Codeine dysregulates ribosome biogenesis in Escherichia coli with DNA double-strand breaks to chart path to new classes of antibiotics.

4-Hydroxy-2,5-dihydrothiazole derivatives as a new class of small-molecule antibiotics for MRSA: AI-integrated design, chemical synthesis and biological evaluation.

ABSTRACTNew treatments are needed for extensively drug-resistant (XDR) Gram-negative bacilli (GNB), such as Acinetobacter baumannii. Toll-like receptor 4 (TLR4) was previously reported to enhance bacterial clearance of GNB, including A. baumannii. However, here we have shown that 100% of wild-type mice versus 0% of TLR4-deficient mice died of septic shock due to A. baumannii infection, despite having similar tissue bacterial burdens. The strain lipopolysaccharide (LPS) content and TLR4 activation by extracted LPS did not correlate with in vivo virulence, nor did colistin resistance due to LPS phosphoethanolamine modification. However, more-virulent strains shed more LPS during growth than less-virulent strains, resulting in enhanced TLR4 activation. Due to the role of LPS in A. baumannii virulence, an LpxC inhibitor (which affects lipid A biosynthesis) antibiotic was tested. The LpxC inhibitor did not inhibit growth of the bacterium (MIC > 512 µg/ml) but suppressed A. baumannii LPS-mediated activation of TLR4. Treatment of infected mice with the LpxC inhibitor enhanced clearance of the bacteria by enhancing opsonophagocytic killing, reduced serum LPS concentrations and inflammation, and completely protected the mice from lethal infection. These results identify a previously unappreciated potential for the new class of LpxC inhibitor antibiotics to treat XDR A. baumannii infections. Furthermore, they have far-reaching implications for pathogenesis and treatment of infections caused by GNB and for the discovery of novel antibiotics not detected by standard in vitro screens.

It has been nearly 50 years since the golden age of antibiotic discovery (1945–1975) ended; yet, we still struggle to identify novel drug targets and to deliver new chemical classes of antibiotics to replace those rendered obsolete by drug resistance. Despite herculean efforts utilizing a wide range of antibiotic discovery platform strategies, including genomics, bioinformatics, systems biology and postgenomic approaches, success has been at best incremental. Obviously, finding new classes of antibiotics is really hard, so repeating the old strategies, while expecting different outcomes, seems to boarder on insanity. The key questions dealt with in this review include: (1) If mutation based drug resistance is the major challenge to any new antibiotic, is it possible to find drug targets and new chemical entities that can escape this outcome; (2) Is the number of novel chemical classes of antibacterials limited by the number of broad spectrum drug targets; and (3) If true, then should we focus efforts on subgroups of pathogens like Gram negative or positive bacteria only, anaerobic bacteria or other group where the range of common essential genes is likely greater?. This review also provides some examples of existing drug targets that appear to escape the specter of mutation based drug resistance, and provides examples of some intermediate spectrum strategies as well as modern molecular and genomic approaches likely to improve the odds of delivering 21st century medicines to combat multidrug resistant pathogens.

Structure-based design of guanosine analogue inhibitors targeting GTP cyclohydrolase IB towards a new class of antibiotics

Ambruticin is a cyclopropyl-pyran acid, representing a new class of antibiotics. It has a relatively broad antifungal spectrum in vitro and is highly active against dimorphic as well as filamentous organisms. Of 24 strains of dermatophytic fungi tested, the majority were susceptible to ambruticin at 0.049 mug/ml or less. The minimal inhibitory concentration for the systemic fungi Histoplasma capsulatum and Blastomyces dermatitidis was 0.049 to 0.39 mug/ml. Ambruticin is fungicidal for metabolizing cells of Microsporum fulvum and does not cause cell leakage of 260-nm absorbing material. The antibiotic is effective orally as well as topically in guinea pigs experimentally infected with Trichophyton mentagrophytes. In mice, a single oral dose of 75 mg/kg produced peak serum levels of 45 mug/ml in 1 h with a serum half-life of 3.1 h. Excretion of the antibiotic is principally by the biliary route.

