Histopathologically, canine Malassezia dermatitis presents with variable but often marked hyperkeratosis and multifocal parakeratotic hyperkeratosis with the characteristic budding, bottle‐shaped yeasts and often cocci (if not lost during processing) over an irregular spongiotic epidermal hyperplasia that extends to the follicular infundibula, see reviews.83, 326 Exocytosis of lymphocytes is a regular feature and neutrophilic or eosinophilic exocytosis may create epidermal microabscesses. O gênero Malassezia é composto por um grupo de leveduras lipofílicas que evoluíram como comensais de pele e patógenos cutâneos oportunistas de uma variedade de mamíferos e aves. No particular subtype was associated with a collection site or a particular time‐period but multiple genotypes could colonize the same neonatal patient. Dog breeds identified to be at increased risk of Malassezia dermatitis include West Highland white terriers (WHWT), English setters, shih tzus, basset hounds, American cocker spaniels, boxers, dachshunds, poodles and Australian silky terriers. However, a region corresponding to the mating type locus (MAT) has been identified for these yeasts;6 it has been suggested that if there is an extant sexual cycle for some of them that it is more likely to be bipolar or pseudo‐bipolar, with two mating types, rather than tetrapolar as in many other basidiomycetous fungi.8, 10, On lipid‐enriched media such as modified Dixon's agar, Malassezia colonies are cream to yellowish, smooth or lightly wrinkled, glistening or dull, with the margin being either entire or lobate. The internalisation was shown to occur via binding to the mannose receptor and pinocytosis. Adverse reactions are regularly reported with the use of ketoconazole in dogs; a retrospective study of 632 dogs that received a median daily dose of 10 mg/kg reported adverse effects in 14.6%, including primarily vomiting (7.1%), anorexia (4.9%), lethargy (1.9%) and diarrhoea (1.1%).429 Adverse effects were significantly more frequent in dogs receiving concurrent ivermectin or ciclosporin. It is from these areas that Malassezia overgrowth commonly develops. with atypical strains of M. pachydermatis that show inconsistent or stable lipid‐dependence.105, 106 However, the presence of M. furfur was confirmed by molecular biology in dogs with cutaneous lesions107 or otitis108 in Brazil. Malassezia pachidermatis (97 strains) and Pseudomonas aeruginosa (42 strains) and more often as poly-infections (132 cases). Cependant, en cas de maladie cutanée, ces levures deviennent plus agressives et se multiplient en très grand nombre et provoquent une infection cutanée. The perianal skin and anal mucosa is a frequent (~55% of 73 dogs) carriage site whereas nasal and oral carriage is less frequent. Erythema, usually with kerato‐sebaceous scale, and pruritus (minimal, mild, moderate or severe) dominates the clinical presentation, often favouring intertriginous zones. Os autores serviram como Painel de Diretrizes (GP) e revisaram a literatura disponível antes de outubro de 2018. Diseases of dogs characterized histopathologicaly by parakeratotic hyperkeratosis – such as zinc‐responsive dermatosis and hepatocutaneous syndrome/superficial necrolytic dermatitis – have been anecdotally reported to promote yeast overgrowth (Section 10).247 The presence of Malassezia overgrowth is associated with pruritus in American bulldogs with autosomal recessive congenital ichthyosis caused by a single base deletion in the gene NIPAL4.248-250 In cats, a histological study of 550 skin biopsy cases identified Malassezia overgrowth most commonly with thymoma‐associated dermatosis (TAD) and paraneoplastic alopecia (PNA) associated with internal neoplasia.83 In TAD, parakeratosis is a common histopathological feature, while PNA presents either with absence of a stratum corneum or some degree of parakeratosis.83 In one cat with TAD, resolution of Malassezia dermatitis was reported to occur after its thymoma was surgically excised.251 It is important to recognize that these diseases are not typically pruritic unless Malassezia overgrowth is present. 1910: Raymond Sabouraud, a prominent medical mycologist, proposed the name Pityrosporum malassezi for this bottle shaped yeast thought to cause human dandruff.45. In 1990, Simmons and Guého described the new species M. sympodialis which was characterized by a sympodial budding process.19 In 1996, Guého et al.20 had the opportunity to collect and examine many isolates from humans and animals. Subsequently, the MDDCs underwent maturation, indicated by up‐regulation of CD83 expression and increase in expression of the co‐stimulatory molecules CD80 and CD86. Recently, genome sequencing has confirmed that M. pachydermatis lacks a fatty acid synthase gene like the other members of the genus, but is uniquely able to utilise lipid fractions within the peptone component of Sabouraud's dextrose agar for growth. Thus, yeast proliferation may be enhanced by either favourable environmental conditions (heat, humidity) and or changes in host susceptibility (Section 7). These drugs were regarded as reference agents