Pathological and clinical aspects of the diseases caused by Malassezia species

From veterinary point of view Malassezia pachydermatis has the greatest significance. It has been standing in the focus of interest since the early 1990s, mostly because of the frequency of otitis externa and dermatitis caused by this yeast in dogs. This is the only lipid-independent species in the genus Malassezia. It can be found in very large proportion on the skin of healthy animals, but can be isolated in much greater number from diseased dogs. It often causes illness together with other pathogens (e.g. Staphylococcus intermedius). Some breeds are predisposed. In addition to the treatment of the accidental concurrent diseases, therapy consists of systemic and/or topical antimicrobial treatment. Ketoconazole is used most frequently. Malassezia pachydermatis plays also a role in the skin disorders of other carnivores. It has little zoonotic potential, it can be dangerous to immunocompromised humans. The other Malassezia species have little veterinary importance, although M. sympodialis and M. globosa were isolated from asymptomatic animals (mostly cats) and from mixed infections.     

The status of corticosteroid therapy in dermatology

Therapy with systemic corticosteroids, despite attendant serious risks, is mandatory in diseases such as pemphigus, acute disseminated lupus erythematosus and some cases of exfoliative dermatitis that are ordinarily fatal, for in such cases life may be prolonged and the patients made comfortable. If no contraindications exist, therapy with corticosteroids is desirable, for diseases of short duration-contact dermatitis, serum sickness reactions and drug eruptions of all kinds-provided the causative factors have been removed and the reactions are causing severe distress.On the basis of encouraging reports in the literature corticosteroid therapy may be instituted with justification for a group of unrelated, intractable and discomforting diseases such as maddening pruritus ani, sclerema neonatorum, dermatomyositis, certain cases of sarcoidosis, berylliosis, Behcet's syndrome, universal calcinosis, Reiter's disease and ulcers of sickle-cell anemia. One must always bear in mind the well-defined contraindications to corticosteroid therapy and the hazards of its use, particularly if therapy is to be prolonged. Results from topical hydrocortisone therapy are particularly pleasing in chronic eczematous otitis externa and especially when it is combined with an antibiotic drug. Results are excellent also in nuchal eczema, dermatitis of the eyelids and in pruritus ani. More often than not, hydrocortisone ointment and lotions benefit more than do other standard remedies such diseases as atopic eczema, contact dermatitis, lichen simplex-chronicus and eczematized phases of conditions such as psoriasis and superficial mycotic infections. Preparations containing a combination of hydrocortisone and an antibiotic are more useful than hydrocortisone alone. When used with discrimination, with full attention to the selection of cases and proper concentration in the correct vehicle, hydrocortisone preparations in combination with antibiotics are excellent antieczematous agents.     

Identification of atypical strains of Malassezia spp. from cattle and dog

Yeast species in the genus Malassezia are lipophilic with the exception of Malassezia pachydermatis. During a study of the occurrence of Malassezia species in the external ear of 964 cattle and 6 dogs in Minas Gerais, Brazil, six lipid-dependent isolates could not be identified to known species. Four isolates came from healthy cows, one from a cow with otitis, and one from a healthy dog. When tested with Tweens and Cremophor EL as single sources of lipids, the strains grew on all sources except Cremophor EL. None of the six strains hydrolyzed esculin, and all produced catalase. Pigment production from tryptophan was variable. Partial large subunit rRNA sequences were obtained for two isolates that remained viable in culture. The strain from the cow with otitis was identified as a lipid-dependent variant of M. pachydermatis, and the strain from the dog was an atypical variant of Malassezia furfur.     

Malassezia Baillon, emerging clinical yeasts

The human and animal pathogenic yeast genus Malassezia has received considerable attention in recent years from dermatologists, other clinicians, veterinarians and mycologists. Some points highlighted in this review include recent advances in the technological developments related to detection, identification, and classification of Malassezia species. The clinical association of Malassezia species with a number of mammalian dermatological diseases including dandruff, seborrhoeic dermatitis, pityriasis versicolor, psoriasis, folliculitis and otitis is also discussed.     

