Efficacy of a pimaricin suspension for treating otitis externa associated with M pachydermatis

A clinical trial was conducted to evaluate the efficacy of a 1 per cent pimaricin suspension in the treatment of canine otitis externa associated with Malassezia pachydermatis. Of 40 dogs examined, M pachydermatis was the sole infection in five ears and was commensal with other organisms in 35 ears. Pimaricin in a 1 per cent suspension was administered twice a day for two weeks. Employing continuous therapy, signs accompanying otitis externa were ameliorated steadily, and satisfactory results were achieved in 33 of the dogs. No noticeable side effects were observed with the pimaricin suspension.     

A clinical trial of a topical preparation of miconazole, polymyxin and prednisolone in the treatment of otitis externa in dogs

A topical preparation containing miconazole, polymyxin and prednisolone was shown to be more effective in the treatment of otitis externa in 167 dogs than 2 other ear preparations containing antibiotics, an antimycotic and a corticosteroid. With miconazole, polymyxin and prednisolone, the recurrence rate was 26.7% compared with 72.6% and 54.3% when the other products were used. The mean duration of treatment required to achieve resolution of clinical signs was 9.6 days, compared with 12.2 days and 13.0 days and no cases failed to respond to treatment, compared with 17.7% and 14.3%. Malassezia canis alone (71%) or in association with bacteria (18%) was recovered from 44 of 49 ears cultured.     

Study of lipid in the ear canal in canine otitis externa with Malassezia pachydermatis

An epidemiological investigation of 120 canine otitis externa cases in 1,370 dogs was done on the incidence rate, ear pinna shapes, breeds and their relationships. Eighty-five cases (12.6%) in 672 dogs with pendulous ears and 35 cases (5.0%) in 698 dogs with erect ears had otitis externa, and the difference between them was significant (P<0.05). Ninety-five auditory cerumen specimens were cultured for Malassezia pachydermatis (M. pachydermatis) and analyzed for concentrations of major fatty acids. Although rates of cases positive for M. pachydermatis in both ear pinna shapes were almost the same, i.e. 55.2% in the pendulous group and 53.6% in the erect group, the average total fatty acid level of the pendulous ear group was significantly (P<0.05) higher than that in the erect ear group after dismissing extraordinary levels in the Siberian husky. Isolated M. pachydermatis strains were examined for the effects of fatty acid supplementation on their growth. The majority of the strains utilized fatty acids and grew faster in fatty acid supplemented broth. These results suggest that M. pachydermatis, the predominant causative agent of canine otitis externa, prefers the auditory canal of dogs with lipid-rich earwax and grows fast, but growth strongly depends upon the canine breed.     

Otitis externa induced with Malassezia pachydermatis in dogs and the efficacy of pimaricin.

Eight beagles were experimentally inoculated intraotally with Malassezia pachydermatis to induce acute otitis externa. Three or 4 days after the inoculation, the animals showed the symptoms of otitis externa. All ear canals were erythematous and the dogs were shaking their heads. A large number of M. pachydermatis was noticed in exudate taken from every ear canal. Clinical signs of otitis externa were reduced after treatment with 0.1 ml (per canal) of 1% pimaricin suspension twice a day for 3 days. The amount of exudate decreased gradually and 12 of the 16 ear swabs examined, thereafter, were found to be negative for M. pachydermatis within 10 days. No side effects were observed in all the treated cases. These results suggested that M. pachydermatis could induce the canine otitis externa, and that pimaricin is effective agent for M. pachydermatis infection in ear canals.     

Attachment of Malassezia pachydermatis to the ear dermal cells in canine otitis externa.

To investigate the predominance of Malassezia pachydermatis (M. pachydermatis) as a causative agent of canine otitis externa, ear cerumen samples were observed for adhesion of M. pachydermatis to the cornified epithelial cells by light and electron microscopes. The yeasts appeared not to adhere to the cornified epithelial cells directly, but they seemed to exist in the proximity of the epithelial cells with an electron opaque halo-like space around them. Polysaccharide and lipid staining techniques were conducted to identify the substances existing in that space. Lipid substances, not saccharides, were observed around the yeasts and the cornified epithelial cells. These results suggested that in the canine ear canal malassezia yeast attachment to the cornified epithelial cells is mediated by lipids.     

