title: In vitro antimicrobial activity of a gel containing antimicrobial peptide AMP2041, chlorhexidine digluconate and Tris-EDTA on clinical isolates of Pseudomonas aeruginosa from canine otitis.
abstract: BACKGROUND
  Pseudomonas aeruginosa (PA) may cause suppurative otitis externa with severe inflammation and ulceration in dogs. Multidrug resistance is commonly reported for this organism, creating a difficult therapeutic challenge.
  
  
  OBJECTIVE
  The aim of this study was to evaluate the in vitro antimicrobial activity of a gel containing 0.5 μg/mL of antimicrobial peptide AMP2041, 0.07% chlorhexidine digluconate (CLX), 0.4% Tris and 0.1% EDTA on 30 clinical isolates of PA from canine otitis externa.
  
  
  METHODS
  Antimicrobial activity was evaluated through minimal bactericidal concentration (MBC). Standardized bacterial suspensions were incubated with different concentrations of the gel at 37°C for 30 min and plated for colony forming unit (CFU) counts. Time-to-kill kinetics were evaluated with the undiluted product and at MBC for each PA strain at 30 s, 1, 5, 10, 15, 30 min, 24 and 48 h.
  
  
  RESULTS
  The MBC was 1:64 for two of 30 strains, 1:128 for 15 of 30 strains and 1:256 for 13 of 30 strains. The geometric mean was 1:165, equivalent to a concentration of 0.003 μg/mL AMP2041 + 0.0004% CLX + 0.0024%Tris + 0.0006% EDTA. Time-to-kill assays with the undiluted product showed complete bactericidal effect within 30 s for all isolates, whereas at the MBC this effect was reached within 5 min for 20 of 30 isolates and within 30 min for all isolates. Bactericidal activity was maintained after 48 h for all isolates.
  
  
  CONCLUSIONS
  This gel has shown rapid, complete and long-lasting activity against a panel of 30 PA isolates from cases of canine otitis externa.
authors.affiliation: Clinica Veterinaria Malpensa, via G. Marconi 27, 21017, Samarate (VA), Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Ghibaudo
authors.affiliation: Dipartimento di Scienze Medico-Veterinarie, University of Parma, via del Taglio 10, 43126, Parma, Italy.
authors.forename: Davide
authors.initials: D
authors.lastname: Santospirito
authors.affiliation: Dipartimento di Scienze Medico-Veterinarie, University of Parma, via del Taglio 10, 43126, Parma, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Sala
authors.affiliation: Dipartimento di Scienze Medico-Veterinarie, University of Parma, via del Taglio 10, 43126, Parma, Italy.
authors.forename: Sara
authors.initials: S
authors.lastname: Flisi
authors.affiliation: Dipartimento di Scienze Medico-Veterinarie, University of Parma, via del Taglio 10, 43126, Parma, Italy.
authors.forename: Simone
authors.initials: S
authors.lastname: Taddei
authors.affiliation: Dipartimento di Scienze Medico-Veterinarie, University of Parma, via del Taglio 10, 43126, Parma, Italy.
authors.forename: Sandro
authors.initials: S
authors.lastname: Cavirani
authors.affiliation: Dipartimento di Scienze Medico-Veterinarie, University of Parma, via del Taglio 10, 43126, Parma, Italy. clotildesilvia.cabassi@unipr.it.
authors.forename: Clotilde Silvia
authors.initials: CS
authors.lastname: Cabassi
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000627:therapeutic use*; D023181:Antimicrobial Cationic Peptides / Q000627:therapeutic use*; D002710:Chlorhexidine / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000627:therapeutic use; D004283:Dog Diseases / Q000382:microbiology*; D004285:Dogs; D004492:Edetic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology*; D005782:Gels; D010032:Otitis Externa / Q000382:microbiology / Q000662:veterinary*; D011550:Pseudomonas aeruginosa / Q000187:drug effects*; D014325:Tromethamine / Q000031:analogs & derivatives* / Q000494:pharmacology*
chemical_list: C000618832:AMP2041; D000900:Anti-Bacterial Agents; D023181:Antimicrobial Cationic Peptides; D005782:Gels; D014325:Tromethamine; D004492:Edetic Acid; C010882:chlorhexidine gluconate; D002710:Chlorhexidine