Distinct mechanisms contribute to immunity in the lantibiotic NAI‐107 producer strain Microbispora ATCC PTA‐5024

The investigation of self‐resistance in antibiotic producers is important to understand the emergence of antibiotic resistance in pathogens and to improve antibiotic production. Lantibiotics are ribosomally synthesized antibiotics that mostly target peptidoglycan biosynthesis. The actinomycete Microbispora ATCC PTA‐5024 produces the lantibiotic NAI‐107, which interferes with peptidoglycan biosynthesis by binding bactoprenol‐pyrophosphate‐coupled peptidoglycan precursors. In order to understand how Microbispora counteracts the action of its own antibiotic, its peptidoglycan composition was analysed in detail. Microbispora peptidoglycan consists of muropeptides with D‐Ala and Gly in similar proportion at the fourth position of the peptide stems and alternative 3‐3 cross‐links besides the classical 4‐3 cross‐links. In addition, the NAI‐107 biosynthetic gene cluster (mlb) was analysed for the expression of immunity proteins. We show that distinct immunity determinants are encoded in the mlb cluster: the ABC transporter MlbYZ acting cooperatively with the transmembrane protein MlbJ and the lipoprotein MlbQ. NMR structural analysis of MlbQ revealed a hydrophobic surface patch, which is proposed to bind the cognate lantibiotic. This study demonstrates that immunity in Microbispora is not only based on one determinant but on the action of the distinct immunity proteins MlbQ, MlbYZ and MlbJ.     

Biosynthesis,biotechnological production,and application of teicoplanin: current state and perspectives

The glycopeptide teicoplanin isolated from the fermentation broth of Actinoplanes teichomyceticus is used to treat serious Gram-positive bacterial infections that are resistant to other antibiotics, e.g. β-lactams. The long time frame and progressively broader clinical use of teicoplanin has eventually led to the emergence and spreading of resistance in enterococci and staphylococci towards the antibiotics. Given the structural complexity of the natural product, only fermentative routes are available for bulk production of teicoplanin even though the total synthesis of the antibiotic has been accomplished. Because the low productivity (0.1–3.1 g/L) is a limitation to the commercial production of teicoplanin, substantial effort has been devoted to the strain improvement and process development for enhancing the productivity. This review summarizes the current state of the action mechanism, antibacterial activity, resistance mechanism, biotechnological production, and application of teicoplanin. Hyung-Moo Jung and Marimuthu Jeya equally contributed to this work.     

Production,by filamentous,nitrogen-fixing cyanobacteria,of a bacteriocin and of other antibiotics that kill related strains

Colonies of sixty-five filamentous cyanobacteria were screened for the production of temperate phages and/or antibiotics on solid medium. None of them was observed to release phages. However, seven N₂-fixing strains were found to produce antibiotics very active against other cyanobacteria. The antibiotic produced by Nostoc sp. 78-11 A-E represents a bacteriocin of low molecular weight. Nostoc sp. ATCC 29132 appears to secrete, together with an antibiotic, a protein that inhibits its action.     

Quantitative systematic review of randomised controlled trials comparing antibiotic with placebo for acute cough in adults

Objectives: To assess whether antibiotic treatment for acute cough is effective and to measure the side effects of such treatment. Design: Quantitative systematic review of randomised placebo controlled trials. Data sources: Nine trials (8 published, 1 unpublished) retrieved from a systematic search (electronic databases, contact with authors, contact with drug manufacturers, reference lists); no restriction on language. Main outcome measures: Proportion of subjects with productive cough at follow up (7-11 days after consultation with general practitioner); proportion of subjects who had not improved clinically at follow up; proportion of subjects who reported side effects from taking antibiotic or placebo. Results: Eight trials contributed to the meta-analysis. Resolution of cough was not affected by antibiotic treatment (relative risk 0.85 (95% confidence interval 0.73 to 1.00)), neither was clinical improvement at re-examination (relative risk 0.62 (0.36 to 1.09)). The side effects of antibiotic were more common in the antibiotic group when compared to placebo (relative risk 1.51 (0.86 to 2.64)). Conclusions: Treatment with antibiotic does not affect the resolution of cough or alter the course of illness. The benefits of antibiotic treatment are marginal for most patients with acute cough and may be outweighed by the side effects of treatment.

