Activity of the investigational fluoroquinolone finafloxacin and seven other antimicrobial agents against 114 obligately anaerobic bacteria.

The activity of finafloxacin against 73 strains of the Bacteroides fragilis group, 10 other Gram-negative anaerobic rods and 31 Clostridium difficile strains was determined by the broth microdilution technique. The activity was compared with that of moxifloxacin, levofloxacin, ciprofloxacin, clindamycin, imipenem, piperacillin/tazobactam and metronidazole. MIC(50/90) values (minimum inhibitory concentration, in μg/mL, at which 50% and 90% of the isolates tested are inhibited, respectively) for finafloxacin for the different species were determined: B.

Uniformity of glycyl bridge lengths in the mature cell walls of fem mutants of methicillin-resistant Staphylococcus aureus.

Peptidoglycan (PG) composition in intact cells of methicillin-resistant Staphylococcus aureus (MRSA) and its isogenic Fem mutants has been characterized by measuring the glycine content of PG bridge structures by solid-state nuclear magnetic resonance (NMR). The glycine content estimated from integrated intensities (rather than peak heights) in the cell walls of whole cells was increased by approximately 30% for the FemA mutant and was reduced by 25% for the FemB mutant relative to expected values for homogeneous structures. In contrast, the expected compositions were observed in isolated cell walls of the same mutants.

In vitro spectrum of activity of finafloxacin, a novel, pH-activated fluoroquinolone, under standard and acidic conditions.

Finafloxacin is a novel fluoroquinolone that exhibits enhanced antibacterial activity under acidic conditions. The aim of this study was to define the in vitro pH-activity relationship. Finafloxacin exhibited optimal antibacterial activity between pH 5.

Human pharmacokinetics and safety profile of finafloxacin, a new fluoroquinolone antibiotic, in healthy volunteers.

Finafloxacin is a new fluoroquinolone antibiotic with the unique property of increasing antibacterial activity at pH values lower than neutral. Whereas its antibacterial activity at neutral pH matches that of other quinolones in clinical use, it is expected to surpass this activity in tissues and body fluids acidified by the infection or inflammation processes. Pharmacokinetic parameters of oral single and multiple doses of up to 800 mg of finafloxacin and safety/tolerability observations were assessed in a phase I study including 95 healthy volunteers.

Antibacterial activity of finafloxacin under different pH conditions against isogenic strains of Escherichia coli expressing combinations of defined mechanisms of fluoroquinolone resistance.

Objectives: Finafloxacin is an investigational fluoroquinolone exhibiting broad-spectrum activity that is enhanced under slightly acidic conditions (pH 5.0-6.5).

Characterization of peptidoglycan in fem-deletion mutants of methicillin-resistant Staphylococcus aureus by solid-state NMR.

Compositional analysis of the peptidoglycan (PG) of a wild-type methicillin-resistant Staphylococcus aureus and its fem-deletion mutants has been performed on whole cells and cell walls using stable-isotope labeling and rotational-echo double-resonance NMR. The labels included [1-(13)C,(15)N]glycine and l-[epsilon-(15)N]lysine (for a direct measure of the number of glycyl residues in the bridging segment), [1-(13)C]glycine and l-[epsilon-(15)N]lysine (concentration of bridge links), and d-[1-(13)C]alanine and [(15)N]glycine (concentrations of cross-links and wall teichoic acids). The bridging segment length changed from 5.

Daptomycin versus Friulimicin B: in-depth profiling of Bacillus subtilis cell envelope stress responses.

The related lipo(depsi)peptide antibiotics daptomycin and friulimicin B show great potential in the treatment of multiply resistant gram-positive pathogens. Applying genome-wide in-depth expression profiling, we compared the respective stress responses of Bacillus subtilis. Both antibiotics target envelope integrity, based on the strong induction of extracytoplasmic function sigma factor-dependent gene expression.

The lipopeptide antibiotic Friulimicin B inhibits cell wall biosynthesis through complex formation with bactoprenol phosphate.

