Serum antibodies to Malassezia yeasts in canine atopic dermatitis

Significant numbers of humans with atopic dermatitis develop Malassezia-specific IgE. Immediate skin-test reactivity to Malassezia has been demonstrated in atopic dogs. The aim of this study was to compare the serum IgG and IgE response to Malassezia in atopic dogs with and without clinical evidence of Malassezia dermatitis and/or otitis, nonatopic dogs with clinical evidence of Malassezia dermatitis and/or otitis and healthy dogs. Cytology was used to diagnose clinically significant Malassezia dermatitis and otitis. Contact plate cultures confirmed the validity of this technique. Reproducible enzyme-linked immunosorbent assays for Malassezia-specific IgG and IgE in canine serum were established. Atopic dogs had significantly higher serum IgG and IgE levels than either healthy dogs or nonatopic dogs with clinical evidence of Malassezia dermatitis and/or otitis. There was no significant difference in IgG and IgE levels between atopic dogs with and without clinical evidence of Malassezia dermatitis and/or otitis. The implications of these findings in the pathogenesis and management of canine atopic dermatitis are discussed.     

北京地区犬马拉色菌耳炎的流行病学调查

马拉色菌耳炎是犬常见的一种疾病,试验对北京地区犬马拉色菌耳炎流行病学进行调查。临床病例分析结果表明,马拉色菌耳炎12个月均有发病,但有一定的季节性,其中6、7月份为发病高峰;患犬性别差异不大;不同品种对马拉色菌易感性不一样,可卡犬和北京杂品种犬发病率最高,其次是松狮犬;发病年龄主要集中在5岁以下;发生马拉色菌感染时,通常还发生其它部位的感染,统计结果发现,背部是最易发生感染的地方,其次是面部和胸部。     

A unique isolate of Malassezia from a cat

An isolate of Malassezia from a cat with otitis externa was examined mycologically as well as molecularly. The isolate was similar to M. sympodialis in morphological and biochemical characteristics. In molecular analysis, however, it differed from the 7 species of Malassezia previously reported. Therefore, this clinical isolate from a cat might be a new species of Malassezia.     

Frequency of yeasts and dermatophytes from healthy and diseased dogs.

The aim of this study was to investigate the presence of dermatophytes and yeasts in healthy and diseased dogs. A total of 633 samples were collected from 26 healthy animals (104 samples), 131 with dermatitis (343 samples), 74 with otitis (148 samples), and 19 with ocular diseases (38 samples). Cultures from healthy animals were positive for Malassezia pachydermatis in 13.5% (7/52) of samples from skin, 42.3% (11/26) from ear, and 3.8% (1/26) from eye. Fungal growth was observed in 20.4% (70/343) samples from animals with dermatitis. Microsporum canis was the most isolated fungus (n = 39), followed by M. pachydermatis (n = 30) and Malassezia sp. (n = 3). Of the 148 samples from dogs with otitis, 90 (60.8%) were positive for M. pachydermatis, and of the clinical specimens from the conjunctiva of animals with ophthalmic disease, 2.6% (1/38) presented positive cultures for M. pachydermatis. Only 14.3% (2/14) of the positive cultures for M. pachydermatis and 40.9% (9/22) of those for M. canis were positive in the direct exam. Direct exams were positive in 84.3% (70/83) of the culture positive samples from affected ears of dogs with otitis. Malassezia pachydermatis may act as an aggravating factor in the occurrence of cutaneous diseases, or the isolation of M. canis may be associated with the onset of dermatophytosis. Fungal culture, rather than microscopic examination, should be used as the definitive diagnostic test for dermatomycoses and otitis.     