Key messages

• Acute cough, with or without sputum, is a common reason for consulting a general practitioner
• Although antibiotic treatment is common for this condition, its likely benefits and side effects have not been measured
• This systematic review reports the outcome of nine randomised controlled trials that compared antibiotic with placebo in patients with acute cough
• Resolution of cough and clinical improvement at follow up was no different in the two groups
• The benefits of antibiotic treatment seem to be marginal for most patients with acute cough and may be outweighed by the side effects of treatment

     

Functional characterization of a three-component regulatory system involved in quorum sensing-based regulation of peptide antibiotic production in Carnobacterium maltaromaticum

Background  

Quorum sensing is a form of cell-to-cell communication that allows bacteria to control a wide range of physiological processes in a population density-dependent manner. Production of peptide antibiotics is one of the processes regulated by quorum sensing in several species of Gram-positive bacteria, including strains of Carnobacterium maltaromaticum. This bacterium and its peptide antibiotics are of interest due to their potential applications in food preservation. The molecular bases of the quorum sensing phenomenon controlling peptide antibiotic production in C. maltaromaticum remain poorly understood. The present study was aimed at gaining a deeper insight into the molecular mechanism involved in quorum sensing-mediated regulation of peptide antibiotic (bacteriocin) production by C. maltaromaticum. We report the functional analyses of the CS (autoinducer)-CbnK (histidine protein kinase)-CbnR (response regulator) three-component regulatory system and the three regulated promoters involved in peptide antibiotic production in C. maltaromaticum LV17B.     

Structural changes induced by a lytic bacteriophage make ciprofloxacin effective against older biofilm of Klebsiella pneumoniae

Bacteria have evolved multiple mechanisms, such as biofilm formation, to thwart antibiotic action. Yet antibiotics remain the drug of choice against clinical infections. It has been documented that young biofilm of Klebsiella pneumoniae could be eradicated significantly by ciprofloxacin treatment alone. Since age of biofilm is a decisive factor in determining the outcome of antibiotic treatment, in the present study biofilm of K. pneumoniae, grown for extended periods was treated with ciprofloxacin and/or depolymerase producing lytic bacteriophage (KPO1K2). The reduction in bacterial numbers of older biofilm was greater after application of the two agents in combination as ciprofloxacin alone could not reduce bacterial biomass significantly in older biofilms (P > 0.05). Confocal microscopy suggested the induction of structural changes in the biofilm matrix and a decrease in micro-colony size after KPO1K2 treatment. The role of phage associated depolymerase was emphasized by the insignificant eradication of biofilm by a non-depolymerase producing bacteriophage that, however, eradicated the biofilm when applied concomitantly with purified depolymerase. These findings demonstrate that a lytic bacteriophage alone can eradicate older biofilms significantly and its action is primarily depolymerase mediated. However, application of phage and antibiotic in combination resulted in slightly increased biofilm eradication confirming the speculation that antibiotic efficacy can be augmented by bacteriophage.     

Design of mineral medium for growth of <Emphasis Type="Italic">Actinomadura</Emphasis> sp. ATCC 39727, producer of the glycopeptide A40926: effects of calcium ions and nitrogen sources

Actinomadura sp. ATCC 39727 produces the glycopeptide antibiotic A40926, structurally similar to teicoplanin, with significant activity against Neisseria gonorrhoeae and precursor of the semi-synthetic antibiotic dalbavancin. In this study the production of A40926 by Actinomadura under a variety of growth conditions was investigated. The use of chemically defined mineral media allowed us to analyze the influence of carbon and nitrogen sources, phosphate, ammonium and calcium on the growth and the antibiotic productivity of Actinomadura. We confirm recent data [Gunnarsson et al. (2003) J Ind Microbiol Biotechnol 30:150–156] that low initial concentrations of phosphate and ammonium are beneficial for growth and A40926 production, and we provide new evidence that the production of A40926 is depressed by calcium, but promoted when l-glutamine or l-asparagine are used as nitrogen sources instead of ammonium salts.     