Friulimicin B is a naturally occurring cyclic lipopeptide, produced by the actinomycete Actinoplanes friuliensis, with excellent activity against gram-positive pathogens, including multidrug-resistant strains. It consists of a macrocyclic decapeptide core and a lipid tail, interlinked by an exocyclic amino acid. Friulimicin is water soluble and amphiphilic, with an overall negative charge.

New antibiotics for antibiotic-resistant bacteria.

The need for new antibiotics to effectively treat antibiotic-resistant infections remains unfulfilled. Despite the well-publicised concern over this issue, only two novel antibiotic classes have been introduced in the past 20 years alongside several new agents of existing classes. Accordingly, the current antibiotic armoury remains inadequate to meet the challenges posed by resistance today.

In vitro and in vivo validation of ligA and tarI as essential targets in Staphylococcus aureus.

A conditional expression system has been developed using the isopropyl-beta-d-thiogalactopyranoside (IPTG)-inducible Pspac promoter to validate essential genes of Staphylococcus aureus in vivo. The system has been applied to prove the essentiality of ligA and to evaluate the function of tarI, which was found to be essential in vitro but not in vivo.

Characterization of a daptomycin-nonsusceptible vancomycin-intermediate Staphylococcus aureus strain in a patient with endocarditis.

We analyzed the emergence of daptomycin nonsusceptibility in a patient with persistent vancomycin-intermediate Staphylococcus aureus (VISA) bacteremia. The daptomycin-nonsusceptible VISA's cell wall demonstrated a reduction in muramic acid O-acetylation, a phenotypic parameter not previously reported for VISA; some isolates also contained a single point mutation in the mprF gene.

Dysregulation of bacterial proteolytic machinery by a new class of antibiotics.

Here we show that a new class of antibiotics-acyldepsipeptides-has antibacterial activity against Gram-positive bacteria in vitro and in several rodent models of bacterial infection. The acyldepsipeptides are active against isolates that are resistant to antibiotics in clinical application, implying a new target, which we identify as ClpP, the core unit of a major bacterial protease complex. ClpP is usually tightly regulated and strictly requires a member of the family of Clp-ATPases and often further accessory proteins for proteolytic activation.

Novel anti-staphylococcal targets and compounds.

Many antimicrobial drugs have become less effective at combating infectious diseases, and experts in the field are concerned about the possibility of a 'post-antibiotic era' for some clinically important pathogens, particularly staphylococci. In our hospitals, nosocomial infections due to vancomycin-resistant enterococci have emerged, and there are concerns that the same resistance pattern may evolve in methicillin-resistant Staphylococcus aureus (MRSA). Examples from three main areas addressed to prevent this scenario are discussed: (i) screening of isolated biochemical targets and intact bacteria using high-throughput screening technologies, (ii) modifying existing compound classes like quinolones and glycopeptides to create more powerful compounds overcoming pathogen resistance and (iii) introduction of completely new classes of antibiotics.

Staphylococcus aureus NfrA (SA0367) is a flavin mononucleotide-dependent NADPH oxidase involved in oxidative stress response.

The NfrA protein, a putative essential oxidoreductase in the soil bacterium Bacillus subtilis, is induced under heat shock and oxidative stress conditions. In order to characterize the function of an homologous NfrA protein in Staphylococcus aureus, an nfrA deletion strain was constructed, the protein was purified, the enzymatic activity was determined, and the transcriptional regulation was investigated. The experiments revealed that NfrA is not essential in S.

The impact of transcriptome and proteome analyses on antibiotic drug discovery.

Recent scientific publications demonstrate the increasing interest in measurement of genome-wide gene expression on transcript and protein level in response to treatment with antibacterial agents. Nevertheless, the number of large bacterial transcriptome and proteome datasets available so far is limited, although a high number and diversity of antibiotic-triggered expression profiles aid to optimally exploit these technologies. The first published examples substantiate the need to establish these so-called reference compendia of bacterial expression profiles, to discover the molecular mechanism-of-action of uncharacterized bioactive substances.

Antibacterial research and development in the 21(st) Century--an industry perspective of the challenges.