Effects of beta-thujaplicin on anti-Malassezia pachydermatis remedy for canine otitis externa

The antifungal activity of beta-thujaplicin was evaluated against 51 Malassezia pachydermatis strains isolated from canine ear canals with or without otitis externa. For comparison, sensitivity tests were performed on M. pachydermatis isolates for nystatin, ketoconazole, and terbinafine HCl, all clinically available antifungal agents. The minimal inhibition concentrations over 50% of the tested isolates (MIC50) were 3.13 microg/ml for beta-thujaplicin and nystatin, 0.016 microg/ml for ketoconazole, and 1.56 microg/ml for terbinafine HCl. The antifungal effect for M. pachydermatis of beta-thujaplicin compared favorably with commercial antifungal agents. None of the 51 M. pachydermatis isolates showed resistance against any of the tested antibiotics investigated in this study. Ten representative isolates of M. pachydermatis were subcultured for 30 generations at concentrations close to the MIC levels of beta-thujaplicin, nystatin, ketoconazole, and terbinafine HCl, and examined to determine whether they had acquired resistance to each drug. As a result, M. pachydermatis was found to achieve resistance more easily for ketoconazole and terbinafine HCl than for beta-thujaplicin or nystatin. The MIC50 of beta-thujaplicin did not change during the course of subculture, and it is thought that the potential development of a resistant strain is low, even with continuous infusion for otitis externa therapy. beta-Thujaplicin is an inexpensive and safe treatment with anti-inflammatory and deodorant effects that can be recommended as an effective remedy for canine otitis externa.     

The association of Pityrosporum pachydermatis with the normal external ear canal of dogs and cats

The frequency of Pityrosporum pachydermatis within the non-otitic external ear canals of dogs and cats has been investigated and an assessment of the abundance of the yeast made by microscopic and cultural techniques. It was present in varying amounts in 49% of clean dog ears and 23% of clean cat ears. Microscopically, 14% of the ears were found to contain the yeast in large numbers. A further 3 % of ears examined showed excessive cerumen production and all these contained the yeast.
The prevalence of P. pachydermatis in non-otitic ears of both dogs and cats was similar to that previously reported in otitic ears.     

Diagnosis and medical treatment of otitis externa in dogs and cats

A review of otitis externa in dogs and cats is presented. Aetiology, includes primary causes: ectoparasitoses, allergic diseases, endocrine disorders, pyodermas, trauma and irritation, contact dermatitis, auto-immune skin diseases, drug eruption, keratoseborrhoeic skin disease, tumours and pseudoneoplastic lesions, as well as secondary causes: bacteria and yeasts. Clinical aspects are variable but a practical classification distinguishes two forms: erythematoceruminous otitis externa and suppurative otitis externa. Diagnosis is made in five steps which are clinical examination, direct examination of cerumen (erythematoceruminous otitis externa) or bacterial culture and sensitivity testing (suppurative otitis externa), direct impression smears, cleaning and otoscopy, and diagnosis of underlying skin disease. Medical therapy includes cleaning of the external ear canal and local therapy (acaricides, antifungal agents, antibiotics, corticosteroids, other topical agents, the appropriate selection of an optic preparation being essential). Treatment of underlying skin disease is always necessary. Otitis externa is in fact a dermatological disease complex (like pododermatitis). Although local secondary infections (bacterial and fungal) must be managed in every case, there are grounds for including otitis externa in a larger frame.     

Evaluation of a cuprimyxin-hydrocortisone acetate suspension in the treatment of otitis externa in dogs and cats.

The therapeutic efficacy of a 0.5% cuprimyxin plus 1% hydrocortisone acetate-water-base suspension was evaluated in 130 clinical cases of otitis externa in dogs and cats in various geographic areas of the United States. The otic microbial flora was studied before treatment in 125 (96%) of the dogs and cats, with multiple isolates recovered from mated from 70%, yeasts from 65%, and fungi from 5% of the animals. Evens though multiple drug reistance was frequently observed in the bacterial flora, all bacteria and yeast isolates were sensitive to cuprimyxin. Of the 130 treated animals, a statistically significant (P less than 0.01) favorable response was obtained in 84,6% and no response in 13;1%; in2.3%, the condition became worse. An adverse reaction (pain at the time of first application) was observed in 1 (0.8%) animal.     