Streptomyces species producing the streptovaricin complex

Morphological, cultural and physiological-biochemical properties ofStreptomyces sp. strain 1000 and its antibiotic production were investigated. Antibiotics 1011 (identical with the streptovaricin complex) and 1012 (with antibacterial action) were isolated from the cultural broth of this strain. The overproducing natural variant 1011 was isolated from the population of a strain producing antibiotic 1011 at a concentration of 1000 mg/L (activity of the parent strain represents 41 mg/L only). Comparative taxonomical characteristic ofStreptomyces sp. strain 1000 with strains fromS. spectabilis showed that the strain 1000 differed in some properties and antibiotic production being considered as a new variant ofS. spectabilis. The strain shows an expressed antibiotic activity against G+ as well as G− bacterial and yeasts.     

Intracellular ATP Levels Affect Secondary Metabolite Production in Streptomyces spp.

The addition of extracellular ATP (exATP) to four Streptomyces strains had similar effects: low exATP levels stimulated antibiotic production and high levels reduced it. Compared with antibiotic production, the concentrations of intracellular ATP (inATP) in the tested strains were opposite, which suggests a role of inATP in regulating secondary metabolite production. Under inactivation of the polyphosphate kinase gene (ppk) in Streptomyces lividans, we observed the same results: when the inATP level in the mutant strain was lower than in the parent strain, more antibiotic was produced. Combining all the results, a strong inverse relationship between [inATP] and the secondary metabolite production is suggested by this study.     

EFFECTS OF ELECTRICALLY GENERATED SILVER IONS ON HUMAN CELLS AND WOUND HEALING

A method of producing local antibiotic effects by means of an iontophoretic technique using free silver ions has been evaluated in vitro and in vivo for more than two decades. The antibiotic properties of the technique have proved useful in both animal and human studies. In the course of determining the optimal clinical methodology for infected open wounds, a significant growth stimulation property resembling local tissue regeneration was noted. This has been traced to either the apparent production of dedifferentiation of normal mature cells or the stimulation of preexisting stem cells in the wound, resulting in the production of large numbers of progenitor cells. This process has now been studied in detail, and the results are presented herewith.     

From nutraceutical to clinical trial: frontiers in Ganoderma development

Ganoderma spp. are medical mushrooms with various pharmacological compounds which are regarded as a nutraceutical for improving health and treating diseases. This review summarizes current progress in the studies of Gamoderma ranging from bioactive metabolites, bioactivities, production techniques to clinical trials. Traditionally, polysaccharides and ganoderic acids have been reported as the major bioactive metabolites of Ganoderma possessing anti-tumor and immunomodulation functions. Moreover, recent studies indicate that Gandoerma also exerts other bioactivities such as skin lighting, gut microbiota regulation, and anti-virus effects. However, since these medical fungi are rare in natural environment, and that the cost of cultivation of fruiting bodies is high, industrial submerged fermentation of Ganoderma mycelia promotes the development of Ganoderma by dint of an increase of biomass and bioactive metabolites used for further application. In addition, various strategies for production of different metabolites are well developed, such as gene regulation, bi-stage pH, and oxygen control. To date, Ganoderma not only has become one of the most popular nutraceuticals worldwide but also has been applied to clinical trials for advanced diseases such as breast and non-small-cell lung cancer.

