Malassezia Dermatitis Research Articles

The biology ofMalasseziaorganisms and their ability to induce immune responses and skin disease

TABLE OF CONTENTSIntroduction 4History and taxonomy of the genusMalassezia 5Biological characteristics ofMalasseziaorganisms 5Structure 5Reproduction 6Biochemistry 6Distribution ofMalasseziaorganisms on the host 6Immunological and epidermal responses toMalasseziaorganisms 7The immune response toMalasseziaorganisms 7Antigen release, penetration and presentation 8Cell‐mediated immune responses 8IgG, IgM and IgA responses toMalasseziaorganisms 9IgE responses toMalasseziaorganisms 10Mast cell responses 11Epidermal responses associated withMalasseziadermatitis 12Malasseziaorganisms as pathogens in humans and animals 13Diseases associated withMalasseziaspp. in humans 13Pityriasis versicolor 13Malasseziafolliculitis 13Seborrheic dermatitis and dandruff 14Atopic dermatitis 14Malasseziafungaemia 14Diseases associated withMalasseziaspp. in animals 15Malasseziadermatitis in dogs 15Predisposing factors for overgrowth ofMalassezia pachydermatis 15Pathogenesis 16Clinical features 16Diagnosis 17Treatment 18Conclusions 19References 19

FC‐5 Unsaturated transferrin inhibits the growth of Malassezia pachydermatis in vitro

Transferrin, an iron‐binding protein that transports iron to mammalian cells, may contribute to innate immunity to fungal pathogens, primarily by limiting microbial access to iron. We investigated whether unsaturated (apo)‐transferrin had an inhibitory effect in vitro on Malassezia pachydermatis, an important opportunistic cutaneous yeast pathogen of dogs. M. pachydermatis strains were grown at 32°C in medium containing canine or bovine apo‐transferrin at concentrations of 0.7, 1.3, 2.7 and 5.3 mg/mL. Optical density (OD492) was measured daily until growth was stationary (day 6) in saline‐control wells and then compared between treatments by ANOVA and Tukey's tests. Bovine and canine transferrin inhibited (P < 0.01) yeast growth at all concentrations tested. Using bovine transferrin, the mean OD ± SE for 10 strains were: saline, 0.55 ± 0.19; 0.7 mg/mL, 0.33 ± 0.05; 1.3 mg/mL, 0.18 ± 0.03; 2.7 mg/mL, 0.18 ± 0.04; 5.3 mg/mL, 0.16 ± 0.03. Using canine transferrin, the mean OD ± SE for seven strains were: saline, 0.79 ± 0.03; 0.7 mg/mL, 0.37 ± 0.07; 1.3 mg/mL, 0.27 ± 0.04; 2.7 mg/mL, 0.24 ± 0.03; 5.3 mg/mL, 0.20 ± 0.03. For both bovine and canine transferrin, inhibition by 5.3 mg/mL exceeded (P < 0.05) that of 0.7 mg/mL. Since both bovine and canine apo‐transferrin inhibit the growth of M. pachydermatis in vitro, serum transferrin may contribute to innate immunity to M. pachydermatis indogs and cattle. The spongiotic dermatitis reaction seen histologically in many dogs with Malassezia dermatitis may promote the accumulation of transferrin at infection sites. Funding: Self‐funded.

Hereditary nasal parakeratosis in Labrador retrievers: 11 new cases and a retrospective study on the presence of accumulations of serum ('serum lakes') in the epidermis of parakeratotic dermatoses and inflamed nasal plana of dogs.

We report 11 new cases of hereditary nasal parakeratosis in Labrador retrievers. The disease was first observed when the dogs were 6 months to 2 years of age, and affected dogs of either sex and all coat colours. Hyperkeratosis and depigmentation were confined to the nasal planum, and affected dogs were otherwise healthy. The principal histological findings in biopsy specimens were marked diffuse parakeratotic hyperkeratosis, multiple intracorneal serum lakes and superficial interstitial-to-interface lymphoplasmacytic dermatitis. Topical applications of propylene glycol in water or white petrolatum were often effective for treatment of the dermatosis. However, continued applications were required to maintain a beneficial response. A retrospective histological study of parakeratotic inflammatory diseases of canine haired skin and inflammatory diseases of the canine nasal planum was performed. The degree of parakeratotic hyperkeratosis and the number and size of intracorneal serum lakes were evaluated. The degree of parakeratotic hyperkeratosis was greater in hereditary nasal parakeratosis specimens than that seen in discoid lupus erythematosus and Malassezia dermatitis. There were more serum lakes in hereditary nasal parakeratosis specimens than in specimens from dogs with discoid lupus erythematosus, Malassezia dermatitis, primary seborrheic dermatitis or zinc-responsive dermatosis. Significant differences in sizes of serum lakes (if present) were not seen.