In vitro activity of an ear rinse containing tromethamine, EDTA, benzyl alcohol and 0.1% ketoconazole on Malassezia organisms from dogs with otitis externa

The purpose of this study was to evaluate the in vitro activity of an ear rinse containing tromethamine, EDTA, benzyl alcohol and 0.1% ketoconazole in purified water on Malassezia organisms from dogs with otitis externa. Malassezia organisms were collected from ear swab samples from the external ear canal of 19 dogs with otitis externa plus one control strain of Malassezia pachydermatis. Three test solutions were evaluated: ER (EDTA, tromethamine, benzyl alcohol), ER + keto (EDTA, tromethamine, benzyl alcohol, ketoconazole), and H2O (purified water). Ten-millilitre aliquots of each test solution was transferred into 20 tubes and inoculated with one of the isolates (1 tube per isolate: 19 clinical and 1 control strain). Samples were retrieved from each tube at five time points (0, 15, 30, 45 and 60 min), transferred to Petri dishes, mixed with Sabouraud dextrose agar supplemented with 0.5% Tween 80 and incubated. Following incubation, the plates were examined for growth and colonies counted as colony-forming units per millilitre. The data were analysed using a repeated measures analysis, with pair-wise comparisons of solution-time combinations. There was a significant reduction in Malassezia growth in ER + keto at all time points (P < 0.0001) compared to time zero. Neither ER nor H2O had any effect on the growth of Malassezia. ER + keto was significantly more effective in reducing Malassezia growth (P < 0.0001) at all time points compared to both ER and H2O. ER + keto may be useful in the treatment of Malassezia otitis externa. Future studies should be performed to evaluate the in vivo efficacy of ER + keto as treatment for otic infections caused by Malassezia.     

Mycologic disorders of the skin

Cutaneous tissue can become infected when fungal organisms contaminate or colonize the epidermal surface or hair follicles. The skin can be a portal of entry for fungal infection when the epithelial barrier is breached or it can be a site for disseminated, systemic fungal disease. The two most common cutaneous fungal infections in small animals are dermatophytosis and Malassezia dermatitis. Dermatophytosis is a superficial cutaneous infection with one or more of the fungal species in the keratinophilic genera Microsporum, Trichophyton, or Epidermophyton. Malassezia pachydermatis is a nonlipid dependent fungal species that is a normal commensal inhabitant of the skin and external ear canal in dogs and cats. Malassezia pachydermatis is the most common cause of Malassezia dermatitis. The diagnosis and treatment of these cutaneous fungal infections will be discussed.     

Malassezia pachydermatis isolated from normal and diseased external ear canals in dogs: a comparative analysis

To investigate the role of Malassezia pachydermatis as a pathogenic agent in canine otitis, a comparative analysis of isolates from normal and diseased external ear canals in dogs was undertaken. Specimens were collected from the ears of dogs with unilateral or bilateral otitis and from healthy dogs. Mycological analysis was by direct microscopy and fungal culture on Sabouraud's dextrose agar and Dixon's agar. Of the otitis specimens, 63.7% showed typical Malassezia cells on cytological examination. In samples taken from the healthy ears of dogs with unilateral otitis, only 21.43% (P<0.05) showed evidence of Malassezia. M. pachydermatis was identified cytologically and culturally in 57.53% (P<0.05), 14.29% and 30.0% of samples from the ears of dogs with otitis, from the healthy ears of dogs with unilateral otitis and from the ears of healthy dogs with no otitis. In the group with otitis associated with M. pachydermatis, the poodle was the most common breed (39.29%; P<0.05), whereas in the group without otitis, the German Shepherd breed was prominent (although this observation was not statistically significant). In both groups, the majority of dogs with M. pachydermatis were aged between 1 and 3 years (P<0.05). The higher incidence of M. pachydermatis isolated from the ears of dogs with otitis externa suggests a putative pathogenic role of this yeast in this condition.     

An idiopathic facial dermatitis of Persian cats

The clinical and histopathological features of 13 Persian cats which presented with chronic skin disease primarily affecting the face are described. Lesions were characterized by black material adherent to the skin and hair, accompanied by erythema and variable degrees of excoriation. Concurrent ceruminous otitis externa was observed in 7 cases. Histopathological examination of skin biopsy specimens showed marked acanthosis with crusting, hydropic degeneration and dyskeratotic basal epithelial cells, a mixed diffuse superficial inflammatory infiltrate and sebaceous hyperplasia. Malassezia pachydermatis yeasts and various bacteria were isolated from the lesions in some of the cats but in no case was antimicrobial therapy curative. The response to glucocorticoids was variable and often poor. No satisfactory therapeutic regimen could be identified and the cause of the disorder is unknown although a genetic basis is possible.     