Antimicrobial resistance results in increased morbidity and mortality, and increased health-care costs. Therefore the need to develop new classes of antibiotics is indispensable. Antimicrobial peptides are a relatively new class of potential antibiotics which are fast acting, possess broad-spectrum activity and are able to escape many of the currently known mechanisms of drug resistance. They have been shown to be active against Gram-negative and Gram-positive bacteria, fungi, enveloped viruses and even cancer cells. However, toxicity to healthy host cells remains a concern and has affected the clinical development of therapeutics based on antimicrobial peptides. The purpose of this review is to discuss recent advances in research focused on antimicrobial peptides from frogs and the challenges in conducting research in this area in southern Africa. An extensive literature review of relevant articles published between 1980 and the present was conducted using PubMed, ScienceDirect, Sabinet, Elsevier and GoogleScholar. There has been little research done on anurans from southern Africa which are endemic to the region, and there is therefore a need to focus on this group for the purposes of bioprospecting for potentially new antimicrobial peptide compounds.

Multidrug-resistant bacteria are spreading at alarming rates, and despite extensive efforts no new class of antibiotic with activity against Gram-negative bacteria has been approved in over fifty years. Natural products and their derivatives have a key role in combating Gram-negative pathogens. Here we report chemical optimization of the arylomycins-a class of natural products with weak activity and limited spectrum-to obtain G0775, a molecule with potent, broad-spectrum activity against Gram-negative bacteria. G0775 inhibits the essential bacterial type I signal peptidase, a new antibiotic target, through an unprecedented molecular mechanism. It circumvents existing antibiotic resistance mechanisms and retains activity against contemporary multidrug-resistant Gram-negative clinical isolates in vitro and in several in vivo infection models. These findings demonstrate that optimized arylomycin analogues such as G0775 could translate into new therapies to address the growing threat of multidrug-resistant Gram-negative infections.

In their article “Exploitation of mammalian host cell functions by bacterial pathogens” (2 May, p. 718), B. Brett Finlay and Pascale Cossart state (p. 718), “No new class of antibiotic has been discovered in the past three decades, and derivatives of current antibiotics soon encounter resistance.” During the past 15 years, a group of small cationic antibiotic peptides has been shown to be produced by several animal species, including the cecropins of insects, the magainins of amphibian skin, and the defensins of mammalian neutrophils ([1][1]). The simple chemical structures of many of these antibiotics enabled the use of solid-phase peptide synthesis technology to rapidly create thousands of structural analogs and derivatives, some of which are currently in clinical trails (2). 1. [↵][2]1. R. E. W. Hancock , Lancet 349, 418 (1997). [OpenUrl][3][CrossRef][4][PubMed][5][Web of Science][6] 2. 1. H. G. Bowman 2. et al. , FEBS Lett. 259, 103 (1989). [OpenUrl][7][CrossRef][8][PubMed][9][Web of Science][10] # {#article-title-2} We agree with Wade's statement regarding the antibacterial activity of small cationic peptides and their promise as therapeutic agents. In our article, our statement referred to antibiotics that are currently in clinical use—no new chemical class of antibiotic has been introduced into clinical practice since 1981. At present, only one cationic peptide has passed phase III trials and shows equivalence to a quinolone against a localized infection, although there are several others under consideration. Unfortunately, there are few other new types of antibiotics close to clinical use, although there are many compounds that are under development (1). These include a small number of protein synthesis and cell wall inhibitors. Lipid A inhibitors are in early stages, and other drugs under development are derivatives of existing antibiotics (such as vancomycin). The lack of new types of antibiotics emphasizes the need to understand the mechanisms of bacterial pathogenicity, which can then be applied to developing new therapeutics. 1. R. E. W. Hancock, Clin. Inf. Dis. 24 (suppl. 1), S148 (1997). [1]: #ref-1 [2]: #xref-ref-1-1 View reference 1 in text [3]: {openurl}?query=rft.jtitle%253DLancet%26rft.stitle%253DLancet%26rft.aulast%253DHancock%26rft.auinit1%253DR.%2BE.%26rft.volume%253D349%26rft.issue%253D9049%26rft.spage%253D418%26rft.epage%253D422%26rft.atitle%253DPeptide%2Bantibiotics.%26rft_id%253Dinfo%253Adoi%252F10.1016%252FS0140-6736%252897%252980051-7%26rft_id%253Dinfo%253Apmid%252F9033483%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [4]: /lookup/external-ref?access_num=10.1016/S0140-6736(97)80051-7&link_type=DOI [5]: /lookup/external-ref?access_num=9033483&link_type=MED&atom=%2Fsci%2F277%2F5324%2F297.4.atom [6]: /lookup/external-ref?access_num=A1997WH29600048&link_type=ISI [7]: {openurl}?query=rft.jtitle%253DFEBS%2BLetters%26rft.stitle%253DFEBS%2BLetters%26rft.aulast%253DBoman%26rft.auinit1%253DH.%2BG.%26rft.volume%253D259%26rft.issue%253D1%26rft.spage%253D103%26rft.epage%253D106%26rft.atitle%253DAntibacterial%2Band%2Bantimalarial%2Bproperties%2Bof%2Bpeptides%2Bthat%2Bare%2Bcecropin-melittin%2Bhybrids.%26rft_id%253Dinfo%253Adoi%252F10.1016%252F0014-5793%252889%252981505-4%26rft_id%253Dinfo%253Apmid%252F2689223%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [8]: /lookup/external-ref?access_num=10.1016/0014-5793(89)81505-4&link_type=DOI [9]: /lookup/external-ref?access_num=2689223&link_type=MED&atom=%2Fsci%2F277%2F5324%2F297.4.atom [10]: /lookup/external-ref?access_num=A1989CF90200026&link_type=ISI

