title: Evaluation of the impact of tromethamine edetate disodium dihydrate on antimicrobial susceptibility of Pseudomonas aeruginosa in biofilm in vitro.
abstract: BACKGROUND
  Biofilm formation by Pseudomonas aeruginosa has been documented in canine otic isolates. An increase in minimal inhibitory concentration (MIC) for specific antibiotics has been noted for biofilm-embedded bacteria. Tromethamine edetate disodium dihydrate buffered to pH 8 with tromethamine hydrochloride and deionized water (Triz-EDTA(®)) has been documented to potentiate bactericidal activity when used in combination with topical antibiotics, but the impact on biofilm-embedded bacteria is unknown.
  
  
  OBJECTIVE
  The objective of this study was to evaluate the impact of Triz-EDTA(®) use on in vitro antimicrobial susceptibility of biofilm-embedded P. aeruginosa.
  
  
  METHODS
  Biofilm formation was documented using a microtitre plate assay. Broth microdilution was used to assess the MIC of neomycin, polymyxin B, enrofloxacin and gentamicin for the biofilm-embedded bacteria. The microtitre plate assay was again used to assess the MIC of neomycin, polymyxin B, enrofloxacin and gentamicin for biofilm-embedded bacteria with added Triz-EDTA(®).
  
  
  RESULTS
  Thirty-one isolates from dogs with otitis were tested. Addition of Triz-EDTA(®) significantly reduced MICs for neomycin (P < 0.003) and gentamicin (P < 0.02) but not for polymyxin B (P = 0.3). Enrofloxacin MICs increased in the presence of Triz-EDTA (P < 0.036).
  
  
  CONCLUSIONS
  Triz-EDTA(®) may be a useful adjunctive treatment for chronic cases of Pseudomonas otitis where biofilms may have developed, if gentamicin or neomycin is to be used as a topical treatment. In vivo study is required to confirm this effect.
authors.affiliation: Yu of Guelph Veterinary Dermatology, Guelph Veterinary Specialty Hospital, 1460 Gordon Street South, Guelph, Ontario, N1L 1C8.
authors.forename: Charlotte C
authors.initials: CC
authors.lastname: Pye
authors.forename: Ameet
authors.initials: A
authors.lastname: Singh
authors.forename: J Scott
authors.initials: JS
authors.lastname: Weese
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D018441:Biofilms / Q000254:growth & development*; D004283:Dog Diseases / Q000382:microbiology; D004285:Dogs; D024881:Drug Resistance, Bacterial; D004492:Edetic Acid / Q000494:pharmacology*; D005079:Excipients / Q000494:pharmacology; D008826:Microbial Sensitivity Tests; D011552:Pseudomonas Infections / Q000382:microbiology / Q000662:veterinary; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000502:physiology; D014325:Tromethamine / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D005079:Excipients; D014325:Tromethamine; D004492:Edetic Acid