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In Vitro Efficiency of Antimicrobial Peptides against Staphylococcal Pathogens Associated with Canine Pyoderma

Simple Summary

Coagulase-positive staphylococci (CoPS) are predominant pathogens in canine pyoderma, especially S. pseudintermedius and S. aureus. The antimicrobial resistance of CoPS has a key role in the management of canine skin infections. The vast majority of those diseases have a chronic character with a tendency to recur, which is reflected by recurrent systemic antibiotic therapy, associated with an alarming increase in the proportion of antibiotic-resistant staphylococci. Antimicrobial peptides (AMPs) seem to be a promising alternative to conventional antibiotics. The aim of this in vitro study was to evaluate the antimicrobial activity of selected AMPs against pathogenic staphylococcal strains, including multidrug- and methicillin-resistant strains isolated from canine pyoderma cases. The tested AMPs were shown to be equally efficient antimicrobial agents against resistant- and susceptible pathogenic staphylococcal strains associated with canine pyoderma. AMPs were more efficient against S. pseudintermedius than against S. aureus strains. Our findings seem to be particularly interesting from a clinical perspective, as a starting point from which to perform in vivo experiments to estimate the usefulness of these peptides as topical drug molecules for the treatment of canine pyoderma.

Abstract

The emergence of staphylococcal canine pathogens resistant to multiple antimicrobial agents is a growing and urgent problem in veterinary practice. Antimicrobial peptides (AMPs) seem to be a promising alternative to conventional antibiotics. The aim of this in vitro study was to evaluate the antimicrobial activity of selected AMPs against pathogenic staphylococcal strains, including multidrug- and methicillin-resistant strains isolated from canine pyoderma cases. Seven antimicrobial peptides (aurein 1.2, CAMEL, citropin 1.1, protegrin-1, pexiganan, temporin A and uperin 3.6) synthesized by the 9-fluorenylmethoxycarbonyl (Fmoc) solid-phase method were tested. The minimal inhibitory and minimal bactericidal concentrations (MIC and MBC) were determined by the broth microdilution method. The study showed that analyzed AMPs exerted an extensive effect against canine pathogens, with the most active peptide being uperin 3.6. The tested AMPs were equally efficient against both resistant- and susceptible staphylococcal strains and were more efficient against Staphylococcus pseudintermedius than against Staphylococcus aureus strains. Our findings are particularly interesting from a clinical perspective, as they point to AMPs as potential therapeutic topical agents in canine pyoderma cases associated with antimicrobial resistance of staphylococci.

Hydrogel containing adapalene- and dapsone-loaded lipid-core nanocapsules for cutaneous application: development, characterization, in vitro irritation and permeation studies

Lipid-core polymeric nanocapsule suspensions containing adapalene and dapsone (AD-LCNC) were developed and incorporated in a Carbopol 940® hydrogel (AD-LCNC HG). A nanoemulsion (AD-NE), similarly prepared but omitting the polymer, was developed and also incorporated in a Carbopol 940^® hydrogel (AD-NE HG) to evaluate the polymer effect. Physicochemical characteristics were evaluated. AD-LCNC suspensions containing 0.07% of dapsone and 0.025% of adapalene presented an average size of 194.9 ± 0.42 nm, zeta potential of -15 ± 1.2 mV and polydispersity index of 0.12 ± 0.02, using electrophoretic light scattering (n = 3). The granulometric profiles showed unimodal size distributions for AD-LCNC suspensions, demonstrating that no microscopic population is present in the formulation. No instability phenomena were observed by multiple light-scattering analysis. Photomicrographs obtained by TEM showed homogeneous- and spherical-shaped particles. The encapsulation efficiency was 99.99% for dapsone and 100% for adapalene. The pH values for AD-LCNC suspensions were 5.1 and 7.6 for AD-LCNC HG. Formulations were classified as nonirritant in the HET-CAM test. Rheological analysis demonstrated a non-Newtonian pseudoplastic profile. The in vitro skin permeation studies showed a higher amount of adapalene in epidermis (130.52 ± 25.72 ng/mg) and dermis (4.66 ± 2.5 ng/mg) for AD-NE HG. The AD-LCNC HG presented higher amount of dapsone in both the skin layers (73.91 ± 21.64 ng/mg in epidermis and 4.08 ± 0.85 ng/mg in dermis). The assay showed significant difference between AD-LCNC HG and AD-NE HG (p < 0.05), and drug was not found in the receptor medium.