Evaluation of serum obtained from atopic dogs with dermatitis attributable to Malassezia pachydermatis for passive transfer of immediate hypersensitivity to that organism

To determine the functionality of canine anti-Malassezia IgE via the passive transfer of immediate hypersensitivity localized to the skin (ie, cutaneous anaphylaxis) from atopic dogs with dermatitis attributable to overgrowth of Malassezia pachydermatis (Malassezia dermatitis [MD]) to healthy recipient dogs by use of the Prausnitz-Küstner (P-K) technique. 7 clinically normal dogs, 32 atopic dogs with MD, serum from 11 atopic dogs with MD, and 3 healthy dogs without prior sensitization to M pachydermatis. Serum from atopic dogs with MD was used for P-K tests in 3 clinically normal recipient dogs. Serial dilutions of untreated, heat-inactivated, IgE-absorbed, and bovine serum albumin (BSA)-absorbed (control) aliquots of serum were injected ID in triplicate for dermal sensitization. Twenty-four, 48, and 72 hours later, a crude extract of M pachydermatis was injected ID into the sites used for sensitization injections, and immediate hypersensitivity reactions were graded on a 4-point scale. Untreated serum caused P-K reactivity beginning 24 hours after passive sensitization and persisting through 72 hours (titers, 1:32 to 1:64). Heat inactivation and IgE-absorption of serum eliminated P-K reactivity, whereas treatment of serum with BSA did not. Analysis of P-K test results supports the passive transfer of cutaneous anaphylaxis by anti-Malassezia IgE and indicates it is functional in type-1 hypersensitivity reactions of atopic dogs with MD. Reduction or blockade of anti-Malassezia IgE in atopic dogs with MD may provide better clinical control of the disease.

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

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.

Macroscopic, cytological and bacteriological evaluation of anal sac content in normal dogs and in dogs with selected dermatological diseases.

Macroscopic and cytological aspects of anal sac content were evaluated in 40 normal dogs and 10 dogs each with pyoderma, Malassezia dermatitis associated with atopic dermatitis and uncomplicated atopic dermatitis. Bacteria isolated from anal sacs were compared with those from abdominal skin and hair in 20 normal dogs and 10 dogs with pyoderma. There was no difference between the groups in anal sac dimension, or in the colour, consistency or presence of granules in their content. Extracellular bacteria were found in higher numbers in diseased animals, whereas intracellular bacteria were observed in 40% of dogs with pyoderma and in only 2.5% of normal dogs. Malassezia spp. were present in 15.7% of dogs, with no difference between groups. Neutrophils were observed in 12.5% of normal dogs, 30% of dogs with Malassezia dermatitis with underlying atopic dermatitis and in 70 and 80% of dogs with pyoderma and uncomplicated atopic dermatitis, respectively. Seven bacterial species were isolated from anal sacs, with no difference between normal dogs and dogs with pyoderma. In five normal animals and in four dogs with pyoderma the same bacterial strains were isolated from anal sacs and from abdominal skin and hair.

Transfer of passive cutaneous anaphylaxis to Malassezia pachydermatis by the serum of atopic dogs with Malassezia dermatitis