Bacteriology and mycology of otitis externa in dogs]

The bacterial and fungal flora of 1118 ears of dogs with otitis externa and 100 ears of healthy control dogs were studied in order to isolate the causative agents. The yeast Malassezia pachydermatis (56%) was by far the most common organism in otitic dogs followed by the bacteria Staphylococcus intermedius (23%), Pseudomonas aeruginosa (12%), Proteus spp. (6%) and Streptococcus canis (5%). A statistical analysis of observed results showed that the incidence of these organisms is significant in otitic dogs. Many strains of S.intermedius, P.aeruginosa and Proteus spp. are resistant to antimicrobial agents commonly used to treat otitis externa. Therefore an antimicrobial susceptibility testing was performed using "Cobas Bact" for these bacterias. Furthermore, 80 strains of M.pachydermatis were submitted to identification-kits (API 20 CAUX, API STAPH, Cobas Micro). The observed results showed that an identification with these tests was not possible.     

Antimicrobial susceptibility of Pseudomonas aeruginosa isolates from dogs with otitis externa

Pseudomonas aeruginosa is a common cause of otitis externa in dogs, and treatment of these infections is becoming problematic because of the increasing number of multiresistant strains. The aim of the present study was to compare the in vitro activities of cefepime, ceftazidime, enrofloxacin, ciprofloxacin, gentamicin and ticarcillin/clavulanic acid against 104 strains of P aeruginosa isolated from dogs with otitis externa. Antimicrobial susceptibility and minimum inhibitory concentrations, in μg/ml, were evaluated by the E test (bioMérieux). The most active compound was ceftazidime, with 100 per cent efficiency. The majority of tested strains were susceptible to ticarcillin/clavulanic acid (89.4 per cent), followed by ciprofloxacin (88.5 per cent) and cefepime (60.6 per cent). The highest resistance was observed to enrofloxacin (51.9 per cent) and gentamicin (43.3 per cent). Large numbers of strains were intermediately susceptible to antibiotics registered for use in veterinary medicine in Croatia--enrofloxacin (47.1 per cent) and gentamicin (41.3 per cent).     

Evaluation of an ear cleanser for the treatment of infectious otitis externa in dogs

Thirty-one ears (16 dogs) with otitis externa originating from bacterial or yeast infections were enrolled in a study to evaluate the in vivo efficacy of an ear cleanser containing 2.5% lactic acid and 0.1% salicylic acid for the treatment of infectious otitis externa. The affected ears were treated with the ear cleanser twice daily for 2 weeks and evaluated after 1 and 2 weeks of treatment. The ear cleanser was effective in resolution of infection in 67.7% of the ears, and clinical signs of infectious otitis externa were significantly reduced within 2 weeks.     

The bacteriological and clinical assessment of a new preparation for the treatment of otitis externa in dogs and cats