Skin diseases associated with Malassezia species in humans. Clinical features and diagnostic criteria

Malassezia yeasts not only cause the well known pityriasis versicolor and folliculitis, but also play an important role in other skin diseases, including seborrheic dermatitis and atopic dermatitis. The presence of Malassezia yeasts may be confirmed by direct microscopic examination and cultures of skin scrapings. In pityriasis versicolor the direct microscopic examination is the rapidest and surest test for confirming the clinical diagnosis. The preparation will show a cluster of globose budding spores with thick or double wall and short hyphae. For detecting Malassezia in the other diseases the cultures is preferable. Culture is useful both for confirming the clinical diagnosis and for epidemiological investigations. The identification of the Malassezia species is not easy. The microscopic observation of the colony direct towards the identification of Malassezia species, but it is not enough to identify the colonies definitely. Several biochemical tests are necessary for a precise identification, such as catalase reaction, growth on media without lipid sources, ability to utilize hydrophilic emulsifiers as sole lipid source, esculin test, tryptophan test.     

A survey of 120 isolates of Malassezia (Pityrosporum) pachydermatis

The morphological, cultural and biochemical characteristics of 120 isolates of Malassezia (Pityrosporum) pachydermatis, isolated from chronic otitis externa in the dog, are discussed.     

Biotyping of Malassezia pachydermatis strains using the killer system

The killer phenomenon has been used as epidemiological marker for Candida albicans, where hundreds of biotypes can be obtained. The objective of this study is to observe the behaviour of 30 strains of Malassezia pachydermatis isolated from dogs with otitis (15) or dermatitis (15) against 9 killer yeasts, which, when grouped in triplets produced a 3 digit code (biotype). The growth inhibition of the 30 strains of M. pachydermatis due to the effect of the killer yeasts used permitted the determination of the following biotypes: 888 (33.3%), 212 (26.7%), 111 (16.7%), 312 (6.7%), 512 (6.7%), 242 (3.3%), 311 (3.3%) and 411 (3.3%). Biotypes 888, 212 and 111 occurred most frequently in both ear canal and skin samples.     

Taxonomy of Malassezia furfur: state of the art

Malassezia furfur is a lipophilic yeast considered as a normal component of the human skin flora. Apart from pityriasis versicolor, M. furfur has been linked to several skin diseases such as seborrheic dermatitis, folliculitis or atopic dermatitis. Moreover, these yeasts have been reported as agent of invasive human diseases including pneumonia, catheter-associated sepsis and peritonitis. The existence of morphological, serological, metabolical, biochemical and karyotipical differences has been described among isolates of these yeasts. These observations gave arguments for a possible intraspecific division, and this hypothesis has been confirmed by the existence of six species within the formerly called M. furfur (lipid-dependent Malassezia strains): M. furfur, Malassezia sympodialis, Malassezia globosa, Malassezia obtusa, Malassezia restricta and Malassezia slooffiae.     

A survey of mycotic otitis externa of dogs in Lisbon

One hundred and thirteen dogs of different breeds and with different clinical forms of external otitis were mycologically and bacteriologically examined. Forty six of those dogs showed abnormal cerumen with a high yeasts contamination. These yeasts belong to four species: Malassezia pachydermatis (80.4%), Cryptococcus laurentii (13.1%), Candida parapsilosis (4.3%) and Trichosporon cutaneum (2.1%). All strains, excepting C. laurentii were highly lipolytic. Most of the clinical cases associated with those yeasts were chronic, with hyperkeratosis and lichenification, and most of them were relapsed otitis (91.3%). The most affected dogs were a pendulous ears breeding (65.7%) and males (86.8%). Some dogs had other cutaneous disorders (seborrhoeic dermatitis, pemphigus). In vitro tests, using seven different antifungal drugs were systematically performed. All strains revealed to be 5-fluorocytosine-resistant and 32% of them were also resistant to nystatin. One M. pachydermatis isolated was resistant to all of the tested antifungal drugs.     

