title: Evaluation of biofilm production by Pseudomonas aeruginosa from canine ears and the impact of biofilm on antimicrobial susceptibility in vitro.
abstract: BACKGROUND
  Pseudomonas aeruginosa is a common cause of canine otitis; P. aeruginosa biofilm formation has been documented in human medicine, but the role of biofilms in canine disease is not well documented. Bacteria within biofilms can be more resistant to antibiotics compared with their planktonic form; therefore, understanding the biofilm-forming capacity of isolates and their susceptibility to antimicrobials is important when developing treatment regimens.
  
  
  OBJECTIVE
  To evaluate the biofilm-forming capacity of canine otic isolates of P. aeruginosa and to compare the minimal inhibitory concentration (MIC) of the planktonic versus biofilm-embedded bacteria.
  
  
  METHODS
  Biofilm-forming ability was assessed using a microtitre plate assay. Broth microdilution was used to assess the MICs of neomycin, polymyxin B, enrofloxacin and gentamicin for the planktonic and biofilm-embedded bacteria.
  
  
  RESULTS
  Eighty-three isolates from dogs with otitis were tested; 33 (40%) were classified as biofilm producers. Biofilm MICs for polymyxin B, neomycin, gentamicin and enrofloxacin were significantly higher than for the planktonic form (P < 0.05).
  
  
  CONCLUSIONS
  Biofilm production by otitis isolates of P. aeruginosa is common and may play a role in the pathogenesis of disease. The MICs for biofilm-embedded bacteria differ from their planktonic counterparts, potentially leading to a lack of response to treatment. If polymyxin B, gentamicin, neomycin or enrofloxacin is to be used for topical treatment of a Pseudomonas otitis, the concentration of the medication should be increased, in particular if addressing chronic otitis, because biofilms may have developed.
authors.affiliation: Department of Clinical Studies, Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada. cpdermvet@hotmail.com
authors.forename: Charlotte C
authors.initials: CC
authors.lastname: Pye
authors.forename: Anthony A
authors.initials: AA
authors.lastname: Yu
authors.forename: J Scott
authors.initials: JS
authors.lastname: Weese
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D018441:Biofilms / Q000187:drug effects / Q000254:growth & development*; D004283:Dog Diseases / Q000188:drug therapy / Q000382:microbiology*; D004285:Dogs; D024881:Drug Resistance, Bacterial; D008826:Microbial Sensitivity Tests; D010031:Otitis / Q000382:microbiology / Q000662:veterinary; D011552:Pseudomonas Infections / Q000382:microbiology / Q000662:veterinary*; D011550:Pseudomonas aeruginosa / Q000502:physiology*
chemical_list: D000900:Anti-Bacterial Agents