The threat of antibiotic resistance warrants the discovery of agents with novel antimicrobial mechanisms. Antimicrobial peptides (AMPs) directly disrupting bacterial membranes may overcome resistance to traditional antibiotics. AMP development for clinical use has been mostly limited to topical application to date. We developed a rational framework for systematically addressing this challenge using libraries composed of 86 novel Trp- and Arg-rich engineered peptides tested against clinical strains of the most common multidrug-resistant bacteria known as ESKAPE pathogens. Structure-function correlations revealed minimum lengths (as low as 16 residues) and Trp positioning for maximum antibacterial potency with mean minimum inhibitory concentration (MIC) of 2–4 μM and corresponding negligible toxicity to mammalian cells. Twelve peptides were selected based on broad-spectrum activity against both gram-negative and -positive bacteria and <25% toxicity to mammalian cells at maximum test concentrations. Most of the selected PAX remained active against the colistin-resistant clinical strains. Of the selected peptides, the shortest (the 16-residue E35) was further investigated for antibacterial mechanism and proof-of-concept in vivo efficacy. E35 killed an extensively-resistant isolate of Pseudomonas aeruginosa (PA239 from the CDC, also resistant to colistin) by irreversibly disrupting the cell membranes as shown by propidium iodide incorporation, using flow cytometry and live cell imaging. As proof of concept, in vivo toxicity studies showed that mice tolerated a systemic dose of up to 30 mg/kg peptide and were protected with a single 5 mg/kg intravenous (IV) dose against an otherwise lethal intraperitoneal injection of PA239. Efficacy was also demonstrated in an immune-compromised Klebsiella pneumoniae infection model using a daily dose of 4mg/kg E35 systemically for 2 days. This framework defines the determinants of efficacy of helical AMPs composed of only cationic and hydrophobic amino acids and provides a path for a potential departure from the restriction to topical use of AMPs toward systemic application.
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Caerin 1 Antimicrobial Peptides that Inhibit HIV and Neisseria May Spare Protective Lactobacilli
Although acquired immunodeficiency syndrome (AIDS) caused by the human immunodeficiency virus (HIV) is a manageable disease for many, it is still a source of significant morbidity and economic hardship for many others. The predominant mode of transmission of HIV/AIDS is sexual intercourse, and measures to reduce transmission are needed. Previously, we showed that caerin 1 antimicrobial peptides (AMPs) originally derived from Australian amphibians inhibited in vitro transmission of HIV at relatively low concentrations and had low toxicity for T cells and an endocervical cell line. The use of AMPs as part of microbicidal formulations would expose the vaginal microbiome to these agents and cause potential harm to protective lactobacilli. Here, we tested the effects of caerin 1 peptides and their analogs on the viability of two species of common vaginal lactobacilli (Lactobacillus rhamnosus and Lactobacillus crispatus). Several candidate peptides had limited toxicity for the lactobacilli at a range of concentrations that would inhibit HIV. Three AMPs were also tested for their ability to inhibit growth of Neisseria lactamica, a close relative of the sexually transmissible Neisseria gonorrhoeae. Neisseria lactamica was significantly more sensitive to the AMPs than the lactobacilli. Thus, several candidate AMPs have the capacity to inhibit HIV and possible N. gonorrhoeae transmission at concentrations that are significantly less harmful to the resident lactobacilli.
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- Award ID(s):
- 2011291
- NSF-PAR ID:
- 10288245
- Date Published:
- Journal Name:
- Antibiotics
- Volume:
- 9
- Issue:
- 10
- ISSN:
- 2079-6382
- Page Range / eLocation ID:
- 661
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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null (Ed.)Abstract Background Reducing Neisseria gonorrhoeae colonies in the oropharynx is a viable solution to minimize the transmission of this bacterium amongst individuals. Objectives A strategy involving the electrostatic interaction between a common antiseptic and a discontinued antibiotic (i.e. octenidine and carbenicillin) was evaluated as a potential treatment for gonorrhoea. Octenidine/carbenicillin is a novel group of uniform materials based on organic salts (GUMBOS) with inherent in vitro antibacterial activity that comes from its parent antiseptic and antibacterial ions, octenidine and carbenicillin, respectively. Methods Antibacterial activities for octenidine dihydrochloride, disodium carbenicillin, octenidine/carbenicillin and stoichiometrically equivalent 1:1 octenidine dihydrochloride to disodium carbenicillin were assessed using the Kirby–Bauer disc diffusion assay for N. gonorrhoeae (ATCC 49226) and three clinical isolates. Predictive permeability using the Parallel Artificial Membrane Permeability Assay and cytotoxicity against HeLa cells was also evaluated. Results Additive in vitro antibacterial activities against N. gonorrhoeae were observed in this study, which suggests octenidine/carbenicillin could be a useful agent in reducing N. gonorrhoeae transmission and minimizing gonorrhoea infections. Octenidine/carbenicillin also exhibited bioequivalence to azithromycin and doxycycline, two currently prescribed antibiotics. Likewise, octenidine/carbenicillin had improved predicted permeability compared with octenidine dihydrochloride. Conclusions Antimicrobial GUMBOS synthesized in this study could be used as an adjunctive treatment approach to current drug therapies for oropharyngeal gonorrhoea infection control and prevention.more » « less
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Antibiotics are losing effectiveness as bacteria become resistant to conventional drugs. To find new alternatives, antimicrobial peptides (AMPs) are rationally designed with different lengths, charges, hydrophobicities (
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.3390/antibiotics9100661