Producción de fosfolipasa y proteinasa en cepas de Malassezia pachydermatis aisladas de perros con otitis y sin otitis

BackgroundMalassezia pachydermatis is part of the skin microbiota of dogs and cats. M. pachydermatis has been associated with external otitis and seborrhoeic dermatitis, reported more often in dogs than in cats. When the physical, chemical or immunological mechanisms of the skin are altered, M. pachydermatis could act as a pathogen. Thus, several virulence factors, such as the ability to produce esterase, lipase, lipoxygenase, protease, chondroitin sulphatase, and hyaluronidase, have been studied.AimsIn the present study, we aim to identify the phospholipase activity measured at pH 6.3, and the proteinase activity measured at pH 6.3 and pH 6.8 (pH from ears of dogs with external otitis) of M. pachydermatis strains isolated from dogs with and without external otitis.MethodsThe phospholipase activity was measured using a semi-quantitative method with egg yolk, and the proteinase activity with a semi-quantitative method using bovine serum albumin agar. The study was performed on 96 isolates of M. pachydermatis, 43 isolated from dogs without clinical symptoms of otitis, and 52 isolated from dogs with otitis.ResultsIn our study, 75.8% of the isolates showed phospholipase activity at pH 6.3, and 81 and 97.9% of them showed proteinase activity measured at pH 6.3 and 6.8, respectively. A higher phospholipase activity was detected in strains isolated from dogs with otitis. The proteinase activity was increased at a pH of 6.8 (97.9%) in comparison to a pH of 6.3 (81%).ConclusionsOur results suggest that the phospholipase activity may play an important role in the invasion of host tissues in chronic canine otitis cases. The proteinase activity results obtained in this study suggest that a reduction in the pH of the treatment may improve its efficacy in the resolution of M. pachydermatis otitis.     

Uncommon cases of pityriasis versicolor

Malassezia may play a role in several dermatoses. It is responsible for foliculitis and mainly for pityriasis versicolor. Pityriasis versicolor is the most known dermatitis because of its clinical aspects and frequently for its poor response to the therapy, mainly in chronic forms. The clinical aspects of uncommon and rare forms of pityriasis versicolor have been reported. The data related to the patients observed in the last thirty years in Siena are reported. In addition, a study was carried out in Pisa by Professor F. Mancianti to identify species of Malassezia isolated in 37 patients.     

Recent developments in the immunology and biology of Malassezia species

Malassezia spp. are members of the normal cutaneous flora, but are also associated with several cutaneous diseases. Recent studies of the interaction of Malassezia spp. with melanocytes, fibroblasts, keratinocytes and dendritic cells have highlighted their potential to modulate the immune response directed against them. In normal skin they may downregulate the inflammatory response, allowing them to live as commensals. In contrast, in atopic/eczema dermatitis syndrome and psoriasis, they may elicit an inflammatory response that contributes to the maintenance of lesions. Future research may define ways to influence this inflammatory cycle and hence to control or prevent exacerbations of these diseases.     

Invasive external otitis: review of 12 cases.

Invasive external otitis is an infection caused by Pseudomonas aeruginosa that often occurs in elderly people with diabetes. Twelve cases that illustrate the problems associated with the clinical recognition and successful outcome of the condition were reviewed. The patients'' average age was 62.5 years, and they had been ill for an average of 1.8 months before admission to hospital. Predisposing factors included diabetes, swimming in a warm climate and the use of a hearing aid. Radionuclide bone scanning and surgical exploration revealed pathognomonic findings. Initial therapy was often suboptimal: one or more relapses occurred in seven of the patients. All of the patients were cured without relapse after a minimum of 4 weeks of therapy with tobramycin plus an anti-Pseudomonas penicillin. The average duration of the illness was 3.9 months. The outcome in invasive external otitis should be excellent if the condition is diagnosed early and appropriate therapy is instituted.     

化脓性中耳炎病原菌感染的研究进展

化脓性中耳炎是耳鼻喉科临床常见疾病,可导致听力下降、鼓膜充血、鼓膜穿孔、耳鸣、耳痛及流脓等。化脓性中耳炎主要由微生物进入中耳引起感染,使中耳黏膜发生化脓性病变,且不同患者感染的病原菌不同。本文从化脓性中耳炎的发病机制、病原菌及其耐药性和治疗方法等几个方面进行综述,以期为临床化脓性中耳炎的诊断及合理用药提供参考。     

Bilateral otitis media and hearing loss in an adult

Bilateral otitis media, an uncommon entity in adults, may represent the initial manifestation of a life-threatening systemic disease. Prompt recognition and treatment of the underlying disease is needed to preserve auditory function and prevent involvement of other organ systems. We present the case of a thirty-four-year-old male with bilateral serous otitis media and progressive hearing loss, which was refractory to antimicrobial therapy and middle ear drainage. A mastoid biopsy revealed necrotizing granulomatous inflammation. The differential diagnosis and probable cause of this unusual finding are discussed.     