In atopic dogs with Malassezia dermatitis (MD), type 1 hypersensitivity reactions and circulating serum IgE reactive to M. pachydermatis extracts have been reported. The purpose of this study was to evaluate the functionality of anti‐Malassezia IgE by the transfer of passive cutaneous anaphylaxis (PCA testing). Three nonatopic dogs were used as recipients. Two test sera were utilized: pooled sera from 10 atopic dogs with MD that were skin test positive to M. pachydermatis extract; and serum from an atopic dog with MD that exhibited high levels of anti‐Malassezia IgE on an ELISA assay. One aliquot of each untreated serum, one aliquot of each serum heated at 56 oC for 4 h and two aliquots of the ELISA‐positive serum adsorbed with either mouse anticanine IgE or bovine serum albumin (as a control) were utilized. Six serial dilutions of all six aliquots were injected intradermally in triplicate, along with a 20 µg mL−1 extract of M. pachydermatis to rule out prior sensitization to the yeast. At 24‐, 48‐ and 72‐h intervals, the yeast extract was injected intradermally at the sites of prior serum injections and wheal/flare responses were graded 0–4+ compared with saline and histamine controls. Through 72 h, all dogs showed > 2+ reactions at the injection sites of both the untreated sera and the BSA‐treated sera (titers = 1:64), but no reactions at the sites of heat‐inactivated and IgE‐adsorbed sera. These results support the transfer of PCA by anti‐Malassezia IgE and implicate it to be functional in type 1 hypersensitivity. Funded by the Canine Health Foundation of the American Kennel Club.

Intradermal test reactivity to Malassezia pachydermatis in healthy basset hounds and basset hounds with Malassezia dermatitis

Nineteen healthy beagles, eight healthy basset hounds and 17 basset hounds with Malassezia dermatitis weretested intradermally with two extracts of M pachydermatis. One healthy beagle and two affected basset houndsshowed...

Identification of major allergens of Malassezia pachydermatis in dogs with atopic dermatitis and Malassezia overgrowth.

We have previously shown that both atopic and normal dogs generate an IgG response to antigens of Malassezia pachydermatis. The aim of this study was to compare IgE responses to separated proteins of M. pachydermatis in 28 atopic dogs with Malassezia dermatitis and 22 clinically normal dogs using Western immunoblotting. Six different detection systems were evaluated in order to assess sensitivity and eliminate nonspecific binding and cross-reactivity. The protocol yielding the best results utilized a monoclonal mouse antidog IgE, an alkaline phosphatase conjugated goat antimouse IgG which had been passed through a canine IgG column 3 times, a chemiluminescent substrate and a digital imaging system. Proteins of 45, 52, 56 and 63 kDa were recognized by more than 50% of the atopic dog sera and thus represented major allergens. Only a minority of normal dogs showed faint IgE binding to these proteins. The results indicate that the majority of atopic dogs with Malassezia dermatitis have a greater IgE response than normal dogs, suggesting an IgE-mediated immune response may be clinically important in the pathogenesis of the disease.

Immunoglobulin G responses to Malassezia pachydermatis in healthy dogs and dogs with Malassezia dermatitis

Serum immunoglobulin G (IgG) responses of healthy dogs and dogs with Malassezia pachydermatis dermatitis were compared by Western immunoblotting. M pachydermatis CBS 1879 was disrupted mechanically and its proteins were...

Intracorneal vacuoles in skin diseases with parakeratotic hyperkeratosis in the dog: a retrospective light-microscopy study of 111 cases (1973-2000).

Two recent case reports described a congenital keratinization defect (congenital follicular parakeratosis; CFP) in Rottweiler and Siberian Husky dogs. Skin biopsy specimens revealed marked parakeratosis targeting the hair follicle and numerous intracorneal vacuoles. A retrospective histopathological study was conducted on skin biopsy specimens from 111 dogs with diseases associated with parakeratotic hyperkeratosis to determine whether intracorneal vacuoles were present. Additional criteria evaluated were the size and location of the vacuoles and the degree of parakeratosis. Cases examined included dogs with primary idiopathic seborrhoea, necrolytic migratory erythema (NME), Malassezia dermatitis, zinc-responsive dermatosis, hereditary nasal hyperkeratosis of Labrador Retriever dogs, thallotoxicosis and CFP. Thirty-seven cases (37/111, 33%) had intracorneal vacuoles, including nine cases of primary idiopathic seborrhoea (9/29, 31%), 10 cases of NME (10/18, 56%), five cases of Malassezia dermatitis (5/19, 26%), five cases of zinc-responsive dermatosis (5/36, 14%), five cases of hereditary nasal hyperkeratosis (5/5, 100%) and three cases of CFP (3/3, 100%). If present, intracorneal vacuoles were found throughout all layers of the parakeratin. The sizes of intracorneal vacuoles varied among diseases, but large (> 5 microm) vacuoles only were present in CFP. Biopsies with a larger degree of parakeratosis were significantly more likely to have intracorneal vacuoles (P = < 0.001). Based on this study, intracorneal vacuoles are a common finding in many parakeratotic skin diseases of the dog, but large (> 5 microm) vacuoles are found only in CFP.