Aim and Background:Antibiotic resistance currently spans most of the known classes of natural and synthetic antibiotics; limiting our options for treatment of infections and demanding discovery of new classes of antibiotics. Much effort is being directed towards developing new antibiotics to overcome this problem. Success in getting novel chemical entities from microbial sources depends essentially on novelty of its habitat. The diversity of geographical location decides the type of micro-flora. In the past various terrestrial and aqueous microorganisms have provided several novel bioactive secondary metabolites of pharmaceutical importance. Hot-springs have not been as extensively exploited as other terrestrial resources. However, perseverance with such microbes augment the probability of getting novel bioactive compounds.Materials and Methods:Hot-springs soil samples were collected from Hot-springs in Maharashtra. Actinomycetes and other eubacteria were isolated from these soil samples by selective methods and purified. They were classified based on gram's nature and morphology. Six representative morphological strains were screened for their anti-infective potential by agar well diffusion method as reported by Nathan P. et al (1974). The bioactivity of the active microbes was confirmed.Results:Seventy three strains of bacteria encompassing eight actinomycetes, and 65 eubacteria were isolated and purified. Among the actives eubacteria PPVWK106001 showed broad spectrum antibacterial activity encompassing both gram positive and gram negative bacterial test models. The extract was active against resistant bacteria such as MRSA and VREs. Activity was very specific as there was no activity against fungi even at 100 fold concentration. The active principle was extractable in butanol.Conclusions:The study showed that Hot-springs exhibit diverse bacteria and it serves as potential reservoirs for bacteria of antimicrobial importance with diverse facet of activities. Thus Hot-springs microbes have ability to address issue of resistant bugs.

