No abstract

New Delhi metallo-β-lactamase-1 (NDM-1) is the most prevalent type of metallo-β-lactamase and hydrolyzes almost all clinically used β-lactam antibiotics. Here we show that the antimicrobial peptide thanatin disrupts the outer membrane of NDM-1-producing bacteria by competitively displacing divalent cations on the outer membrane and inducing the release of lipopolysaccharides. In addition, thanatin inhibits the enzymatic activity of NDM-1 by displacing zinc ions from the active site, and reverses carbapenem resistance in NDM-1-producing bacteria in vitro and in vivo. Thus, thanatin’s dual mechanism of action may be useful for combating infections caused by NDM-1-producing pathogens.

No abstract

BackgroundMethicillin-resistant Staphylococcus aureus (MRSA) causes threatening infection-related mortality worldwide. Currently, spread of multi-drug resistance (MDR) MRSA limits therapeutic options and requires new approaches to “druggable” target discovery, as well as development of novel MRSA-active antibiotics. RNA polymerase primary σ70 (encoded by gene rpoD) is a highly conserved prokaryotic factor essential for transcription initiation in exponentially growing cells of diverse S. aureus, implying potential for antisense inhibition.Methodology/Principal FindingsBy synthesizing a serial of cell penetrating peptide conjugated peptide nucleic acids (PPNAs) based on software predicted parameters and further design optimization, we identified a target sequence (234 to 243 nt) within rpoD mRNA conserved region 3.0 being more sensitive to antisense inhibition. A (KFF)3K peptide conjugated 10-mer complementary PNA (PPNA2332) was developed for potent micromolar-range growth inhibitory effects against four pathogenic S. aureus strains with different resistance phenotypes, including clinical vancomycin-intermediate resistance S. aureus and MDR-MRSA isolates. PPNA2332 showed bacteriocidal antisense effect at 3.2 fold of MIC value against MRSA/VISA Mu50, and its sequence specificity was demonstrated in that PPNA with scrambled PNA sequence (Scr PPNA2332) exhibited no growth inhibitory effect at higher concentrations. Also, PPNA2332 specifically interferes with rpoD mRNA, inhibiting translation of its protein product σ70 in a concentration-dependent manner. Full decay of mRNA and suppressed expression of σ70 were observed for 40 µM or 12.5 µM PPNA2332 treatment, respectively, but not for 40 µM Scr PPNA2332 treatment in pure culture of MRSA/VISA Mu50 strain. PPNA2332 (≥1 µM) essentially cleared lethal MRSA/VISA Mu50 infection in epithelial cell cultures, and eliminated viable bacterial cells in a time- and concentration- dependent manner, without showing any apparent toxicity at 10 µM.ConclusionsThe present result suggested that RNAP primary σ70 is a very promising candidate target for developing novel antisense antibiotic to treat severe MRSA infections.

Abstract. The treatment of septicemia caused by antibiotic-resistant bacteria is a great challenge in the clinic. Because traditional antibiotics inevitably induce bacterial resistance, which is responsible for many treatment failures, there is an urgent need to develop novel antibiotic drugs. Amino-terminated Poly (amidoamine) dendrimers (PAMAM-NH 2 ) are reported to have antibacterial activities. However, previous studies focused on high generations of PAMAM-NH 2 , which have been found to exhibit high toxicities. The present study aimed to clarify whether low generations of PAMAM-NH 2 could be used as novel antibacterial agents. We found that generation 2 (G2.0) PAMAM-NH 2 showed significant antibacterial effects against antibiotic-sensitive and antibiotic-resistant strains but exhibited little toxicity to human gastric epithelial cells and did not induce antibiotic resistance in bacteria. Scanning and transmission electron microscopy analyses suggested that G2.0 PAMAM-NH 2 might inhibit the growth of bacteria by destroying their cell membranes. The administration of G2.0 PAMAM-NH 2 dosedependently improved the animal survival rate of mice infected with extended-spectrum beta lactamase-producing Escherichia coli (ESBL-EC) and of animals infected with a combination of ESBL-EC and methicillin-resistant Staphylococcus aureus. A treatment regimen of 10 mg/kg of G2.0 PAMAM-NH 2 starting 12 h before inoculation followed by 10 mg/kg at 0.5 h after inoculation rescued 100% of singly infected mice and 60% of multiply infected mice. The protective effects were associated with the reduction of the bacterial titers in the blood and with the morphological amelioration of infected tissues. These findings demonstrate that the G2.0 PAMAM-NH 2 is a potential broad-spectrum and nonresistance-inducing antibiotic agent with relatively low toxicity.

