New combination for the therapy of canine otitis externa. I. Microbiology of otitis externa.

In order to compound a new drug combination against canine otitis externa (OE), 515 dogs affected with OE were subjected to physical examination and microbiological analysis of their ear exudates. OE was erythematous-ceruminous in 83 per cent and suppurative in 17 per cent of the patient material. Erythematous-ceruminous inflammations were characterised by severe pruritus and accumulation of brownish, greasy cerumen in the auditory canal. The yeast Malassezia pachydermatis was isolated from the ears of 76 per cent of the dogs, often in combination with Staphylococcus intermedius bacteria. M pachydermatis showed the most sensitivity, in decreasing order of efficacy, to ketoconazole, econazole, clotrimazole, miconazole and nystatin. S intermedius isolates were most sensitive to amoxycillin-clavulanic acid, enrofloxacin, cephalexin and gentamicin. The microorganism most frequently isolated from dogs with suppurative OE was Pseudomonas aeruginosa; in some cases Proteus, Streptococcus and Pasteurella were also isolated. The P aeruginosa isolates showed the highest sensitivity to gentamicin, polymyxin B and tobramycin.