in early studies of M. pachydermatis susceptibility to azoles because of well‐established activity against the genus,354 although polyene‐resistant strains have been induced in vitro by exposure to mutagen (N‐methyl‐N'‐nitrosoguanidine) or UV irradiation.355, Wild type M. pachydermatis strains appear routinely susceptible to nystatin, although higher MICs (MIC90 increased by a single two‐fold dilution) have been reported amongst isolates obtained from dogs with skin disease when compared to isolates from healthy dogs (reportedly RPMI1640).344 In a study of 51 strains from canine ears (supplemented Sabouraud's broth), nystatin was inferior to ketoconazole and terbinafine by seven and four two‐fold dilutions, respectively.351. SDA (preferably supplemented with 1% Tween 80) is an alternative for dogs if modified Dixon's agar is unavailable, although occasional more‐lipid dependent isolates will be overlooked with this medium; temperatures below 32°C should be avoided and use of 5‐10% carbon dioxide should be considered. This method was used previously in the quantification of staphylococci from porcine,291 human292 and canine skin and/or mucosae.293 Malassezia pachydermatis counts did not vary significantly in each of four swabs applied serially to anus and external ear canal of healthy beagle dogs; dry swabs and moistened swabs had comparable efficiency at recovering the yeast.279 Yeast counts were comparable when swab tips held in wash fluid were shaken manually or vortexed for 30 s. Utility. II. A number of investigators have evaluated the relative effectiveness of different sampling methods for Malassezia yeasts, primarily in dogs rather than cats. Cryptogamic Diseases], Uber das wesen des sogenannten Unnaschen Flaschenbazillus [The nature of the so‐called Unna's bottle bacillus], Exfoliative dermatitis in the Indian Rhinoceros (Rhinoceros unicornis) with description of a new yeast species, Pityrosporum pachydermatis, An experimental study of the pityrosporon of Malassez: its morphology, cultivation and pathogenicity, Epidermal infectiosn with yeast‐like organisms, An experimental study of the pityrosporon of Malassez: Its morphology, cultivation and pathogenicity, International Commision on the Taxonomy of Fungi (ICTF): name changes in fungi of microbiological, industrial and medical importance. It is generally recognised that Malassezia dermatitis is more common in tropical climates and during warm, humid months in more temperate latitudes, in accordance with the concept that Malassezia yeasts inhabit a ‘transitional mantel zone’ that is influenced by both host skin and the animal's external environment.87 Although not specifically studied in the dog, this factor is well‐documented in human medicine.33, The role of immunosuppression as a risk factor for Malassezia overgrowth has been discussed anecdotally,70 but no studies have examined the immunosuppressed state as a risk factor for animals with active yeast infection. and identifies areas for future development. Further evaluation of this product is warranted. The concomitant presence of the same species or the same genotypes in humans and animals is a first indication but of course it is not absolute proof unless transmission from one host to another has been clearly demonstrated. Compared with terbinafine. However, enhanced IgG responses can be seen in dogs with Malassezia dermatitis and in humans and dogs with atopic dermatitis. However, a correlation between the onset of Malassezia dermatitis (or otitis) and the recent use of antibacterial drugs is sometimes observed by practitioners and could reflect a reduction in “competition” for micro‐ecological resources as the bacterial population is reduced.241 However, the opposite has also been noted for individual dogs, where yeast counts dropped following treatment with cefalexin.146. Molecular techniques are pivotal in the accurate identification of many of the currently recognised Malassezia species, with the usual exception of M. pachydermatis (which is readily distinguished from the other species by growth on Sabouraud's dextrose agar). WAVD cannot be held responsible for errors or any consequences arising from the use of information contained in this article. Factors such as important variations in anatomical site, breed, sampling method and host immune status commonly thwart the interpretation of the clinical significance of an observed population (“XX yeasts in YY fields”); trial therapy is routinely required to establish this (Sections 8.5 and 14.1–3-14.1–3). Methods for microbiological assessment of skin populations have traditionally included impression (cytology using slides or tape; culture) and dispersal (primarily cup‐scrub or swab‐wash) methods.261 Impression culture methods tend to under‐estimate microbial populations whereas dispersal methods yield values closer to the true population.262, 263 Cytological examination without impression (scrapings, swab samples) are more recent developments. Microbiome studies utilising next‐generation sequencing have the potential to re‐define the microbial ecology of mammalian skin. Analysis of