gentamicin-sulfate and Hemolysis

We report on the first chemical syntheses and structure-activity analyses of the cyclic lipopeptide battacin which revealed that conjugation of a shorter fatty acid, 4-methyl-hexanoic acid, and linearization of the peptide sequence improves antibacterial activity and reduces hemolysis of mouse blood cells. This surprising finding of higher potency in linear lipopeptides than their cyclic counterparts is economically beneficial. This novel lipopeptide was membrane lytic and exhibited antibiofilm activity against Pseudomonas aeruginosa, Staphylococcus aureus, and, for the first time, Pseudomonas syringe pv. actinidiae. The peptide was unstructured in aqueous buffer and dimyristoylphosphatidylcholine-polymerized diacetylene vesicles, with 12% helicity induced in 50% v/v of trifluoroethanol. Our results indicate that a well-defined secondary structure is not essential for the observed antibacterial activity of this novel lipopeptide. A truncated pentapeptide conjugated to 4-methyl hexanoic acid, having similar potency against Gram negative and Gram positive pathogens was identified through alanine scanning.

Topics: Animals; Anti-Bacterial Agents; Bacteria; Biofilms; Cell Membrane Permeability; Hemolysis; Lipopeptides; Magnetic Resonance Spectroscopy; Mice; Microbial Sensitivity Tests; Structure-Activity Relationship

Treating infections caused by multidrug-resistant Gram-negative pathogens is challenging, and there is concern regarding the toxicity of the most effective antimicrobials for Gram-negative pathogens. We hypothesized that conjugating a fatty acid moiety onto a peptide dimer could maximize the interaction with lipopolysaccharide (LPS) and facilitate the permeabilization of the LPS barrier, thereby improving potency against Gram-negative pathogens. We systematically designed a series of N-lipidated peptide dimers that are active against Gram-negative bacteria, including carbapenem-resistant Enterobacteriaceae (CRE). The optimized lipid length was 6-10 carbons. At these lipid lengths, the N-lipidated peptide dimers exhibited strong LPS permeabilization. Compound 23 exhibited synergy with select antibiotics in most of the combinations tested. 23 and 32 also displayed rapid bactericidal activity. Importantly, 23 and 32 were nonhemolytic at 10 mg/mL, with no cellular or in vivo toxicity. These characteristics suggest that these compounds can overcome the limitations of current Gram-negative-targeted antimicrobials such as polymyxin B.

Topics: Animals; Anti-Bacterial Agents; Carbapenems; Cell Membrane; Cell Survival; Drug Resistance, Bacterial; Enterobacteriaceae; Fatty Acids; Female; Fibroblasts; Gram-Negative Bacteria; Hemolysis; Humans; In Vitro Techniques; L-Lactate Dehydrogenase; Lipopeptides; Lipopolysaccharides; Male; Mice; Microbial Sensitivity Tests; Permeability; Rabbits

There is a great urgency in developing a new generation of antibiotics and antimicrobial agents since the bacterial resistance to antibiotics have increased dramatically. A series of overlapped peptide fragments of Ixosin-B, an antimicrobial peptide with amino acid sequence of QLKVDLWGTRSGIQPEQHSSGKSDVRRWRSRY, was designed, synthesized and examined for their antimicrobial activities against Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa. A potent 11-mer peptide TSG-8-1, WWSYVRRWRSR-amide, was developed, which exhibited antimicrobial activity against E. coli and S. aureus while very little hemolytic activity in human erythrocytes was observed at high dose level. This peptide could be further modified for the development of a potent antimicrobial agent in the future.

Topics: Anti-Bacterial Agents; Antimicrobial Cationic Peptides; Arthropod Proteins; Dose-Response Relationship, Drug; Erythrocytes; Escherichia coli; Hemolysis; Humans; Microbial Sensitivity Tests; Oligopeptides; Pseudomonas aeruginosa; Staphylococcus aureus; Structure-Activity Relationship

We investigated the potency, selectivity, and mode of action of the oligo-acyl-lysine (OAK) NC(12)-2 beta(12), which was recently suggested to represent the shortest OAK sequence that retains nonhemolytic antibacterial properties. A growth inhibition assay against a panel of 48 bacterial strains confirmed that NC(12)-2 beta(12) exerted potent activity against gram-positive bacteria while exhibiting negligible hemolysis up to at least 100 times the MIC. Interestingly, NC(12)-2 beta(12) demonstrated a bacteriostatic mode of action, unlike previously described OAKs that were bactericidal and essentially active against gram-negative bacteria only. The results of various experiments with binding to model phospholipid membranes correlated well with those of the cytotoxicity experiments and provided a plausible explanation for the observed activity profile. Thus, surface plasmon resonance experiments performed with model bilayers revealed high binding affinity to a membrane composition that mimicked the plasma membrane of staphylococci (global affinity constant [K(app)], 3.7 x 10(6) M(-1)) and significantly lower affinities to mimics of Escherichia coli or red blood cell cytoplasmic membranes. Additional insertion isotherms and epifluorescence microscopy experiments performed with model Langmuir monolayers mimicking the outer leaflet of plasma membranes demonstrated the preferential insertion of NC(12)-2 beta(12) into highly anionic membranes. Finally, we provide mechanistic studies in support of the view that the bacteriostatic effect resulted from a relatively slow process of plasma membrane permeabilization involving discrete leakage of small solutes, such as intracellular ATP. Collectively, the data point to short OAKs as a potential source for new antibacterial compounds that can selectively affect the growth of gram-positive bacteria while circumventing potential adverse effects linked to lytic compounds.

Topics: Anti-Bacterial Agents; Antimicrobial Cationic Peptides; Cell Membrane; Erythrocytes; Escherichia coli; Gram-Positive Bacteria; Hemolysis; Humans; Microscopy, Fluorescence; Staphylococcus; Surface Plasmon Resonance

Series of short amino terminal modified cationic peptides were designed and synthesized. All of the synthesized compounds were tested against gram-positive as well as gram-negative bacterial strain. Some of the compounds exhibit potent antibacterial activity and no hemolytic activity even at high dose level (1000 microg/mL) in mammalian erythrocytes was observed.

Topics: Anti-Bacterial Agents; Gram-Positive Bacteria; Hemolysis; Humans; Microbial Sensitivity Tests; Peptides