Response to Malassezia pachydermatis by peripheral blood mononuclear cells from clinically normal and atopic dogs

OBJECTIVE: To investigate the potential cell-mediated immune response of atopic dogs to the yeast Malassezia pachydermatis and to correlate it with the type-1 hypersensitivity (humoral) response of the same population of dogs. ANIMALS: 16 clinically normal dogs, 15 atopic dogs with Malassezia dermatitis, 5 atopic dogs with Malassezia otitis, and 7 atopic control (ie, without Malassezia dermatitis or otitis) dogs. PROCEDURE: A crude extract of M pachydermatis was extracted for use as an intradermal allergy testing reagent and for stimulation of isolated peripheral blood mononuclear cells in vitro. Flow cytometry was also used to assess cell surface antigenic determinants (CD3, CD4, CD8, CD14, CD21, CD45RA, surface immunoglobulin) on peripheral blood mononuclear cells. RESULTS: Atopic dogs with cytologic evidence of Malassezia dermatitis had an increased lymphocyte blastogenic response to crude M pachydermatis extract, compared with clinically normal dogs and dogs with Malassezia otitis. Atopic control dogs did not differ significantly in their responses from atopic dogs with Malassezia dermatitis or otitis. A significant correlation was not found between the lymphocyte blastogenic response and the type-1 hypersensitivity response to M pachydermatis within any of the groups. CONCLUSIONS AND CLINICAL RELEVANCE: Cell-mediated and humoral reactivities to M pachydermatis contribute to the pathogenesis of atopic dermatitis in dogs but are not directly correlated. Modification of the dysregulated immune response toward M pachydermatis may assist in the reduction of pathologic changes associated with an atopic dermatitis phenotype in dogs.     

Putative Malassezia dermatitis in six goats

Histopathology submissions from 28 goats with dermatological disease were identified in an archival search of pathology files. Microscopic sections of skin biopsy specimens were examined for the presence of Malassezia spp. organisms. Six cases with many Malassezia yeasts were identified histopathologically. Based on the extent of clinical disease, three cases were regarded as localized and three were generalized infections. Clinical findings included alopecia with dry seborrhoea (four cases), greasy seborrhoea (one case), and no clinical findings specific to localized Malassezia infection when concurrent bacterial infection was present (one case). Mild pruritus was reported in two cases of generalized infection. No breed predilection was apparent. Three cases were male and three were female. Malassezia dermatitis occurred in goats from 10 months to 13 years of age. Three of six cases had concurrent bacterial infection. Skin lesions resolved following topical antifungal therapy in the two goats that were treated. Histopathological findings in all cases were severe follicular and epidermal orthokeratotic hyperkeratosis with minimal epithelial change and mild superficial perivascular to interstitial nonsuppurative inflammation. Numerous budding yeasts were visible within the stratum corneum of all cases; however, Malassezia was not isolated in the three cases in which culture was attempted. Based upon these findings, the authors suggest that the diagnosis Malassezia dermatitis in goats is most likely to be made by cytological examination of skin impressions or by examination of skin biopsy samples.     

Isolation of Malassezia species from healthy cats and cats with otitis

Lipid-dependent Malassezia species have recently been cultured from veterinary specimens. The identification of Malassezia species isolates from animals is important to clarify the epidemiology of these lipophilic yeasts. Malassezia species were cultured from the external ear canals of 63 out of 99 cats with otitis and 12 of 52 (23%) healthy control cats. The rate of isolation in affected animals versus controls was highly significant (P<0.01). Malassezia pachydermatis was isolated as a pure culture in 33 (45.2%) cats, associated with Malassezia globosa and Malassezia furfur in 20 (50%) and 17 (42.5%) animals, respectively. Three different species were isolated simultaneously in three cats (two cats with M pachydermatis, M globosa and M furfur, one subject with M pachydermatis, M furfur and Malassezia sympodialis). M globosa was isolated as the sole species in two animals. The present work confirms the presence of some lipid-dependent species of Malassezia in both healthy and otitic cats.     

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.     