the history of scientific discovery highlights the influence of language and geography, the role of experts and opinion leaders in study centres or in the modern day “centres of excellence”, and wider cultural effects that may impede or enhance investigation and implementation of technological advances in the pursuit of scientific progress. Further studies are therefore required to determine the precise role played by these antibodies in Malassezia‐induced skin disease. The superficial dermis has variable oedema with interstitial and perivascular inflammation of lymphocytes (usually the dominant cell type), plasma cells, histiocytes, neutrophils and eosinophils. Despite the undisputable value of this phenotypic identification scheme, ambiguous results are sometimes reported. The remaining species were detected across other body sites and with lower frequency.121 Reanalysis of these metagenomic datasets using a more complete set of Malassezia genomes demonstrated the presence of 12 species, with M. restricta and M. globosa by far the most abundant, distantly followed by M. sympodialis.8 The metagenomic analysis of skin samples from 40 asymptomatic individuals in Hong Kong revealed that 90% of the sequencing reads matched to M. restricta.123 Another study investigating 40 asymptomatic individuals in Japan indicated that Malassezia population differed by sex, body part and season.124 Another study reported a significant decrease in community diversity as an indication of skin disease in humans.125, Only a very few studies examined the skin microbiota in dogs and cats.117, 118, 126-128 One study suggested that the main force driving the variability in microbiota composition was the individual, rather than the breed, hair coat or the skin site.126 Anotherh study used NGS to define a much more diverse cutaneous mycobiota than that previously described with culture‐based techniques in studies of healthy and allergic dogs.118 The cutaneous mycobiota appeared to be influenced by various factors including environmental exposure, cohabitation with other pets and skin health status. isolates from human clinical specimens collected in 1984 at the Center for Disease Control in Atlanta (USA) 15 were identified as M. pachydermatis.463 These last isolates were mainly from skin, tissue fluids (e.g. Our review includes a full description of the genus, since six of the currently recognised species have been described on dogs and cats, and six more have been described in other species encountered by veterinary practitioners. In a survey in Slovakia, mycological cultures performed from dogs with cutaneous lesions (n = 118) and dogs with otitis externa (n = 328) yielded M. pachydermatis as the most frequently isolated species (121 isolates); however, four lipid‐dependent isolates were identified as M. furfur and one as M. nana.109, The skin of Felidae is colonized by a diverse array of Malassezia spp yeasts. Marked sequence diversity of the intergenic spacer (IGS)(Figure S1 and S2) of M. pachydermatis isolated from dogs and cats enabled identification of three major groups (1, 2, 3) with 10 subtypes (1A, 1B, 1C, 1D, 2A, 2B, 3A, 3B, 3C and 3D).313 In Japan, Korea and Taiwan, isolates of M. pachydermatis of subtype 3D were obtained more frequently from cAD skin lesions than from healthy canine skin.314 Moreover, subtype‐3D strains isolated from atopic dermatitis skin produced higher amounts of phospholipase A2 than did strains of other genotypes, supporting the hypothesis that the pathogenicity of this yeast is associated with the production of high levels of phospholipase A2.157 By contrast, lack of sequence diversity in the IGS region of M. nana isolates,111 and in the ß‐tubulin gene and microsatellite profiles112 indicate that a particular M. nana genotype predominates in cats. Furthermore, the addition of recently identified species resulted in similar physiological patterns and thus in a doubtful identification (M. arunalokei and M. brasiliensis are closely related to M. restricta and M. furfur, respectively) (Table S1). Amongst Malassezia spp., M. pachydermatis is the least fastidious and normally grows readily on routine media such as SDA,106 although M. pachydermatis variants with more‐exacting lipid requirements have been isolated.105, 300, 301, In early qualitative studies, the addition of 1% Tween 80 to a dextrose/ yeast extract agar enhanced the isolation of M. pachydermatis.302 Tween 80 was not needed for the selective and differential isolation of M. pachydermatis in the presence of peptone,303 now recognised as the essential lipid source for growth of that species on SDA.18, 106 Malassezia pachydermatis was isolated from swab wash samples in comparable numbers after three and seven days of incubation at 32°C on each of five media; SDA, SDA plus 1% Tween 80, Ushijima's medium A, modified Dixon's agar and Leeming's medium.280 After three days of incubation, the colonies were most distinctive on modified Dixon's agar, forming buff‐coloured domed colonies 1–1.3 mm in diameter that were readily distinguished from other cutaneous microbes; on other media the colonies were low convex. 