Tris-EDTA significantly enhances antibiotic efficacy against multidrug-resistant Pseudomonas aeruginosa in vitro

Laura M Buckley, Neil A McEwan, Tim Nuttall

Research output: Contribution to journalArticlepeer-review

Abstract

Multidrug-resistant Pseudomonas aeruginosa commonly complicates chronic bacterial otitis in dogs.
Hypothesis/ObjectivesThe aim of this in vitro study was to determine the effect of ethylenediaminetetraacetic acid-tromethamine (Tris-EDTA) on the minimal bactericidal concentrations (MBCs) and minimal inhibitory concentrations (MICs) of marbofloxacin and gentamicin for multidrug-resistant P.aeruginosa isolates from cases of canine otitis.

MethodsEleven isolates were identified as multidrug resistant on disc diffusion; 10 were resistant to marbofloxacin and two were resistant to gentamicin. Isolates were incubated for 90min with each antibiotic alone and in combination with Tris-EDTA at concentrations of 0.075g/mL to 5mg/mL for marbofloxacin, 0.001g/mL to 10mg/mL for gentamicin and 17.8:4.7 to 0.14:0.04mg/mL for Tris-EDTA. Positive and negative controls were included. Aliquots of each antibiotic and/or Tris-EDTA concentration were subsequently transferred to sheep blood agar to determine the MBCs, and tryptone soy broth was added to the remaining suspensions to determine the MICs.

ResultsTris-EDTA alone was bacteriostatic but not bactericidal at any concentration. The addition of Tris-EDTA significantly reduced the median MBC (from 625 to 468.8g/mL; P

Conclusions and clinical importanceTris-EDTA significantly reduced the MBCs and MICs of marbofloxacin and gentamicin for multidrug-resistant P.aeruginosa in vitro. This may be of use to clinicians managing these infections in dogs.
Original languageEnglish
Pages (from-to)519-e122
JournalVeterinary Dermatology
Volume24
Issue number5
DOIs
Publication statusPublished - Oct 2013

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