The continued evolution of resistance to antibiotics has led to wide ranging consultation at National and International levels as to how to address this issue. In addition to attempting to limit the spread of resistance there is growing consensus that a cornerstone requirement is the development of new antibiotics to help redress the balance of resistance versus available antibiotics. The availability of new technologies such as genomics has opened up new approaches for antibacterial research.

Bacterial proteomics and its role in antibacterial drug discovery.

Gene-expression profiling technologies in general, and proteomic technologies in particular have proven extremely useful to study the physiological response of bacterial cells to various environmental stress conditions. Complex protein toolkits coordinated by sophisticated regulatory networks have evolved to accommodate bacterial survival under ever-present stress conditions such as varying temperatures, nutrient availability, or antibiotics produced by other microorganisms that compete for habitat. In the last decades, application of man-made antibacterial agents resulted in additional bacterial exposure to antibiotic stress.

Cell wall composition and decreased autolytic activity and lysostaphin susceptibility of glycopeptide-intermediate Staphylococcus aureus.

The cell wall composition and autolytic properties of passage-selected glycopeptide-intermediate Staphylococcus aureus (GISA) isolates and their parent strains were studied in order to investigate the mechanism of decreased vancomycin susceptibility. GISA had relatively modest changes in peptidoglycan composition involving peptidoglycan interpeptide bridges and somewhat decreased cross-linking compared to that of parent strains. The cell wall phosphorus content of GISA strains was lower than that of susceptible parent strains, indicating somewhat lower wall teichoic acid levels in the GISA strains.

Specific and potent inhibition of NAD+-dependent DNA ligase by pyridochromanones.

Pyridochromanones were identified by high throughput screening as potent inhibitors of NAD+-dependent DNA ligase from Escherichia coli. Further characterization revealed that eubacterial DNA ligases from Gram-negative and Gram-positive sources were inhibited at nanomolar concentrations. In contrast, purified human DNA ligase I was not affected (IC50 > 75 microm), demonstrating remarkable specificity for the prokaryotic target.

Proteomic approach to understanding antibiotic action.

We have used proteomic technology to elucidate the complex cellular responses of Bacillus subtilis to antimicrobial compounds belonging to classical and emerging antibiotic classes. We established on two-dimensional gels a comprehensive database of cytoplasmic proteins with pIs covering a range of 4 to 7 that were synthesized during treatment with antibiotics or agents known to cause generalized cell damage. Although each antibiotic showed an individual protein expression profile, overlaps in the expression of marker proteins reflected similarities in molecular drug mechanisms, suggesting that novel compounds with unknown mechanisms of action may be classified.

Molecular characterization of an atl null mutant of Staphylococcus aureus.

atl is a gene encoding a bifunctional peptidoglycan hydrolase of Staphylococcus aureus. The gene product of atl is a 138 kDa protein that has an amidase domain and a glucosaminidase domain, and undergoes processing to generate two major peptidoglycan hydrolases, a 51 kDa glucosaminidase and a 62 kDa amidase in culture supernatant. An atl null mutant was isolated by allelic replacement and characterized.

Emergence, mechanism, and clinical implications of reduced glycopeptide susceptibility in Staphylococcus aureus.

In order to understand the mechanism(s) of the resistance/reduced susceptibility of Staphylococcus aureus to glycopeptide antibiotics, the current data on the modes of action of glycopeptides were reviewed. In addition, the different test systems for detecting vancomycin resistance and the clinical relevance of resistant Staphylococcus aureus were analyzed. Finally, strategies to prevent the nosocomial spread of these bacteria are presented, as are new therapeutic options.

Increased glycan chain length distribution and decreased susceptibility to moenomycin in a vancomycin-resistant Staphylococcus aureus mutant.

A vancomycin-resistant Staphylococcus aureus mutant, COL-VR1 (MIC, 16 microg/ml), was isolated from methicillin-resistant S. aureus COL by exposure to vancomycin. COL-VR1 also showed decreased susceptibility to teicoplanin (8-fold), methicillin (2-fold), macarbomycin (8-fold), and moenomycin (16-fold).