1928–1929: McLeod and Dowling part‐fulfilled Koch's postulates by isolation of M. furfur from humans with seborrhoeic dermatitis in an oleic acid broth.48, 49 They then inoculated lesion‐free skin of a person with seborrhoeic dermatitis and a normal human with the broth isolate and reproduced seborrhoeic lesions in both, from which they re‐isolated M. furfur. Die Malasseziendermatitis bei Hunden und Katzen hat sich von einer obskuren Erkrankung mit Kontroversen in Bezug auf ihre Existenz zu einer heute routinemäßigen Diagnose in der allgemeinen Veterinärpraxis entwickelt. Feline facial acne, thought to represent an idiopathic disorder of follicular keratinization, may also result in Malassezia overgrowth.252, The skin surface presents a range of natural micro‐climates and several ecological niches with different moisture and nutrient levels may be recognised.253 The eyes, ears, nares, oral cavity, lip fold, prepuce, vagina and anus provide microenvironments that are moist with secretions and constitute unique ecological niches (Section 4). More recently, the spectrum of fungal species (“mycobiome”) in the human skin was investigated using next generation sequence techniques.121 In this study, 14 skin sites representing a range of physiological characteristics were sampled from 10 healthy adult volunteers. The outbreak resolved upon implementation of infection control measures, including withdrawal of lipid‐rich hand moisturisers from staff. Subsequent studies by the same group and other groups in Spain and Japan led to reports on the isolation of M. globosa,76 M. furfur,77, 78 M. nana24, 79 and, more recently, M. slooffiae80-82 from domestic cats. Interaction with other commensal microbes might also influence pathogenicity and expression of virulence factors.138-140 Thus, these commensal yeasts are likely highly regulated by continuous interactions with the host immune system (Section 6)141 and these interactions ultimately determine whether the outcome is inflammation (i.e. Conflicts of Interest: : In the past five years, Ross Bond has received funding from or otherwise collaborated with Dechra Veterinary Products, Bayer Animal Health, Ceva Animal Health, MSD Animal Health and Elanco. The genus Malassezia is comprised of a group of lipophilic yeasts that have evolved as skin commensals and opportunistic cutaneous pathogens of a variety of mammals and birds. Scientists have been grappling with the complexity of the genus Malassezia and their associated diseases for decades. Compounded formulations must be avoided due to unreliable bioavailability. Concurrent use of cefalexin in both treatment groups limits full clinical interpretation (LoE 2; SoR B‐moderate). Of these cats, four received ketoconazole 10 mg/kg for 14–42 days either alone (2/4 cases) or with concurrent antibiotics (two of four cases). Malassezia pachydermatis has also been isolated with significantly higher prevalence from the sputum of asthmatic human patients (21.7%) than from healthy controls (0%).468 The clinicopathologic significance of this finding, if any, is unknown and data on pet ownership was not collected from the subjects studied. Of these, to date, M. pachydermatis, M. furfur, M. sympodialis, M. globosa, M. slooffiae, M. nana, M. caprae, M. equina, M. cuniculi, M. brasiliensis, M. psittaci and M. verspertilionis have been isolated from animals and are therefore relevant in veterinary dermatology (Table 1). These include plant‐derived substances such as Blad‐containing oligomer (an antifungal agent approved for agricultural use);364, 365 beta‐thujaplicin,351 a honey‐based gel,366 kanuka and manuka367 and other plant‐derived essential oils;368 agents primarily used in the topical treatment of human dandruff or seborrhoeic dermatitis (selenium sulphide, zinc pyrithione, ciclopiroxolamine,369 rilopirox370) and povidone–iodine.371 The calcineurin inhibitors (tacrolimus and pimecrolimus) have activity in vitro against human‐associated Malassezia yeasts.372 The clinical relevance of these observations for canine and feline infections requires further assessment. Interestingly, Swiss white mice developed skin lesions whereas the nude (nu/nu) mouse, the hairless mice and nude rats did not.321 Inoculation of suspensions of M. pachydermatis into the middle ear and dermis of immunosuppressed mice led to transient infection that resolved within 21 days.325. Concurrent cefalexin limits interpretation. The basset hound and WHWT in particular demonstrate clinically distinctive conditions characterized by generalized seborrhoea (basset hound)98, 145 or generalized, severely pruritic dermatitis with marked lichenification and hyperpigmentation.243 It is noteworthy that all of these breeds are recognized to be at increased risk for developing ether atopic dermatitis or primary idiopathic seborrhoea. Si vous souhaitez lire plus d'articles semblables à Comment traiter la dermatite chez mon chien , nous vous recommandons de consulter la catégorie Animaux de compagnie . The issue of yeast number is compounded by the potential for hypersensitivity responses to Malassezia allergens to