithromycin and ABT-733 were active in vivo against MAC.

Cellular and molecular effects of macrolides on leukocyte function.

Macrolide antimicrobials have stimulated worldwide interest owing to their therapeutic effects in various inflammatory, apparently non infectious, diseases. Abundant data are now available on their interactions with host cell (specially phagocyte) functions. Modulation of oxidant production by neutrophils and of pro-inflammatory cytokine synthesis and release by leukocytes are the two main effects observed in vitro. However, despite an extensive literature, many questions remain, such as the cellular/microbial target(s) of macrolide action, the critical chemical structure(s), and the usefulness of combining antimicrobial and anti-inflammatory properties, which during long-term treatment, could lead to increased microbial resistance. Also, because of the multiplicity of macrolide effects on different cell subsets, a unifying hypothesis for macrolide interactions with host cells is lacking. Novel analytical methods will certainly lead to new macrolide-based therapeutic strategies in cancer and inflammation.

Clinical implications of macrolide therapy in chronic sinopulmonary diseases.

Macrolides have broad antibacterial spectrum and proven efficacy in the management of respiratory tract infections. Over the past decade there has been progressive interest in these agents for their potential role as tissue modifying, anti-inflammatory agents. Increasingly, the effect of macrolides on numerous cell types has been documented. Preliminary data have suggested a beneficial clinical role of chronic macrolide therapy in selected patients with chronic rhinosinusitis, chronic obstructive pulmonary disease, cystic fibrosis, non-cystic fibrosis bronchiectasis and asthma. This review presents the biological rationale and the available clinical data of chronic macrolide therapy in chronic respiratory tract diseases. When available, the data addressing the presumed mechanisms underlying clinical benefits are presented.

Pladienolides, new substances from culture of Streptomyces platensis Mer-11107. I. Taxonomy, fermentation, isolation and screening.

Seven new macrolides having a 12-membered ring, which we termed pladienolides, were isolated from the fermentation broth of Streptomyces platensis Mer-11107. Six of the seven pladienolides inhibited hypoxia-induced reporter gene expression controlled by human VEGF promoter with IC50 values of 0.0018-2.89 microM. They also demonstrated growth-inhibitory activity against U251 human glioma cells in vitro. Pladienolides are highly potent inhibitors of both hypoxia signals and cancer cell proliferation, and thus may be useful as antitumor agents.

[Macrolides and drug interactions: review of the literature]. / Macrolides et interactions médicamenteuses: revue de la littérature.

Clarithromycin, azithromycin and dirithromycin have recently been introduced in France. We list the different drug-interactions with these three new drugs and with erythromycin, josamycin, roxithromycin, midecamycin and spiramycin.

Antifungal activity of the primycin complex and its main components A1, A2 and C1 on a Candida albicans clinical isolate, and their effects on the dynamic plasma membrane changes.

The in vitro antifungal activities of the macrolide lactone antibiotic complex primycin (PC) and its main components, A1 (50%), A2 (7.3%) and C1 (13%), against the opportunistic pathogenic fungus Candida albicans 33erg(+)were determined by microdilution testing. The MIC(100) (the minimal concentration required for 100% growth inhibition) values found, A2 (2 µg ml(-1)), PC (32 µg ml(-1)), A1 (32 µg ml(-1)) and C1 (64 µg ml(-1)), suggested that the biological activity of PC is highly dependent on the proportions of its constituents. In vivo measurements of the biophysical properties of plasma membranes were carried out by electron paramagnetic resonance (EPR) spectroscopic methods, using the spin probe 5-(4,4-dimethyloxazolidine-N-oxyl)stearic acid. Conventional EPR measurements demonstrated altered phase transition temperatures (Tm) of the plasma membrane of strain 33erg(+) as a consequence of treatment with PC or its constituents: for cells treated with 128 µg ml(-1) PC, A1, A2 or C1 for 15 min, Tm was 17, 21, 14.5 and 15 °C, respectively; that is significantly higher than the Tm of untreated cells, 12 °C. The molecular motions of the near-surface hydrophobic region of the plasma membrane, estimated by saturation transfer EPR spectroscopy, reflected changes in the membrane phases after the treatment. Two physiological membrane phases were detected in control samples: liquid-ordered and liquid-disordered, characterized by molecular movements ∼10(-6)-10(-8) s and ≥10(-9) s. The cells treated with the investigated compounds showed the strong presence of a non-physiological gel phase additional to the above phases, characterized by movements ≤10(-5) s.

Risks of population antimicrobial resistance associated with chronic macrolide use for inflammatory airway diseases.

