Comparative in vitro antimicrobial efficacy of commercial ear cleaners

The aim of this study was to compare the antimicrobial efficacy of ear cleaners against Staphylococcus intermedius, Pseudomonas aeruginosa and Malassezia pachydermatis. Single isolates of each organism were incubated in duplicate at 38 degrees C for 30 min with each ear cleaner diluted 1/2 to 1/256 in phosphate-buffered saline. Positive and negative controls were included. Aliquots were then incubated for 16-18 h on sheep blood agar (bacteria) or for 3 days on Sabouraud's dextrose agar (Malassezia) at 38 degrees C. The lowest dilutions exhibiting 100% antimicrobial efficacy for S. intermedius were: Cleanaural Dog 1/32; Sancerum 1/16; Otoclean 1/4; EpiOtic 1/2; MalAcetic 1/2; and Triz Plus 1/2. The results for P. aeruginosa were Sancerum and Triz Plus 1/16; Cleanaural Dog and EpiOtic 1/8; Otoclean 1/4; and MalAcetic 1/2. Results for M. pachydermatis were: Cleanaural Dog 1/32; Sancerum, Otoclean, EpiOtic and Triz Plus 1/8; and MalAcetic 1/4. Cleanaural Cat, MalAcetic HC and Triz EDTA did not display any antimicrobial activity at any dilution. Antimicrobial activity appeared to be associated with the presence of isopropyl alcohol, parachlorometaxylenol and a low pH. The results of this study may help clinicians make evidence-based decisions when selecting ear cleaners for use in individual cases.