Bacterial resistance is eroding the clinical utility of existing antibiotics necessitating the discovery of new agents. Bacterial type II topoisomerase is a clinically validated, highly effective, and proven drug target. This target is amenable to inhibition by diverse classes of inhibitors with alternative and distinct binding sites to quinolone antibiotics, thus enabling the development of agents that lack cross-resistance to quinolones. Described here are novel bacterial topoisomerase inhibitors (NBTIs), which are a new class of gyrase and topo IV inhibitors and consist of three distinct structural moieties. The substitution of the linker moiety led to discovery of potent broad-spectrum NBTIs with reduced off-target activity (hERG IC 50 > 18 μM) and improved physical properties. AM8191 is bactericidal and selectively inhibits DNA synthesis and Staphylococcus aureus gyrase (IC 50 = 1.02 μM) and topo IV (IC 50 = 10.4 μM). AM8191 showed parenteral and oral efficacy (ED 50 ) at less than 2.5 mg/kg doses in a S. aureus murine infection model. A cocrystal structure of AM8191 bound to S. aureus DNA-gyrase showed binding interactions similar to that reported for GSK299423, displaying a key contact of Asp83 with the basic amine at position-7 of the linker.
Methicillin-resistant Staphylococcus aureus (MRSA) is a major nosocomial and community-acquired pathogen for which few existing antibiotics are efficacious. Here we describe two structurally related synthetic compounds that potentiate beta-lactam activity against MRSA. Genetic studies indicate that these agents target SAV1754 based on the following observations: (i) it has a unique chemical hypersensitivity profile, (ii) overexpression or point mutations are sufficient to confer resistance, and (iii) genetic inactivation phenocopies the potentiating effect of these agents in combination with beta-lactams. Further, we demonstrate these agents inhibit peptidoglycan synthesis. Because SAV1754 is essential for growth and structurally related to the recently reported peptidoglycan flippase of Escherichia coli, we speculate it performs an analogous function in S. aureus. These results suggest that SAV1754 inhibitors might possess therapeutic potential alone, or in combination with beta-lactams to restore MRSA efficacy.
The availability of genome sequences is revolutionizing the field of microbiology. Genetic methods are being modified to facilitate rapid analysis at a genome-wide level and are blossoming for human pathogens that were previously considered intractable. This revolution coincided with a growing concern about the emergence of microbial drug resistance, compelling the pharmaceutical industry to search for new antimicrobial agents. The availability of the new technologies, combined with many genetic strategies, has changed the way that researchers approach antibacterial drug discovery.
Background: LpxC is a metal-dependent deacetylase essential for lipopolysaccharide biosynthesis. Results: The LpxC reaction product binds an extensive, conserved groove with the 2-amino group positioned in the active site. Conclusion: The product-bound LpxC structure reveals conserved ligand interactions and stabilization of a phosphate mimic of the oxyanion intermediate. Significance: LpxC structures are critical to elucidate the catalytic mechanism and design of novel antibiotics.
Isoniazid (INH) is a highly effective drug used in the treatment and prophylaxis of Mycobacterium tuberculosis infections. Resistance to INH in clinical isolates has been correlated with mutations in the inhA, katG, andahpC genes. In this report, we describe a new mechanism for INH resistance in Mycobacterium smegmatis. Mutations that reduce NADH dehydrogenase activity (Ndh; type II) cause multiple phenotypes, including (i) coresistance to INH and a related drug, ethionamide; (ii) thermosensitive lethality; and (iii) auxotrophy. These phenotypes are corrected by expression of one of two enzymes: NADH dehydrogenase and the NADH-dependent malate dehydrogenase of theM. tuberculosis complex. The genetic data presented here indicate that defects in NADH oxidation cause all of the mutant traits and that an increase in the NADH/NAD+ ratio confers INH resistance.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.