     

Cloning,reassembling and integration of the entire nikkomycin biosynthetic gene cluster into <Emphasis Type="Italic">Streptomyces ansochromogenes</Emphasis> lead to an improved nikkomycin production

Background  

Nikkomycins are a group of peptidyl nucleoside antibiotics produced by Streptomyces ansochromogenes. They are competitive inhibitors of chitin synthase and show potent fungicidal, insecticidal, and acaricidal activities. Nikkomycin X and Z are the main components produced by S. ansochromogenes. Generation of a high-producing strain is crucial to scale up nikkomycins production for further clinical trials.     

Optimization of fermentation condition for antibiotic production by Xenorhabdus nematophila with response surface methodology

Aims: To evaluate the influence of environmental parameters on the production of antibiotics (xenocoumacins and nematophin) by Xenorhabdus nematophila and enhance the antibiotic activity. Methods and Results: Response surface methodology (RSM) was employed to study the effects of five parameters (the initial pH, medium volume in flask, rotary speed, temperature and inoculation volume) on the production of antibiotics in flask cultures by X. nematophila YL001. A 2^5?1‐factorial central composite design was chosen to explain the combined effects of the five parameters and to design a minimum number of experiments. The experimental results and software‐predicted values of production of antibiotics were comparable. The statistical analysis of the results showed that, in the range studied, medium volume in flask, rotary speed, temperature and inoculation volume had a significant effect (P < 0·05) on the production of antibiotics at their individual level, medium volume in flask and rotary speed showed a significant influence at interactive level and were most significant at individual level. The maximum antibiotic activity was achieved at the initial pH 7·64, medium volume in 250 ml flask 25 ml, rotary speed of 220 rev min^?1, temperature 27·8°C and inoculation volume of 15·0%. Maximum antibiotic activity of 331·7 U ml^?1 was achieved under the optimized condition. Conclusions: As far as known, there are no reports of production of antibiotic from X. nematophila by engineering the condition of fermentation using RSM. The results strongly support the use of RSM for fermentation condition optimization. The optimization of the environmental parameters resulted not only in a 43·4% higher antibiotic activity than unoptimized conditions but also in a reduced amount of the experiments. The chosen method of optimization of fermentation condition was efficient, relatively simple and time and material saving. Significance and Impact of the Study: This study should contribute towards improving the antibiotics activity of X. nematophila. Integrated into a broader study of the impact of environmental factors on the production of antibiotic, this work should help to build more rational control strategy, possibly involving scale‐up of production of antibiotics by X. nematophila.     

Studies on Fungal Tannase

The possibility that selective inhibition of phage by antibiotic may be achieved by using bacterial mutant resistant to the antibiotic was investigated in the system of HM-phages of Clostridium saccharoperbutylacetonicum, a butanol-producing bacterium.

Consequently, it was found that Oxytetracycline, using the antibiotic-resistant mutant as host, inhibited selectively the growth of HM-phages. The bacterial mutant termed type A (one-step mutant resistant to 30 μg/ml of Oxytetracycline) did not permit the growth of HM-phages (HM 2 and HM 3) in the presence of the antibiotic (ca. 10 μg/ml), though it permitted the growth of the phages in the absence of the antibiotic.

An analysis of the mode of action of Oxytetracycline in HM 2-phage system revealed the following, (i) The antibiotic had a slight phagicidal action, (ii) It did not prevent the phage adsorption, (iii) It inhibited the protein synthesis in phage-infected cells, (iv) It inhibited the lysis of infected cells. Active phages were, however, not detected when the lysis-inhibited cells were artificially lysed.

Another type of bacterial mutant was also encountered. In this mutant termed type B the development of resistance to Oxytetracycline (30 μg/ml) was associated with a simultaneous loss of sensitivity to particular phages (HM 2 group).     

