An Ear Cleaner Comparison

Otitis externa is a problem in small animal practice. The causes of the condition are multifactorial, and it can be a complicating problem in many diseases. Treatment involves ear cleaning, and for some underlying skin diseases, ear cleaning is the mainstay of preventing recurrence of disease. This study compared the antimicrobial efficacy of 9 commercial ear cleaners against Staphylococcus intermedius, Pseudomonas aeruginosa, and Malassezia species. One strain of each pathogen was incubated for 30 minutes with each ear cleaner diluted 1:2-1:256. Bacterial aliquots were incubated on blood agar plates for 16 to 18 hours and on Sabouraud's dextrose agar for Malassezia for 3 days. The commercial products tested were Sancerum (intervet.com), EpiOtic Advanced Formula (virbac.com), Cleanaural Dog (dechra.com), Cleanaural Cat (dechra.com), Otoclean (janssenanimalhealth.com), Malacetic Otic (dermapet.com), Malacetic HC (dermapet.com), Triz Plus (dermapet.com), and TrizEDTA (dermapet.com). For S intermedius, the lowest dilutions resulting in 100% antimicrobial activity were the following: Cleanaural Dog, 1:32; Sancerum, 1:16; Otoclean, 1:4; EpiOtic, 1:2; MalAcetic and Triz Plus, 1:2. For Pseudomonas, the lowest dilutions were the following: Sancerum and Triz Plus, 1:16; Cleanaural Dog and EpiOtic, 1:8; Otoclean, 1:4; and MalAcetic, 1:2. For Malassezia, the lowest dilutions were the following: Cleanaural Dog, 1:32; Sancerum, Otoclean, EpiOtic, and TrizPlus, 1:8; and MalAcetic, 1:4. Three products did not show any antimicrobial activity at any dilution: Cleanaural Cat, Malacetic HC, and Triz EDTA. Key active ingredients/factors associated with good antimicrobial activity were isopropyl alcohol, parachlorometaxylenol, and a low pH.

COMMENTARY: After a lecture on ear disease or during a consultation on ear disease, someone always asks, "Which ear cleaner should I use?" There are properties of ear cleaners, such as antimicrobial, ceruminolytic, or antiinflammatory properties, that are important when selecting a particular ear cleaner. Previous articles have compared the in vivo antimicrobial properties of ear cleaners, but none determined the minimum inhibitory concentration (MIC) of the cleaners. The MIC is defined as the lowest concentration of antimicrobial that will inhibit the visible growth of a microorganism after incubation. This article compares 9 ear cleaners, 5 available in the United States, and characterizes one important property of ear cleaners: their MIC. The results can be used clinically in the same way you would use a standard bacterial culture with MIC. The authors acknowledge that one disadvantage of this in vitro study is that it may not replicate antimicrobial efficacy in vivo. To be even more meaningful, this study should be performed in clinical cases. For now, however, this is a very good starting point.

Comparative in vitro antimicrobial efficacy of commercial ear cleaners. Swinney A, Fazakerley J, McEwan N, Nuttall T. VET DERMATOL 19:373-379, 2008.