The efficacy of a preparation (Oterna—Glaxo Laboratories Ltd) for use in the treatment of otitis externa in small animals has been assessed bacteriologically. The aetiology of the disease was studied in 133 ears of cats and dogs; normal ears were examined by comparison. Pityrosporum canis and staphylococci were the organisms most commonly isolated; their incidence was much higher in clinically affected ears than in normal ears. Gram-negative organisms were found only in diseased ears. Seventy-three clinical cases of otitis in dogs and cats were treated with a preparation containing neomycin, monosulfiram and betamethasone. Bacteriological and clinical evaluations were made before and after treatment and the organisms isolated were tested for sensitivity to the antimicrobial constituents of the preparation. There was a 92 % correlation between the bacteriological and clinical results. A ‘good’ or ‘very good’ bacteriological response was recorded for 71% of the ears treated. Résumé. On a évalué bactériologiquement l'efficacité d'une préparation (Oterna—Glaxo Laboratories Ltd) pour l'usage dans le traitement de l'otite externe de petits animaux. L'étiologie de la maladie a été étudiée dans 133 oreilles de chats et chiens; des oreilles normales ont été examinées pour comparaison. Le Pityrosporum canis et des staphylocoques ont été les microorganismes le plus souvent isolés; leur incidence était beaucoup plus élevée dans les oreilles affectées cliniquement que dans les oreilles normales. Des micro-organisms Gram-négatifs ont été seulement trouvés dans les oreilles malades. Soixante-treize cas cliniques d'otite chez les chats et les chiens ont été traités avec une préparation contenant de la néomycine, du monosulfiram et du bétaméthazone. Les évaluations bactériologique et clinique ont été faites avant et après le traitement et les micro-organismes isolés ont été vérifiés pour la sensibilité aux constituants antimicrobiens de la préparation. Il y avait une corrélation de 92% entre les résultats bactériologiques et cliniques. On a enregistré une réaction bactériologique ‘bonne’ ou ‘très bonne’ dans 71% des oreilles traitées. Zusammenfassung. Die Wirksamkeit eines Präparats (Oterna—Glaxo Laboratories Ltd) für die Behandlung von äußerer Otitis bei kleinen Tieren ist bakteriologisch bestimmt worden. Die Ursachenforschung dieser Krankheit wurde an 133 Ohren von Katzen und Hunden durch-geführt. Zum Vergleich wurden normale Ohren untersucht. Pityrosporum canis und Staphylokokken waren die am häufigsten abgesonderten Lebewesen. Ihr Vorkommen war bei klinisch betroffenen Ohren viel größer als bei normalen Ohren. Gram-negative Lebewesen wurden nur in kranken Ohren vorgefunden. Dreiundsiebenzig klinische Fälle von Otitis bei Hunden und Katzen wurden mit einem Präparat behandelt, das Neomycin, Monosulfiram und Betamethasone enthielt. Bakteriologische und klinische Bewertungen wurden vor und nach Behandlung durchgeführt, und die abgesonderten Lebewesen wurden auf Empfindlichkeit gegen mikrobenbetreffende Bestandteile des Präparates geprüft. Zwischen den bakteriologischen und klinischen Ergebnissen bestand eine 92 prozentige Wechselbeziehung. Eine “gute” oder “sehr gute” bakteriologische Reaktion wurde an 71% der behandelten Ohren festgestellt.     

Isolation of Malassezia pachydermatis and M. sympodialis from the external ear canal of cats with and without otitis externa

The objective of this study was to determine the presence of Malassezia spp. in the external ear canal of cats with and without otitis. Forty-five animals were studied, 20 with and 25 without otitis externa (OE). Cerumen or secretion from external ear canal samples was cultured on modified Mycosel agar and sterile olive oil was added to the surface of the medium before specimen seeding. The isolates were analysed for macro- and micromorphology and identified by catalase tests and on the basis of growth on Tween 20, 40, 60 and 80. Malassezia spp. were isolated from 15 out of 20 (75%) animals with otitis and from 7 out of 25 (28%) cats without OE; the difference between the two groups was statistically significant (P < or = 0.05). Malassezia pachydermatis and M. sympodialis were isolated from 60% (12/20) and 40% (8/20) of cats with otitis, respectively, with no significant difference in the frequency of isolation between the two species. In the microflora of the healthy ear canal M. pachydermatis was significantly more common (6/25, 24%) than M sympodialis (1/25, 4%). The present investigation confirms that M. sympodialis can also act as an aetiological agent of feline OE, and if commercial veterinary laboratories do not use media with added lipids for the isolation of Malassezia spp., this might lead to false-negative results.     

Causes of otitis externa.

Dogs with long-standing, chronic, recurrent otitis externa often represent one of the most frustrating types of problems in daily clinical practice. The important aspect of this discussion is that the clinician may be presented with a patient in which the primary chief complaint is otitis externa but a wide variety of disease processes may be causing the problem, including various combinations of the primary, predisposing, and perpetuating causes as discussed previously. The use of a thorough history and general and dermatologic physical examinations often leads the clinician to establish a systematic approach to identify the specific underlying problems. Until this is accomplished, the recurrent nature of the otitis externa will remain as a persistent problem.