Malassezia spp. overgrowth in allergic cats

A series of 18 allergic cats with multifocal Malassezia spp. overgrowth is reported: atopic dermatitis was diagnosed in 16, an adverse food reaction in another and one was euthanized 2 months after diagnosis of Malassezia overgrowth. All the cats were otherwise healthy and those tested (16 out of 18) for feline leukaemia or feline immunodeficiency virus infections were all negative. At dermatological examination, multifocal alopecia, erythema, crusting and greasy adherent brownish scales were variably distributed on all cats. Cytological examination revealed Malassezia spp. overgrowth with/without bacterial infection in facial skin (n = 11), ventral neck (n = 6), abdomen (n = 6), ear canal (n = 4), chin (n = 2), ear pinnae (n = 2), interdigital (n = 1) and claw folds skin (n = 1). Moreover, in two cats Malassezia pachydermatis was isolated in fungal cultures from lesional skin. Azoles therapy alone was prescribed in seven, azoles and antibacterial therapy in eight and azoles with both antibacterial and anti-inflammatory therapy in three of the cats. After 3-4 weeks of treatment, substantial reduction of pruritus and skin lesions was observed in all 11 cats treated with a combined therapy and in five of seven treated solely with azoles. Malassezia spp. overgrowth may represent a secondary cutaneous problem in allergic cats particularly in those presented for dermatological examination displaying greasy adherent brownish scales. The favourable response to treatment with antifungal treatments alone suggests that, as in dogs, Malassezia spp. may be partly responsible for both pruritus and cutaneous lesions in allergic cats.     

Frequency, body distribution, and population size of Malassezia species in healthy dogs and in dogs with localized cutaneous lesions.

Malassezia species are commensal organisms of human and animal skin that occasionally act as opportunistic pathogens. The lipid-dependent species are associated with human skin disorders, whereas the non-lipid-dependent species (Malassezia pachydermatis) is considered as an opportunistic secondary pathogen affecting the canine skin surface and ear canal. This study evaluated the relationship between Malassezia yeasts, their population size, and the occurrence of skin lesions from healthy and skin-diseased dogs. The efficiency of cytological examination and fungal culture for Malassezia detection was also evaluated. From March 2002 to July 2003, 33 healthy dogs and 54 dogs with pruritic localized skin diseases were examined; skin swabs (1218) were collected from 7 anatomical sites for culture and cytological examination. Malassezia prevalence according to anatomical site and the agreement between cytological results and fungal cultures were statistically analyzed. Differences in mean colony forming unit counts between positive healthy and diseased dogs were evaluated using the Bonferroni test for post hoc pair-wise comparisons. In healthy dogs, Malassezia yeasts were most frequently isolated in the perianal and perioral areas. The frequency of isolation and population size of Malassezia species were higher in dogs with localized dermatitis, especially in affected areas, indicating a role for Malassezia in the occurrence of skin lesions. Malassezia pachydermatis was the species most commonly cultured from the skin and external ear canal of healthy and diseased dogs; isolation of lipid-dependent yeasts from healthy dogs was less frequent. Using fungal culture as the gold standard, cytological examination showed good relative specificity (95%) but very low relative sensitivity (30%).     

Identification and antimicrobial susceptibility of bacteria and yeasts isolated from healthy dogs and dogs with otitis externa

The bacterial and fungal flora of the external ear canal of dogs with otitis externa and of healthy dogs were studied. The most frequently isolated microorganism from otitic ears was Staphylococcus intermedius (58.8%), followed by Malassezia pachydermatis (30.9%), Streptococcus canis (29.9%), Proteus spp. (14.4%) and Escherichia coli (10.3%). A statistical analysis of our results showed that the prevalence of these microorganisms is significant in dogs with otitis externa. Furthermore, the antimicrobial susceptibility patterns of isolated strains were determined. Majority of all bacterial isolates were most susceptible to gentamicin. Malassezia pachydermatis, the most prevalent yeast in this study, showed an excellent level of susceptibility to all antifungal agents tested.     