exaggerate the immunological reaction out of proportion to the population density of the yeast (see Section 6). Malassezia, une levure présente sur la peau du chien. Despite this, no correlation has been found between Malassezia‐specific serum IgG concentration and atopy patch test responses to the yeast in patients with atopic dermatitis.63, 197 It is therefore considered that determination of Malassezia‐specific IgG concentrations has little value in the diagnosis of Malassezia sensitization in atopic human patients.178, 197 However, concentrations of IgG4, a subtype that is induced in Th2 responses, are correlated with IgE concentrations in atopic patients with sensitivity to Malassezia sympodialis.205, In atopic dogs with or without cytological evidence of M. pachydermatis overgrowth, there are significantly higher serum titres of Malassezia‐specific IgG than those seen in healthy dogs.206 However, there was no significant difference between atopic dogs with or without Malassezia overgrowth. One study identified Malassezia yeasts in 43 out of 52 healthy cats sampled in the winter months in north eastern USA.113 By contast, another study failed to identify yeasts in 20 health cats sampled in France; notably in the latter study, the presence of cerumen was an exclusion criterion whereas cerumen was noted in many of the US cats, especially amongst those with a purely indoor lifestyle.114 Malassezia yeasts were detected in 20% (six of 30) ear canals of 15 cats with disease and in 43% (13 of 30) ear canals of 15 allergic cats.114 Devon rex cats and sphynx cats, but not Cornish rex cats, are prone to high carriage rates of Malassezia yeasts and a generalised seborrhoeic dermatitis that responds to oral itraconazole.80, 86, 115, 116 Predisposing factors such as hypersensitivities and internal diseases that disrupt cornification are reviewed in Section 7. The chronic lesions are characterised by symmetrical areas of intense hyperpigmentation, severe lichenification, erythema and tightly adherent crust. It is intuitive that evidence of immediate, IgE‐mediated or cellular hypersensitivity might indicate the need for rigorous antifungal therapy to minimize allergen challenge in the sensitized host, although this remains to be proven by controlled therapeutic studies. However, it is known that both chlorhexidine and polyhexanide have excellent in vitro activity against M. pachydermatis.480 In addition, improved hand‐washing practices eliminated an endemic problem with M. pachydermatis infections in a NICU.469. Malassezia antigens triggered significantly higher PBMC responses in atopic people compared to healthy individuals193-196 and this effect has also been demonstrated in atopic dogs.190 In P. orbiculare [syn. Yeasts of Emerging Concern in Fungemia. 1970: The systematics were rectified when Sloff in Lodder's ‘The Yeasts, a taxonomic study’ assigned all Pityrosporum that grew on media without lipid enrichment as single species of P. pachydermatis.52, 1984: The third edition of “The Yeasts, a Taxonomic Study” (Yarrow and Ahearn) referred to the new genus Malassezia and confirmed that one species grew without lipid enrichment.53, 54 This was later officially added into the taxonomical order.55, 1990: A new species, Malassezia sympodialis was described19 and by 1996 four new species were added to the genus.20 This species was later isolated from a cat by Bond et al. Complete clinical & mycological response ‐ diagnose, Partial clinical, complete mycological ‐ diagnose. O GP preparou uma revisão detalhada da literatura e fez recomendações sobre os tópicos selecionados. isolation from the hair coat as compared to non‐infected cats.254, Antibacterial therapy has not been reported to be an independent risk factor for development of Malassezia dermatitis in any published studies. Case series of Malassezia dermatitis in cats treated with oral itraconazole. Table S3. Miconazole is an azole derivative present in various shampoos, creams or lotions. Additional diagnostic evaluations and treatments may be indicated at first presentation depending on the clinical signs, including cases where signs suggest, for example, paraneoplastic disorders in cats. IgM, IgG and IgA antibodies against Malassezia species are present in both young and elderly people, but the amount of IgG and IgM tends to tail off with age corresponding with declining numbers of commensal yeasts.200-202 The Malassezia‐specific IgA concentration was found to be relatively low in all age groups. Cytology using swabs is normally best restricted to use in the ear canal. Different studies targeted various RNA or DNA regions in order to distinguish the molecular pattern of M. pachydermatis and to assess whether genotype classification was in accordance with host preferences. In recent years methods based on next generation sequencing (NGS) have allowed a better characterization of the complex microbial communities occurring on the skin and made it possible to detect Malassezia species that would otherwise be missed using culture‐based methods (Section 4.4).
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