Expression of a polycistronic messenger RNA involved in antibiotic production in an rnc mutant of Streptomyces coelicolor

RNase III is a double strand specific endoribonuclease that is involved in the regulation of gene expression in bacteria. In Streptomyces coelicolor, an RNase III (rnc) null mutant manifests decreased ability to synthesize antibiotics, suggesting that RNase III globally regulates antibiotic production in that species. As RNase III is involved in the processing of ribosomal RNAs in S. coelicolor and other bacteria, an alternative explanation for the effects of the rnc mutation on antibiotic production would involve the formation of defective ribosomes in the absence of RNase III. Those ribosomes might be unable to translate the long polycistronic messenger RNAs known to be produced by operons containing genes for antibiotic production. To examine this possibility, we have constructed a reporter plasmid whose insert encodes an operon derived from the actinorhodin cluster of S. coelicolor. We show that an rnc null mutant of S. coelicolor is capable of translating the polycistronic message transcribed from the operon. We show further that RNA species with the mobilities expected for mature 16S and 23S ribosomal RNAs are produced in the rnc mutant even though the mutant contains higher levels of the 30S rRNA precursor than the wild-type strain.     

Production of a potentially novel anti-microbial substance by Bacillus polymyxa

A bacterial strain, SCE2, identified as Bacillus polymyxa, produced an anti-microbial substance active against yeasts, fungi and different genera of Gram-positive and-negative bacteria, in liquid medium and in plate assays. This substance appeared to be an antibiotic different from the polymyxin group, mainly because of its action against the majority of Gram-positive bacteria tested and its lack of activity against Pseudomonas aeruginosa, a species usually killed by polymyxins. Preliminary characterization showed resistance to heat (65°C, 2 h), to proteases, trypsin, lysozyme, deoxyribonuclease I, ribonuclease A, phospholipase C, ethanol, acetone, chloroform, ether and to strong alkali treatment (2 M NaOH). The molecular weight was less than 3500. The B. polymyxa strain harboured a plasmid that did not correlate with antibiotic production; after curing experiments, a derivative strain, SCE2(46), was isolated that lacked the plasmid pES1, but showed the same inhibitory spectrum as the wild-type strain.     

Viomycin favours the formation of 70S ribosome couples

Summary The peptide antibiotic viomycin at a concentration of 10 M inhibits E. coli ribosomes to the extent of about 70% as measured in the poly(U) system, and to about 85% in a natural mRNA (R17) system. Ribosomes from M. smegmatis show no activity at all at this concentration of the antibiotic. Experiments on the Mg²⁺ dependent dissociation and association of the ribosomal subunits revealed that viomycin stabilizes the 70S couples and promotes association of ribosomal subunits. This response is related to the drug action as indicated by the observation that viomycin resistant strains are not affected by viomycin with respect to dissociation and 70S couple information. A model for the inhibitory action of the drug is proposed.     

Antibiotic resistance in bacteria associated with coarse atmospheric particulate matter in an urban area

Aims: To assess antibiotic resistance in airborne bacteria associated with coarse particulate matter (PM10) in an urban area, with specific considerations about the Staphylococcus genus. Methods and Results: Disc diffusion test was performed on 243 microbial strains, isolated from PM10 in winter and summer and belonging to families Pseudomonadaceae and Enterobacteriaceae and genera Acinetobacter, Enterococcus and Staphylococcus. Staphylococci resistances were the most heterogeneous, being distributed among almost all tested antibiotics. Staphylococcus isolates resistant to some selected antibiotics were further investigated for the presence of the corresponding genetic determinants. Only tetK, which mediates the tetracycline resistance through the action of an efflux protein, was found in almost all resistant isolates. Conclusions: The lack of specific genetic determinants makes their transmission among staphylococci less likely. This may reduce the theoretical risk associated with the inhalation of airborne micro‐organisms. Significance and Impact of Study: Although the spreading of antibiotic resistant micro‐organisms is of particular concern in clinical settings, the origin of antibiotic resistance genes can be traced in natural environments. As behaviour, viability and transport of bacteria in the atmospheric compartment suffer from a lack of information, the evaluation of the actual risk posed by airborne micro‐organisms to human health is still challenging.