Characterization, mechanism of action and optimization of activity of a novel peptide-peptoid hybrid against bacterial pathogens involved in canine skin infections

Abstract

Integumentary infections like pyoderma represent the main reason for antimicrobial prescription in dogs. Staphylococcus pseudintermedius and Pseudomonas aeruginosa are frequently identified in these infections, and both bacteria are challenging to combat due to resistance. To avoid use of important human antibiotics for treatment of animal infections there is a pressing need for novel narrow-spectrum antimicrobial agents in veterinary medicine. Herein, we characterize the in vitro activity of the novel peptide-peptoid hybrid B1 against canine isolates of S . pseudintermedius and P . aeruginosa . B1 showed potent minimum inhibitory concentrations (MICs) against canine S . pseudintermedius and P . aeruginosa isolates as well rapid killing kinetics. B1 was found to disrupt the membrane integrity and affect cell-wall synthesis in methicillin-resistant S . pseudintermedius (MRSP). We generated 28 analogues of B1 , showing comparable haemolysis and MICs against MRSP and P . aeruginosa . The most active analogues ( 23 , 26 ) and B1 were tested against a collection of clinical isolates from canine, of which only B1 showed potent activity. Our best compound 26 , displayed activity against P . aeruginosa and S . pseudintermedius , but not the closely related S . aureus . This work shows that design of target-specific veterinary antimicrobial agents is possible, even species within a genus, and deserves further exploration.

Correlation between hemolytic activity, cytotoxicity and systemic in vivo toxicity of synthetic antimicrobial peptides

“…The haemolytic activity against human, dog and rat is correlated to peptide hydrophobicity, with inactive compounds such as 3-5 and 8 and 9 also being the most polar ones in the study. These compounds were also shown in our previous study to display no haemolytic activity against human erythrocytes 29 . More haemolytic compounds such as 6, 11, 15, 18 and 19 are also generally more hydrophobic, a property also evident in the antimicrobial effect of this type of compounds which is driven by both charge and hydrophobicity 17 .…”

“…The antimicrobial activity against Gram-positive and Gram-negative bacteria and preliminary human haemolysis of the compounds has been recently reported 29 . The compounds were synthesised using Fmoc solid phase peptide or a combination of solid phase peptide synthesis and sub-monomer peptoid synthesis (2, 14, 15 and 23) as previously described 29 . The compounds and their antimicrobial activity are reported in Table 1.…”

“…With these considerations in mind, our present study aims to be a step towards filling the existing knowledge gap between in vitro toxicity screening and effect observed in vivo by providing a toxicity profile for a series of promising narrow spectrum AMPs incorporating unnatural amino acids and peptoid elements 29 in an attempt to assess the correlation between haemolytic activity, intra-species variation, cytotoxicity and in vivo data (displayed in Fig. 1 and Table 1 and tabulated in Table S1-S4).…”

“…1 and Table 1 and tabulated in Table S1-S4). The peptide library evaluated contain promising narrow-spectrum antimicrobial agents towards integumentary infections and they range from highly active to inactive providing a relevant spread in physicochemical properties 29 . The study includes a comparative study of the haemolytic activity between human, dog, rat and bovine donors.…”

Structure-Activity Study of an All-d Antimicrobial Octapeptide D2D

“…The manual Fmoc solid-phase synthesis of peptides was carried out in disposable syringes, equipped with a fritted filter [31]. Crude products were purified by preparative RP-HPLC until ≥95% purity was obtained (analytical RP-HPLC).…”