title: In vitro antimicrobial activity of miconazole and polymyxin B against canine meticillin-resistant Staphylococcus aureus and meticillin-resistant Staphylococcus pseudintermedius isolates.
abstract: BACKGROUND
  Meticillin-resistant Staphylococcus aureus (MRSA) and meticillin-resistant Staphylococcus pseudintermedius (MRSP) infections are increasingly reported in dogs, and these bacteria may be isolated from ear infections.
  
  
  OBJECTIVE
  The main aim of the present study was to investigate the in vitro antimicrobial activity of miconazole, polymyxin B and a combination of both against 24 canine MRSA and 50 canine MRSP isolates. The minimal inhibitory concentration (MIC) values of 12 other antimicrobial agents were also determined.
  
  
  METHODS
  All MIC values were determined according to a broth microdilution assay.
  
  
  RESULTS
  Acquired resistance was found to all tested agents, except for linezolid, miconazole and polymyxin B. The MIC values for miconazole and polymyxin B against MRSA were in the range of 4-8 and 8-64 μg/mL, respectively, while the MIC values for miconazole and polymyxin B against MRSP were in the range of 1-2 and 0.25-4 μg/mL, respectively. Using a combination of miconazole and polymyxin B, there was no evidence for enhanced in vitro activity of the combination (i.e. synergy) of both products. Nevertheless, MIC(90) values of the combination of these antimicrobial agents and of a commercial product containing both agents were at least 1000 times lower than the concentration present in the commercial product.
  
  
  CONCLUSIONS
  These results indicate that the topical use of a combination of miconazole and polymyxin B in a 43.5:1 ratio may have potential for the treatment of MRSA-mediated and MRSP-associated otitis externa in dogs.
authors.affiliation: Department of Pathology, Bacteriology and Avian Diseases, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820 Merelbeke, Belgium. filip.boyen@ugent.be
authors.forename: Filip
authors.initials: F
authors.lastname: Boyen
authors.forename: Koen M H W
authors.initials: KM
authors.lastname: Verstappen
authors.forename: Manuelle
authors.initials: M
authors.lastname: De Bock
authors.forename: Birgitta
authors.initials: B
authors.lastname: Duim
authors.forename: J Scott
authors.initials: JS
authors.lastname: Weese
authors.forename: Stefan
authors.initials: S
authors.lastname: Schwarz
authors.forename: Freddy
authors.initials: F
authors.lastname: Haesebrouck
authors.forename: Jaap A
authors.initials: JA
authors.lastname: Wagenaar
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D004283:Dog Diseases / Q000382:microbiology; D004285:Dogs; D016106:Methicillin Resistance; D008825:Miconazole / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D011112:Polymyxin B / Q000494:pharmacology*; D013207:Staphylococcal Skin Infections / Q000382:microbiology / Q000662:veterinary; D013210:Staphylococcus / Q000145:classification* / Q000187:drug effects*
chemical_list: D000900:Anti-Bacterial Agents; D008825:Miconazole; D011112:Polymyxin B