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

Abstract

TABLE OF CONTENTS Introduction 4 History and taxonomy of the genus Malassezia 5 Biological characteristics of Malassezia organisms 5 Structure 5 Reproduction 6 Biochemistry 6 Distribution of Malassezia organisms on the host 6 Immunological and epidermal responses to Malassezia organisms 7 The immune response to Malassezia organisms 7 Antigen release, penetration and presentation 8 Cell‐mediated immune responses 8 IgG, IgM and IgA responses to Malassezia organisms 9 IgE responses to Malassezia organisms 10 Mast cell responses 11 Epidermal responses associated with Malassezia dermatitis 12 Malassezia organisms as pathogens in humans and animals 13 Diseases associated with Malassezia spp. in humans 13 Pityriasis versicolor 13 Malassezia folliculitis 13 Seborrheic dermatitis and dandruff 14 Atopic dermatitis 14 Malassezia fungaemia 14 Diseases associated with Malassezia spp. in animals 15 Malassezia dermatitis in dogs 15 Predisposing factors for overgrowth of Malassezia pachydermatis 15 Pathogenesis 16 Clinical features 16 Diagnosis 17 Treatment 18 Conclusions 19 References 19

Malassezia Species Associated With Dermatitis in Dogs and Their Antifungal Susceptibility

“…They reproduce asexually by budding from a broad base (Chen and Hill, 2005). The cell wall of Malassezia is very thick (0.12µm) and multilayered, consisting mainly of sugars (70%), lipids (15-20%) and proteins (10%) (Ashbee and Evans, 2002).…”

Antimycotic Activity of Some Aromatic Plants Essential Oils Against Canine Isolates of Malassezia pachydermatis: An in vitro Assay

“…The factors involved in the transition from commensalism to parasitism by M. pachydermatis in dogs are not fully understood even if it is well stated that the interface between commensalism and pathogenicity in Malassezia infections is a fine balance, in which both the regulation of host immune response and the activity of the fungus are strictly involved [7].…”

Comparative Analysis of Protein Profiles of Malassezia Pachydermatis Strains Isolated from Healthy Dogs and Dogs with Otitis Externa

“…In the study, the selected proteins of similar molecular weight could also correspond to antigens isolated by other authors: proteins characteristic only for strains derived from dogs with signs of otitis externa (61, 52, 36 kDa) can be the equivalent of some allergens identified by Chen and Hill (10) and Bond and Lloyd (7), and proteins detected in more than 90% of tested strains (55 and 48 kDa) can reproduce allergens recognised by sera of both healthy and atopic dogs (7). Profiles of protein antigens from M. pachydermatis strains obtained by different research groups are quite similar, despite small differences in the molecular weight of individual allergens, especially when considering the differences in the accuracy of the various methods of determination of molecular weights of proteins, different periods of culture, or different host immune system activity (7,10,15,25). Recent studies have shown that some of extracted proteins can possibly correspond to molecular weights of allergens (61, 52, 36 kDa); however, M. pachydermatis can also produce antigens undetectable by immunoblotting methods, as well as by stimulating cell-mediated response (11,22).…”

“…As a result of weakening of host defence mechanisms, or due to the changes in cutaneous microenvironment, the microorganism may undergo conversion into a pathogenic form (10). M. pachydermatis is responsible for about 30%-80% of cases of otitis externa and is associated with 30% of cases of seborrhoeic or atopic dermatitis in dogs (19).…”