Treating Canine Otitis Externa With An EDTA-TRIS-SDS Combination

Vet Med 83[10] : 1088-1091 Oct'88 24 Refs
1Richard E. Wooley, DVM, Ph.D.; Harry W. Dickerson, BVSc, PhD; William R. Engen, DVM
1Dept of Med Microbiology, College of Vet Med, Univ of Georgia, Athens, GA 30602

Experimental study reports on the in vitro activity of a combination of 5.0 mM ethylenediaminetetraacetate [EDTA], 50.0 mM tris[hydroxymethyl]aminomethane [TRIS], and 0.05% sodium dodecyl sulfate [SDS], with a pH = 8.0, against Bacillus spp, Staphylococcus aureus, Candida spp, Pseudomonas aeruginosa, E. coli, Proteus vulgaris, Trichosporon spp., and an alpha Streptococcus. The procedure for evaluating synergy between EDTA-TRIS and SDS is described.

In vivo evaluation of the combination in clinical cases of otitis externa in 24 dogs is reported. Fifteen cases were acute; nine were chronic. All were evaluated with bacterial culture before and after treatment.

TREATMENT consisted of applying lavage solution to the ears TID until resolution or for 3 weeks if no clinical response occurred. Method of application/treatment is not described. The study was a clinical trial, not a controlled study. Dogs were examined for irritation of the ears after treatment.

RESULTS from the in vitro studies showed that the EDTA-TRIS- SDS had synergistic activity against Bacillus spp, P. aeruginosa, E. coli, and P. vulgaris. Additive activity was found against S. aureus, Candida spp and Trichosporon spp.

In the clinical trials, 23 of 24 cases were resolved; no adverse effects were seen; duration of follow-up is not specified. The one case that failed to respond was a chronic mixed infection of E. coli and Proteus spp, inflammation was reduced, but the infection persisted. Most cases responded within 1 week, but P. aeruginosa infections required 1 - 3 weeks of treatment.