Macrolide antibiotics have established efficacy in the management of cystic fibrosis and diffuse panbronchiolitis-uncommon lung diseases with substantial morbidity and the potential for rapid progression to death. Emerging evidence suggests benefits of maintenance macrolide treatment in more indolent respiratory diseases including chronic obstructive pulmonary disease and non-cystic fibrosis bronchiectasis. In view of the greater patient population affected by these disorders (and potential for macrolide use to spread to disorders such as chronic cough), widespread use of macrolides, particularly azithromycin, has the potential to substantially influence antimicrobial resistance rates of a range of respiratory microbes. In this Personal View, I explore theories around population (rather than patient) macrolide resistance, appraise evidence linking macrolide use with development of resistance, and highlight the risks posed by injudicious broadening of their use, particularly of azithromycin. These risks are weighed against the potential benefits of macrolides in less aggressive inflammatory airway disorders. A far-sighted approach to maintenance macrolide use in non-cystic fibrosis inflammatory airway diseases is needed, which minimises risks of adversely affecting community macrolide resistance: combining preferential use of erythromycin and restriction of macrolide use to those patients at greatest risk represents an appropriately cautious management approach.

A framework to analyze multiple time series data: a case study with Streptomyces coelicolor.

Transcriptional regulation in differentiating microorganisms is highly dynamic involving multiple and interwinding circuits consisted of many regulatory genes. Elucidation of these networks may provide the key to harness the full capacity of many organisms that produce natural products. A powerful tool evolved in the past decade is global transcriptional study of mutants in which one or more key regulatory genes of interest have been deleted. To study regulatory mutants of Streptomyces coelicolor, we developed a framework of systematic analysis of gene expression dynamics. Instead of pair-wise comparison of samples in different combinations, genomic DNA was used as a common reference for all samples in microarray assays, thus, enabling direct comparison of gene transcription dynamics across different isogenic mutants. As growth and various differentiation events may unfold at different rates in different mutants, the global transcription profiles of each mutant were first aligned computationally to those of the wild type, with respect to the corresponding growth and differentiation stages, prior to identification of kinetically differentially expressed genes. The genome scale transcriptome data from wild type and a DeltaabsA1 mutant of Streptomyces coelicolor were analyzed within this framework, and the regulatory elements affected by the gene knockout were identified. This methodology should find general applications in the analysis of other mutants in our repertoire and in other biological systems.

Iejimalides show anti-osteoclast activity via V-ATPase inhibition.

Iejimalides (IEJLs), 24-membered macrolides, are potent antitumor compounds, but their molecular targets remain to be revealed. In the course of screening, we identified IEJLs as potent osteoclast inhibitors. Since it is known that osteoclasts are sensitive to vacuolar H(+)-ATPase (V-ATPase) inhibitor, we investigated the effect of IEJLs on V-ATPases. IEJLs inhibited the V-ATPases of both mammalian and yeast cells in situ, and of yeast V-ATPases in vitro. A bafilomycin-resistant yeast mutant conferred IEJL resistance, suggesting that IEJLs bind a site similar to the bafilomycins/concanamycins-binding site. These results indicate that IEJLs are novel V-ATPase inhibitors, and that antitumor and antiosteporotic activities are exerted via V-ATPase inhibition.

Macrocyclic lactones: distribution in plasma lipoproteins of several animal species including humans.

We studied the in vitro distribution of macrocyclic lactones (MLs), lipophilic anthelmintic drugs, in the plasma of several animal species including humans. First, in vitro spiking of goat plasma was performed with ivermectin, moxidectin, abamectin, doramectin, or eprinomectin. In parallel, goats were treated with subcutaneous injection of ivermectin. Then, cow, sheep, rabbit, pig, and human plasma were spiked with moxidectin. Four fractions were separated using KBr density gradient ultracentrifugation: very-low-density lipoprotein (VLDL), low-density lipoprotein (LDL), high-density lipoprotein (HDL), and lipoprotein-deficient fraction. Cholesterol was analyzed by enzymatic assay and MLs by high-performance liquid chromatography. An average of 96% of MLs was associated with lipoproteins. The five MLs studied distributed similarly into goat plasma fractions with a preferential association with HDL (80-90%). Ivermectin partitioning in goat plasma was similar after in vitro spiking and in vivo treatment. In species displaying various lipoprotein profiles, moxidectin was also mainly associated with HDL. However, in human plasma, moxidectin was associated with a lesser extent to HDL (70%) and more to LDL (22%) when compared to other animal species. A relation between the plasma cholesterol content and pharmacokinetics of the drug is suggested. Our finding will allow further exploration of intestinal lymphatic absorption and milk elimination of these compounds-mechanisms in which lipoproteins are involved. In addition, possible improvements of new drug delivery systems are suggested.