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Tris– EDTA significantly enhances antibiotic efficacy against multidrug‐resistant P seudomonas aeruginosa in vitro
Author(s) -
Buckley Laura M.,
McEwan Neil A.,
Nuttall Tim
Publication year - 2013
Publication title -
veterinary dermatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.744
H-Index - 60
eISSN - 1365-3164
pISSN - 0959-4493
DOI - 10.1111/vde.12071
Subject(s) - gentamicin , minimum bactericidal concentration , minimum inhibitory concentration , tris , microbiology and biotechnology , ethylenediaminetetraacetic acid , agar , chemistry , multiple drug resistance , aminoglycoside , antibiotics , pharmacology , medicine , bacteria , biology , chelation , biochemistry , genetics , organic chemistry
Background Multidrug‐resistant P seudomonas aeruginosa commonly complicates chronic bacterial otitis in dogs. Hypothesis/Objectives The aim of this in vitro study was to determine the effect of ethylenediaminetetraacetic acid–tromethamine (Tris– EDTA ) on the minimal bactericidal concentrations ( MBC s) and minimal inhibitory concentrations ( MIC s) of marbofloxacin and gentamicin for multidrug‐resistant P. aeruginosa isolates from cases of canine otitis. Methods Eleven isolates were identified as multidrug resistant on disc diffusion; 10 were resistant to marbofloxacin and two were resistant to gentamicin. Isolates were incubated for 90 min with each antibiotic alone and in combination with Tris– EDTA at concentrations of 0.075 μg/mL to 5 mg/mL for marbofloxacin, 0.001 μg/mL to 10 mg/mL for gentamicin and 17.8:4.7 to 0.14:0.04 mg/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 MBC s, and tryptone soy broth was added to the remaining suspensions to determine the MIC s. Results Tris– EDTA alone was bacteriostatic but not bactericidal at any concentration. The addition of Tris– EDTA significantly reduced the median MBC (from 625 to 468.8 μg/mL; P < 0.001) and MIC (from 29.3 to 2.4 μg/mL; P = 0.008) of marbofloxacin, and the median MBC (from 625 to 39.1 μg/mL) and MIC (from 19.5 to 1.2 μg/mL) of gentamicin (both P < 0.001). Conclusions and clinical importance Tris– EDTA significantly reduced the MBC s and MIC s of marbofloxacin and gentamicin for multidrug‐resistant P. aeruginosa in vitro . This may be of use to clinicians managing these infections in dogs.