Malassezia otitis externa in the dog: the effect of heat-fixing otic exudate for cytological analysis

This study was conducted on 32 dogs with Malassezia otitis externa to determine the effect of heat-fixing otic exudate on cytological analysis. Malassezia infection was confirmed by cytological examination of otic exudate. Otic discharge collected with cotton swabs was then rolled onto glass slides. One slide per dog was heat-fixed prior to staining; the other slide was not heat-fixed. The number of yeast in 10 oil-immersion fields (1000 x magnification) was counted for both slides from each dog. Heat-fixing did not systematically cause either increased or decreased numbers of Malassezia on cytology of otic exudate.     

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.     

Failure of extracts from Malassezia pachydermatis to stimulate canine keratinocyte proliferation in vitro

Abstract Epidermal hyperplasia is one of the major histopathological features seen in dogs with Malassezia dermatitis. The aim of this study was to investigate the effects of extracts and culture supernatants from Malassezia pachydermatis on the proliferation of canine keratinocytes. Keratinocyte cultures were established from normal dog skin, and cell monolayers were co-cultured with Malassezia extracts (prepared either with or without protease inhibitors) and supernatants derived from organisms grown in liquid culture. The proliferation of keratinocytes was measured using a colourimetric assay. Neither the culture supernatants nor the Malassezia extracts had significant effects on the proliferation rate of canine keratinocytes, regardless of whether protease inhibitors were present or not. The results indicate that the epidermal hyperplasia seen in Malassezia dermatitis is unlikely to be caused directly by secretion of products from the organism.     

P-80 Clinical aspects of chronic progressive pastern dermatitis in Belgian draft horses

The aim of this study was to evaluate the fungi present on the skin surface in healthy horses with a particular interest in Malassezia on predisposed skin areas. Twenty-five mares were included, each sampled on nine skin areas including those most likely contaminated by Malassezia : nostrils, lips, ear pinnae, base of the mane, pasterns, pectoral areas, lateral thorax, udder and perianal areas. Two sterile carpets were applied to the skin, and then used for inoculation of agar (Sabouraud's plus cycloheximide and chloramphenicol), both with and without lipids for isolation of different species of Malassezia . This method is currently successful in isolating Malassezia in dogs. Cultures were incubated at 32°C, observed on day 5 for Malassezia , and then maintained at 27°C for complementary morphological identifications. From 223 cultures on standard medium, only seven remained sterile. The most common fungi were filamentous (number of positive samples): Scopulariopsis (156), Penicillium (79), Acremonium (67), Aspergillus (53), Paecilomyces spp. (38), and Stachybotrys (33). Interestingly, Microsporum gypseum was also isolated (14 samples from seven areas) from 10 horses. Yeast or yeast-like fungi were Geotrichum (52), Trichosporon (21), and an additional 33 samples being positive for yeast other than Malassezia . Results from the other 223 cultures on lipid-rich agar were similar. Most of the fungi were isolated from the nine areas selected, but Malassezia was never isolated from 446 cultures.
Funding: Self-funded.     

Malassezia and Candida infections in bull terriers with lethal acrodermatitis

In 12 cases of lethal acrodermatitis (LAD), four sampling techniques (brush, swab, scrape and adhesive tape strip) were used to study the distribution of yeasts in various body sites and these results were compared with those from five cases of atopic dermatitis and those of 10 normal dogs. Malassezia was frequently isolated from lesional and non-lesional skin and haircoat, footpads, nails and mucous membranes from dogs with either LAD or atopic dermatitis, although, generally, more Malassezia organisms were isolated from LAD cases. In normal dogs, Malassezia was most frequently recovered from the ear canal and the perianal skin. Candida was isolated frequently from dogs with LAD, but only a single isolate of this yeast was found in the other two groups. Fungal hyphae and pseudohyphae, probably Candida albicans, could be detected in samples collected from the nails and footpads of dogs with LAD. Both Malassezia and Candida could be isolated using all four sampling techniques. The MacKenzie (toothbrush) technique and adhesive tape strip cultures proved simple methods for the semiquantitative evaluation of yeasts. The high recovery rate of Malassezia and Candida from dogs with LAD is probably related to immune dysfunction, particularly T-cell dysfunction, known to be present in these dogs. C albicans infection may in part be responsible for the pathogenic changes of the nails and footpads commonly seen in cases of LAD.