b Methicillin-resistant Staphylococcus aureus (MRSA) infections are becoming increasingly difficult to treat, owing to acquired antibiotic resistance. The emergence and spread of MRSA limit therapeutic options and require new therapeutic strategies, including novel MRSA-active antibiotics. Filamentous temperature-sensitive protein Z (FtsZ) is a highly conserved bacterial tubulin homologue that is essential for controlling the bacterial cell division process in different species of S. aureus. We conjugated a locked nucleic acid (LNA) that targeted ftsZ mRNA with the peptide (KFF) 3 K, to generate peptide-LNA (PLNA). The present study aimed to investigate whether PLNA could be used as a novel antibacterial agent. PLNA787, the most active agent synthesized, exhibited promising inhibitory effects on four pathogenic S. aureus strains in vitro. PLNA787 inhibited bacterial growth and resolved lethal Mu50 infections in epithelial cell cultures. PLNA787 also improved the survival rates of Mu50-infected mice and was associated with reductions of bacterial titers in several tissue types. The inhibitory effects on ftsZ mRNA and FtsZ protein expression and inhibition of the bacterial cell division process are considered to be the major mechanisms of PLNA. PLNA787 demonstrated activity against MRSA infections in vitro and in vivo. Our findings suggest that ftsZ mRNA is a promising new target for developing novel antisense antibiotics. Staphylococcus aureus, particularly methicillin-resistant S. aureus (MRSA), is one of the most prominent pathogens known to pose a severe threat to human health (1). Statistical data from recent epidemiological studies indicate that the prevalence of MRSA is spreading globally. MRSA, particularly community-associated MRSA, has increased markedly in prevalence and continues to pose a significant public health challenge (2-4). ␤-Lactam antibiotics are most effective against infections caused by S. aureus. However, widespread use of ␤-lactam antibiotics has led to increasing prevalence of drug-resistant S. aureus; thus, the therapeutic options available for treating MRSA infections have become seriously limited, and MRSA infections are becoming increasingly difficult to treat. Indeed, MRSA has become resistant to the entire class of ␤-lactam antibiotics and to most available antibiotics (5-7). Although linezolid, daptomycin, and telavancin are new drugs to treat MRSA infections, the development of new and non-cross-resistant antibacterial agents with novel mechanisms of action against MRSA is still needed.Antisense oligonucleotides are potential therapeutic agents for prevention of the translation of essential genes at the mRNA level with antisense nucleic acid analogues, such as phosphorothioate oligodeoxynucleotides (PS-ODNs), peptide-nucleic acids (PNAs), locked nucleic acids (LNAs), and phosphorodiamidate morpholino oligomers (8, 9). LNAs are nucleic acid analogues in which the ribose ring is locked by a 2=-O,4=-C-methylene bridge. LNA oligomers have high affinity for RNA or DNA targets, are qu...

As a flavin adenine dinucleotide (FAD)-dependent monoamine oxidase, lysine specific demethylase 1 (LSD1/KDM1A) functions as a transcription coactivator or corepressor to regulate the methylation of histone 3 lysine 4 and 9 (H3K4/9), and it has emerged as a promising epigenetic target for anticancer treatment. To date, numerous inhibitors targeting LSD1 have been developed, some of which are undergoing clinical trials for cancer therapy. Although only two reversible LSD1 inhibitors CC-90011 and SP-2577 are in the clinical stage, the past decade has seen remarkable advances in the development of reversible LSD1 inhibitors. Herein, we provide a comprehensive review about structures, biological evaluation, and structure–activity relationship (SAR) of reversible LSD1 inhibitors.

Because the development of multidrug resistance limits the available therapeutic options, A-thanatin may provide a novel strategy for treating ESBL-EC infection and other infections due to multidrug-resistant bacteria.