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.

Subepidermal linear alignment of mast cells in inflammatory dermatoses of the dog.

A recent study demonstrated that 47.7% of dogs with Malassezia dermatitis had a subepidermal linear alignment of mast cells (SLAM). A retrospective histopathological study was conducted on 419 canine skin biopsies to determine if a SLAM was present in other inflammatory diseases. Cases examined included dogs with demodicosis, sarcoptic mange, dermatophytosis, pemphigus foliaceus, pemphigus erythematosus, discoid lupus erythematosus, systemic lupus erythematosus, erythema multiforme, dermatomyositis, staphylococcal pyoderma, primary seborrhea, arthropod bites, contact hypersensitivity, flea bite hypersensitivity, atopy, and food hypersensitivity. Three cases (3/419, 0.7%) were identified with SLAM. The diagnoses for these cases were atopy (1/23, 4%) with a secondary bacterial folliculitis (1/136, 0.7%), pemphigus erythematosus (1/18, 6%), and discoid lupus erythematosus (1/16, 6%). Based on this study, SLAM is significantly more common in Malassezia dermatitis than in other inflammatory diseases.

Canine atopic dermatitis in Greece: clinical observations and the prevalence of positive intradermal test reactions in 91 spontaneous cases

Atopic dermatitis was diagnosed in a total of 91 dogs by combining the compatible historical evidence and clinical signs with the presence of one or more positive intradermal test reactions well correlated with the exposure to the aeroallergens and the seasonality of the clinical signs. Compared to the general hospital population Yorkshire terriers, Chinese Shar-Peis and cocker spaniels showed a strong predilection. No such predilection was found regarding the sex of the animals. The age of the dogs at the onset of the clinical signs ranged from 2 months to 8 years (median: 2.5 years). Moderate to severe pruritus, noticed in all the 91 dogs, was either localized (29/91) or generalized (64/91) and non-seasonal (43/91), seasonal (19/91) or of unknown seasonality (29/91). The most common cutaneous lesions included erythema, hyperpigmentation, hypotrichosis and crusts; their body distribution was generalized (64%) or localized (36%) with the feet as the most common site of involvement. Five dogs that had unlesional skin were significantly younger and had been pruritic for a shorter period of time compared to the majority of our study population. Otitis externa (43/91) and bacterial pyoderma (30/91) were the most common conditions associated with atopic dermatitis, while the prevalence of Malassezia dermatitis was very low (2/91). Of the other allergic skin diseases flea allergic dermatitis was the most common (29/91) followed by food hypersensitivity (2 out of the 15 dogs tested). The majority of the dogs demonstrated multiple sensitivities to the 50 aeroallergens tested, while domestic mites (77/91), and particularly Dermatophagoides farinae (64/91), were the most commonly implicated. The total number of the positive intradermal test reactions was increasing parallel to the age of the dogs but it was negatively associated with the presence of skin lesions on the carpal and tarsal joints.

Humoral and cell-mediated responses to Malassezia pachydermatis in healthy dogs and dogs with Malassezia dermatitis

The in vitro proliferative responses of peripheral blood mononuclear cells from seven healthy basset hounds exposed to Malassezia pachydermatis antigen (500 μg/ml) exceeded (P<0.05) those of seborrhoeic basset hounds with...

Type-1 hypersensitivity reactions to Malassezia pachydermatis extracts in atopic dogs