Old drugs,new tricks: Emerging role of drug repurposing in the management of atopic dermatitis

Atopic dermatitis is a chronic recurring pruritic inflammatory skin disease manifested by increased pro-inflammatory mediators which lead to dry, thickened, cracked, scaly skin. The current treatment options for atopic dermatitis management comprise drawbacks and leave unmet effective clinical needs. So, the approach for repurposing existing drugs for atopic dermatitis management may potentially overcome these unmet needs. Diseases that share the common pathophysiological pathways with atopic dermatitis can serve as a foundation for the repurposing of drugs. Drugs used in the management of cancer, rheumatoid arthritis, and other immune-mediated diseases such as psoriasis are under investigation to know the potential in atopic dermatitis management by utilizing repurposing strategies for a novel therapeutic indication. This review mainly envisages the probable repurposing of drugs for the management of atopic dermatitis disease; the barriers and regulatory aspects involved in the repurposing of existing drugs.     

儿童腺样体肥大程度与分泌性中耳炎发生的相关性研究(英文)

目的:探讨儿童腺样体肥大程度与分泌性中耳炎发生及预后的相关性,指导临床医师对分泌性中耳炎作出早期诊断和治疗。方法:239例住院手术切除腺样体的儿童,常规行鼻咽侧位片、声导抗检查;部分伴耳部症状、声导抗显示C型曲线或查体可疑鼓室积液征者行颞骨CT检查或术中行鼓室穿刺。经统计学分析,比较分泌性中耳炎与腺样体肥大程度及咽鼓管咽口情况的相关性。结果:在239例腺样体肥大儿童中,经鼓室穿刺证实合并分泌性中耳炎者34例(63耳,14.2%),其中鼓室曲线呈B型者33耳(52.4%),C型(-200 dapa)者10耳(15.9%),C型(-200 dapa)者20耳(31.7%)。结果表明分泌性中耳炎的发生与腺样体肥大程度及咽鼓管园枕受压迫的程度呈正相关。结论:声导抗检查不能作为分泌性中耳炎诊断的金标准,必要时可行颞骨CT明确诊断;对腺样体肥大伴分泌性中耳炎的儿童鼻内镜下腺样体切除为其主要疗法,配合鼓室穿刺多可治愈,对反复发作的分泌性中耳炎行鼓室置管术,避免术后并发症的发生。     

Potential therapeutic effect of yeast killer toxin

Experimental infections were produced in guinea pigs, rabbits and dogs with lesions similar to those seen in human seborrheic dermatitis and otitis externa by cutaneous application of cultures of Malassezia furfur and M. pachydermatis. Infected animals were treated by topical application of a concentrated yeast killer toxin (Hansenula anomala UCSC 25F). Clinical recovery as well as negative mycological test cultures of infected animals proved to the clearly associated with the treatment by the killer toxin.     

Policies on antibiotics of south east London general practitioners for managing acute otitis media in children.

Questionnaires on antibiotic treatment of acute otitis media in children were sent to the general practitioners who make regular referrals to clinics in the King''s College Hospital group. The most popular first choice of drug was amoxycillin (44%), but 37% of general practitioners said that they often used oral phenoxymethylpenicillin. This drug has relatively low activity against Haemophilus influenzae and many strains of Staphylococcus aureus. It is poorly absorbed from the stomach, does not penetrate the middle ear well, and its use may be one factor in the development of chronic middle ear effusions after acute otitis media. Sixty two per cent of the doctors who replied never treated acute otitis media with intramuscular antibiotics, but 57% used oral loading doses. Ninety seven per cent never treated their patients without antibiotics.