The value of nature's natural product library for the discovery of New Chemical Entities: The discovery of ingenol mebutate

P-348 - Developing a new class of antibiotics – a step closer

The alarming rise of multidrug-resistant Gram-positive bacteria has precipitated a healthcare crisis, necessitating the development of new antimicrobial therapies. Here we describe a new class of antibiotics based on a ring-fused 2-pyridone backbone, which are active against vancomycin-resistant enterococci (VRE), a serious threat as classified by the Centers for Disease Control and Prevention, and other multidrug-resistant Gram-positive bacteria. Ring-fused 2-pyridone antibiotics have bacteriostatic activity against actively dividing exponential phase enterococcal cells and bactericidal activity against nondividing stationary phase enterococcal cells. The molecular mechanism of drug-induced killing of stationary phase cells mimics aspects of fratricide observed in enterococcal biofilms, where both are mediated by the Atn autolysin and the GelE protease. In addition, combinations of sublethal concentrations of ring-fused 2-pyridones and standard-of-care antibiotics, such as vancomycin, were found to synergize to kill clinical strains of VRE. Furthermore, a broad range of antibiotic resistant Gram-positive pathogens, including those responsible for the increasing incidence of antibiotic resistant healthcare-associated infections, are susceptible to this new class of 2-pyridone antibiotics. Given the broad antibacterial activities of ring-fused 2-pyridone compounds against Gram-positive (GmP) bacteria we term these compounds GmPcides, which hold promise in combating the rising tide of antibiotic resistant Gram-positive pathogens.

Two hetero-tri-organometallic compounds with potent activity against Gram-positive bacteria including multi-resistant Staphylococcus aureus (MRSA) were identified. The compounds consist of a peptide nucleic acid backbone with an alkyne side chain, substituted with a cymantrene, a (dipicolyl)Re(CO)3 moiety, and either a ferrocene (FcPNA) or a ruthenocene (RcPNA). Comparative proteomic analysis indicates the bacterial membrane as antibiotic target structure. FcPNA accumulation in the membrane was confirmed by manganese tracing with atomic absorption spectroscopy. Both organometallics disturbed several essential cellular processes taking place at the membrane such as respiration and cell wall biosynthesis, suggesting that the compounds affect membrane architecture. Correlating with enhanced antibacterial activity, oxidative stress was induced only by the ferrocene-substituted compound. The organometallics described here target the cytoplasmic membrane, a clinically proven antibacterial target structure, feature a bactericidal but non-bacteriolytic mode of action and limited cytotoxicity within the limits of solubility. Thus, FcPNA represents a promising lead structure for the development of a new synthetic class of antibiotics.

Researchers have discovered a new class of potential antibiotics that work against methicillin-resistant Staphylococcus aureus (MRSA) and against so-called persisters, dormant bacteria associated with chronic infections (Nature 2018, DOI: 10.1038/nature26157). The team, led by Eleftherios Mylonakis of Brown University, Rhode Island Hospital, and Miriam Hospital, screened a library of small molecules to find ones that decrease MRSA’s ability to kill Caenorhabditis elegans, a model organism. From this screen, the researchers identified two synthetic retinoids known as CD437 and CD1530 as potential antibacterial compounds. When incubated with those compounds for two hours, the MRSA strain MW2 dropped below the limit of detection. When the researchers exposed the bacteria to elevated retinoid concentrations, they did not find any MW2 that had mutated to survive the treatments. And after 100 days of growing MW2 in doses of CD437 below the compound’s minimum inhibitory concentration, the researchers identified ...

Parp-1 and Parp-2 are activated by DNA breaks and have been implicated in the repair of DNA single-strand breaks (SSB). Their involvement in double-strand break (DSB) repair mediated by homologous recombination (HR) or nonhomologous end joining (NHEJ) remains unclear. We addressed this question using chicken DT40 cells, which have the advantage of carrying only a PARP-1 gene but not a PARP-2 gene. We found that PARP-1(-/-) DT40 mutants show reduced levels of HR and are sensitive to various DSB-inducing genotoxic agents. Surprisingly, this phenotype was strictly dependent on the presence of Ku, a DSB-binding factor that mediates NHEJ. PARP-1/KU70 double mutants were proficient in the execution of HR and displayed elevated resistance to DSB-inducing drugs. Moreover, we found deletion of Ligase IV, another NHEJ gene, suppressed the camptothecin of PARP-1(-/-) cells. Our results suggest a new critical function for Parp in minimizing the suppressive effects of Ku and the NHEJ pathway on HR.