Elucidation of the Active Conformation of Vancomycin Dimers with Antibacterial Activity against Vancomycin-Resistant Bacteria

Conformations and Rearrangements of Collinolactone - Experiments and Theory on a Dynamic Cyclodecatriene

Collinolactone A is a microbial specialized metabolite with a unique 6-10-7 tricyclic bislactone skeleton which was isolated from Streptomyces bacteria. The unusual cyclodecatriene motif features dynamic interconversions of two rotamers. Given the biological profiling of collinolactone A as neuroprotective agent, semisynthetic modifications represent an invaluable strategy to enhance its efficacy. Since understanding conformations and reactions of bioactive substances is crucial for rational structure-based design and synthesis of derivatives, we conducted computational studies on conformational behavior as well as experiments on thermal and acid induced rearrangements of the cyclodecatriene. Experimental conformer ratios of collinolactone A and its biosynthetic ketolactone precursor are well reproduced by computations at the PW6B95-D3/def2-QZVPP//r2 SCAN-3c level. Upon heating collinolactone A in anhydrous dioxane at 100 °C, three collinolactone B stereoisomers exhibiting enollactone structures form via Cope rearrangements. Our computations predict the energetic preference for a boat-like transition state in agreement with the stereochemical outcome of the main reaction pathway. Constriction of the ten-membered ring forms collinolactone C with four annulated rings and an exocyclic double bond. Computations and semisynthetic experiments demonstrate strong preference for an acid-catalyzed reaction pathway over an alternative Alder-ene route to collinolactone C with a prohibitive reaction barrier, again in line with stereochemical observations.

Regulation of Resistance in Vancomycin-Resistant Enterococci: The VanRS Two-Component System

Vancomycin-resistant enterococci (VRE) are a serious threat to human health, with few treatment options being available. New therapeutics are urgently needed to relieve the health and economic burdens presented by VRE. A potential target for new therapeutics is the VanRS two-component system, which regulates the expression of vancomycin resistance in VRE. VanS is a sensor histidine kinase that detects vancomycin and in turn activates VanR; VanR is a response regulator that, when activated, directs expression of vancomycin-resistance genes. This review of VanRS examines how the expression of vancomycin resistance is regulated, and provides an update on one of the field's most pressing questions: How does VanS sense vancomycin?

Alternatives to Fight Vancomycin-Resistant Staphylococci and Enterococci

Gram positive pathogens are a significant cause of healthcare-associated infections, with Staphylococci and Enterococci being the most prevalent ones. Vancomycin, a last resort glycopeptide, is used to fight these bacteria but the emergence of resistance against this drug leaves some patients with few therapeutic options. To counter this issue, new generations of antibiotics have been developed but resistance has already been reported. In this article, we review the strategies in place or in development to counter vancomycin-resistant pathogens. First, an overview of traditional antimicrobials already on the market or in the preclinical or clinical pipeline used individually or in combination is summarized. The second part focuses on the non-traditional antimicrobials, such as antimicrobial peptides, bacteriophages and nanoparticles. The conclusion is that there is hitherto no substitute equivalent to vancomycin. However, promising strategies based on drugs with multiple mechanisms of action and treatments based on bacteriophages possibly combined with conventional antibiotics are hoped to provide treatment options for vancomycin-resistant Gram-positive pathogens.

N-doped carbon nanosheets with antibacterial activity: mechanistic insight

Carbon nanosheets with sharp “knife-like” edges interact with an E. coli bacterial membrane resulting in cell death.

Binding properties of antimicrobial agents to dipeptide terminal of lipid II using surface plasmon resonance

We developed a surface plasmon resonance (SPR) assay to estimate the interactions of antimicrobial agents with the dipeptide terminal of lipid II (D-alanyl-D-alanine) and its analogous dipeptides (L-alanyl-L-alanine and D-alanyl-D-lactate) as ligands. The established SPR method showed the reproducible immobilization of ligands on sensor chip and analysis of binding kinetics of antimicrobial agents to ligands. The ligand-immobilized chip could be used repeatedly for at least 200 times for the binding assay of antimicrobial agents, indicating that the ligand-immobilized chip is sufficiently robust for the analysis of binding kinetics. In this SPR system, the selective and specific binding characteristics of vancomycin and its analogs to the ligands were estimated and the kinetic parameters were calculated. The kinetic parameters revealed that one of the remarkable binding characteristics was the specific interaction of vancomycin to only the D-alanyl-D-alanine ligand. In addition, the kinetic binding data of SPR showed close correlation with the antimicrobial activity. The SPR data of other antimicrobial agents (e.g., teicoplanin) to the ligands showed correlation with the antimicrobial activity on the basis of the therapeutic mechanism. Our SPR method could be a valuable tool for predicting the binding characteristics of antimicrobial agents to the dipeptide terminal of lipid II.