SUMMARY Objective To investigate the potential allergenic role of the yeast Malassezia pachydermatis in dogs with clinical diagnosis of atopic dermatitis. Animals 5 clinically normal nonatopic dogs, 10 atopic dogs with cytologic evidence of Malassezia dermatitis, and 12 atopic dogs without cytologic evidence of Malassezia dermatitis. Procedure A crude yeast extract was produced by disrupting the cell wall of M pachydermatis. The crude extract and 8 of its fractions, which were generated by fractionation in a high-performance liquid chromatography column, were injected along with 46 commercial allergens for intradermal allergy testing of normal and atopic sample populations. Significant difference between atopic populations was evaluated, using a threshold concentration of crude yeast extract that failed to induce wheal-and-flare responses in normal nonatopic dogs. Results Atopic dogs with cytologic evidence of Malassezia dermatitis had significantly greater wheal-and-flare reactions to intradermal injection of crude extract of M pachydermatis than did atopic dogs without cytologic evidence of Malassezia dermatitis. Conclusions It is concluded that M pachydermatis is capable of promoting type-1 hypersensitivity reactions in dogs with an atopic dermatitis phenotype. Clinical Relevance Currently, Malassezia dermatitis is principally managed by use of antifungal chemotherapy. Because the yeast appears to be a contributing allergen in dogs with atopic dermatitis, hyposensitization with M pachydermatis extracts may offer a future alternative to extended or repeated episodic administration of antifungals for extended control of recurrent infections. (Am J Vet Res 1998;59:836–841)

Malassezia dermatitis in the dog: a retrospective histopathological and immunopathological study of 86 cases (1990-95).

A retrospective histopathological and immunopathological study was conducted on 86 dogs with Malassezia dermatitis. West Highland White terriers, English Setters, Shih Tzus, Basset Hounds, American Cocker Spaniels, spayed females, and castrated males were found to be at increased risk. The histopathological reaction pattern of lymphocytic superficial perivascular to interstitial dermatitis with parakeratotic hyperkeratosis, irregular epidermal hyperplasia, diffuse intercellular oedema and lymphocytic exocytosis was found to be consistent with a diagnosis of Malassezia dermatitis whether yeast were histologically visible (73.3% of the cases) or not (26.7%). Immunopathological studies revealed that 60- > 90% of the inflammatory cells within the epidermis, and 25-75% of those within the dermis were CD3+T lymphocytes, and that the only immunoglobulin-positive cells were dermal plasma cells.

Skin and mucosal populations of Malassezia pachydermatis in healthy and seborrhoeic Basset Hounds.

Quantitative and semiquantitative cultural techniques were used to study skin and mucosal carriage of Malassezia pachydermatis in 20 healthy mixed-breed dogs, 13 healthy Basset Hounds and 33 seborrhoeic Basset Hounds. The frequencies of isolation and population sizes from the axilla, nose, mouth and vulva were significantly greater (P < 0.01) in both groups of Basset Hounds when compared with the healthy mixed-breed dogs. Population sizes in the seborrhoeic Basset Hounds exceeded those of the healthy bassets at the nose (P < 0.05), vulva (P < 0.01) and axilla (P < 0.001). However, the frequencies of isolation and population sizes of the yeast from the anus were comparable in the three groups of dogs. The relatively high skin and mucosal populations in healthy Basset Hounds may explain, in part, the predisposition to 'Malassezia dermatitis' in this breed. However, the factors which enable the yeast to establish such high populations in Basset Hounds remain unclear.

Quantity and distribution of Malassezia organisms on the skin of clinically normal dogs

Objective To define the extent to which Malassezia organisms can be recovered from the skin of clinically normal dogs and to assess differences in organism recovery related to anatomic sampling site and to method of collection. Design Prospective, controlled study. Animals 19 clinically normal dogs. Procedure The number of Malassezia pachydermatis organisms were determined in fungal cultures of samples obtained from the skin of clinically normal dogs, using an adhesive tape method to obtain samples from 10 sites/dog. Additionally, 3 methods (direct impression, swabbing technique, and superficial skin scraping) that are commonly used for obtaining samples for cytologic examination were evaluated. Results Malassezia organisms were found in low numbers as part of the microflora of the skin of clinically normal dogs. Number of organisms differed significantly for various anatomic locations (chin, highest number; inguinal and axillary regions, lowest number). Malassezia organisms were identified more frequently by use of adhesive tape and fungal culturing than by the methods used for cytologic examination. However, comparing methods used for obtaining samples for cytologic examination with each other, marked differences were not detected in our ability to recover yeast organisms among the 3 techniques. Clinical Implications Although Malassezia spp is part of the microflora of the skin of clinically normal dogs, it is extremely difficult to detect the organism by any of the 3 sampling methods used for sample collection for cytologic examination. Therefore, anatomic site and method of sample collection should be considered when attempting to make a diagnosis of Malassezia dermatitis. (J Am Vet Med Assoc 1996;208:1048–1051)