The susceptibility of Pseudomonas spp. isolated from dogs with otitis to topical ear cleaners

Objective To investigate the in vitro efficacy of commercially available topical otic preparations (ear cleaners) against Pseudomonas spp. isolated from canine ear infections. Methods Between January and May 2011, 50 isolates that were morphologically and phenotypically confirmed as Pseudomonas spp. were isolated from 48 dogs that had been identified with clinical signs of otitis externa and media at a referral dermatology clinic in the north west of the UK. The in vitro efficacy of eight different topical preparations against these isolates was investigated using an in-agar inhibition test. Results Of the eight preparations tested, three showed consistently good in vitro activity against Pseudomonas spp., while a further three were consistently ineffective. For the remaining two -preparations, in vitro efficacy was variable and inconsistent. Clinical Significance Topical treatment with ear cleaners is considered to be a valuable adjunct in the treatment of canine otitis that involves multi-antimicrobial-resistant organisms such as Pseudomonas spp. Where treatment with antimicrobials is not an option, the use of these preparations, as a sole form of therapy, may be effective in some cases. As a comparison with other similar studies looking at the activity of ear cleaners against bacterial isolates from otitis, this study uses isolates from 50 ears from 48 dogs providing a significant number of isolates for analysis.