title: In vitro activity of novel in silico-developed antimicrobial peptides against a panel of bacterial pathogens.
abstract: Antimicrobial-peptide-based therapies could represent a reliable alternative to overcome antibiotic resistance, as they offer potential advantages such as rapid microbicidal activity and multiple activities against a broad spectrum of bacterial pathogens. Three synthetic antimicrobial peptides (AMPs), AMP72, AMP126, and also AMP2041, designed by using ad hoc screening software developed in house, were synthesized and tested against nine reference strains. The peptides showed a partial β-sheet structure in 10-mM phosphate buffer. Low cytolytic activity towards both human cell lines (epithelial, endothelial, and fibroblast) and sheep erythrocytes was observed for all peptides. The antimicrobial activity was dose dependent with a minimum bactericidal concentration (MBC) ranging from 0.17 to 10.12 μM (0.4-18.5 µg/ml) for Gram-negative and 0.94 to 20.65 μM (1.72-46.5 µg/ml) for Gram-positive bacteria. Interestingly, in high-salt environment, the antibacterial activity was generally maintained for Gram-negative bacteria. All peptides achieved complete bacterial killing in 20 min or less against Gram-negative bacteria. A linear time-dependent membrane permeabilization was observed for the tested peptides at 12.5 µg/ml. In a medium containing Mg²⁺ and Ca²⁺, the peptide combination with EDTA restores the antimicrobial activity particularly for AMP2041. Moreover, in combination with anti-infective agents (quinolones or aminoglycosides) known to bind divalent cation, AMP126 and AMP2041 showed additive activity in comparison with colistin. Our results suggest the following: (i) there is excellent activity against Gram-negative bacteria, (ii) there is low cytolytic activity, (iii) the presence of a chelating agent restores the antimicrobial activity in a medium containing Mg²⁺ and Ca²⁺, and (iv) the MBC value of the combination AMPs-conventional antibiotics was lower than the MBC of single agents alone.
authors.affiliation: Dipartimento di Medicina Clinica e Sperimentale, Università di Parma, Parma, Italy.
authors.forename: A A
authors.initials: AA
authors.lastname: Romani
authors.forename: M C
authors.initials: MC
authors.lastname: Baroni
authors.forename: S
authors.initials: S
authors.lastname: Taddei
authors.forename: F
authors.initials: F
authors.lastname: Ghidini
authors.forename: P
authors.initials: P
authors.lastname: Sansoni
authors.forename: S
authors.initials: S
authors.lastname: Cavirani
authors.forename: C S
authors.initials: CS
authors.lastname: Cabassi
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000494:pharmacology*; D023181:Antimicrobial Cationic Peptides / Q000737:chemistry / Q000494:pharmacology*; D002460:Cell Line; D002463:Cell Membrane Permeability; D002614:Chelating Agents / Q000494:pharmacology; D003198:Computer Simulation; D004357:Drug Synergism; D004492:Edetic Acid / Q000494:pharmacology; D004912:Erythrocytes / Q000187:drug effects; D006090:Gram-Negative Bacteria / Q000187:drug effects; D006094:Gram-Positive Bacteria / Q000187:drug effects; D061307:Human Umbilical Vein Endothelial Cells / Q000187:drug effects; D006801:Humans; D008826:Microbial Sensitivity Tests; D008956:Models, Chemical; D008969:Molecular Sequence Data; D016571:Neural Networks, Computer; D012372:ROC Curve; D034561:Sheep, Domestic
chemical_list: D000900:Anti-Bacterial Agents; D023181:Antimicrobial Cationic Peptides; D002614:Chelating Agents; D004492:Edetic Acid
keywords: antimicrobial activity; antimicrobial peptides; combined therapy; cytoplasmic membrane permeabilization; hemolysis