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Merck
  • Antibacterial activity of novel cationic peptides against clinical isolates of multi-drug resistant Staphylococcus pseudintermedius from infected dogs.

Antibacterial activity of novel cationic peptides against clinical isolates of multi-drug resistant Staphylococcus pseudintermedius from infected dogs.

PloS one (2015-01-01)
Mohamed F Mohamed, G Kenitra Hammac, Lynn Guptill, Mohamed N Seleem
초록

Staphylococcus pseudintermedius is a major cause of skin and soft tissue infections in companion animals and has zoonotic potential. Additionally, methicillin-resistant S. pseudintermedius (MRSP) has emerged with resistance to virtually all classes of antimicrobials. Thus, novel treatment options with new modes of action are required. Here, we investigated the antimicrobial activity of six synthetic short peptides against clinical isolates of methicillin-susceptible and MRSP isolated from infected dogs. All six peptides demonstrated potent anti-staphylococcal activity regardless of existing resistance phenotype. The most effective peptides were RRIKA (with modified C terminus to increase amphipathicity and hydrophobicity) and WR-12 (α-helical peptide consisting exclusively of arginine and tryptophan) with minimum inhibitory concentration50 (MIC50) of 1 µM and MIC90 of 2 µM. RR (short anti-inflammatory peptide) and IK8 "D isoform" demonstrated good antimicrobial activity with MIC50 of 4 µM and MIC90 of 8 µM. Penetratin and (KFF)3K (two cell penetrating peptides) were the least effective with MIC50 of 8 µM and MIC90 of 16 µM. Killing kinetics revealed a major advantage of peptides over conventional antibiotics, demonstrating potent bactericidal activity within minutes. Studies with propidium iodide and transmission electron microscopy revealed that peptides damaged the bacterial membrane leading to leakage of cytoplasmic contents and consequently, cell death. A potent synergistic increase in the antibacterial effect of the cell penetrating peptide (KFF)3K was noticed when combined with other peptides and with antibiotics. In addition, all peptides displayed synergistic interactions when combined together. Furthermore, peptides demonstrated good therapeutic indices with minimal toxicity toward mammalian cells. Resistance to peptides did not evolve after 10 passages of S. pseudintermedius at sub-inhibitory concentration. However, the MICs of amikacin and ciprofloxacin increased 32 and 8 fold, respectively; under similar conditions. Taken together, these results support designing of peptide-based therapeutics for combating MRSP infections, particularly for topical application.

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Sigma-Aldrich
6-Mercaptohexanoic acid, 90%
Sigma-Aldrich
Propidium iodide, ≥94% (HPLC)
Sigma-Aldrich
Amikacin hydrate, aminoglycoside antibiotic
Sigma-Aldrich
Propidium iodide, ≥94.0% (HPLC)
Ciprofloxacin, European Pharmacopoeia (EP) Reference Standard
Supelco
Ciprofloxacin, VETRANAL®, analytical standard
Sigma-Aldrich
Ampicillin sodium salt, BioXtra, suitable for cell culture
Sigma-Aldrich
Ciprofloxacin, ≥98% (HPLC)
Sigma-Aldrich
Ampicillin sodium salt
Sigma-Aldrich
Propidium iodide solution
Sigma-Aldrich
Ampicillin sodium salt, powder or crystals, BioReagent, suitable for cell culture
Supelco
Ciprofloxacin, Pharmaceutical Secondary Standard; Certified Reference Material
Supelco
Ampicillin Sodium, Pharmaceutical Secondary Standard; Certified Reference Material
USP
Ampicillin sodium, United States Pharmacopeia (USP) Reference Standard