Good descriptions of Malassezia
Excellent, Clear Article:
http://flash.lymenet.org/scripts/ultimatebb.cgi?ubb=get_topic;f=1;t=130660;p=0
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https://www.sciencedirect.com/topics/medicine-and-dentistry/malassezia
Malassezia yeasts play a pathogenic role in pityriasis versicolor, Malassezia folliculitis, seborrheic dermatitis and dandruff, but have also been implicated in atopic dermatitis, psoriasis, and several other skin diseases. Rarely, they can cause severe systemic infections in premature neonates and immunosuppressed patients.
Malassezia is a dimorphic lipophilic yeast of the genus Malassezia, which colonizes the stratum corneum and forms part of the commensal flora of the skin.68
From: Clinical Mycology (Second Edition), 2009
Diseases Caused by Malassezia Species in Human Beings
M. Dolenc-Voljč, in The Microbiology of Skin, Soft Tissue, Bone and Joint Infections, 2017
Abstract
Malassezia yeasts are members of normal cutaneous microflora in humans and many domestic and wild animals. As lipophilic fungi, they colonize skin rich in sebaceous glands. They are considered opportunistic pathogens that may cause, under favorable circumstances, various skin diseases. Recent molecular techniques have resulted in the revision of the genus Malassezia. Fourteen different species have been recognized so far. Malassezia globosa, Malassezia restricta and Malassezia furfur are the most common species responsible for skin diseases in humans.
The interaction of Malassezia yeasts with the skin is complex and involves inflammatory, immunological and metabolic pathways. Malassezia yeasts play a pathogenic role in pityriasis versicolor, Malassezia folliculitis, seborrheic dermatitis and dandruff, but have also been implicated in atopic dermatitis, psoriasis, and several other skin diseases. Rarely, they can cause severe systemic infections in premature neonates and immunosuppressed patients. Treatment of Malassezia-related diseases is usually effective using topical or systemic azole antifungal drugs.
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Abstracts of articles on malessezia; Most of these articles relate to dogs and cats, but I've clipped some general statements.
https://www.ncbi.nlm.nih.gov/pubmed
The pathogenesis of Malassezia yeasts.
Cafarchia C, Otranto D.
Abstract
The genus Malassezia includes twelve species of yeast, many of which have been mainly associated with human and canine diseases. Malassezia pachydermatis colonizes the skin and mucosal sites of healthy dogs and cats. Despite being part of the normal cutaneous microflora, Malassezia spp. yeast may become pathogenic under certain circumstances. This article reviews the factors related to both host and yeast which affect the pathogenical or commensal phenotypes of Malassezia yeasts.
PMID: 18693560
[Indexed for MEDLINE]
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Abstract
Mycopathologia. 2005 Sep;160(2):143-9.
Occurrence and population size of Malassezia spp. in the external ear canal of dogs and cats both healthy and with otitis.
Cafarchia C, Gallo S, Capelli G, Otranto D.
Abstract
Malassezia yeasts are commensal organisms of human and animal skin that occasionally act as pathogens; lipid-dependent species are associated with human skin disorders. [...] (The rest of the abstract discusses the studies related to malassezia in the ears of dogs and cats).
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Mol Cell Probes. 2007 Jun;21(3):229-38. Epub 2007 Jan 23.
Molecular characterization of Malassezia isolates from dogs using three distinct genetic markers in nuclear DNA.
Cafarchia C, Stefania Latrofa M, Testini G, Parisi A, Guillot J, Gasser RB, Otranto D.
Abstract
Little precise information is available on the systematics, genetics, ecology and epidemiology of yeasts of the genus Malassezia from different animal species. [Animal-related studies; rest of abstract describes specific DNA studies.]
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Abstract
Mol Cell Probes. 2011 Feb;25(1):1-7. doi: 10.1016/j.mcp.2010.12.003. Epub 2010 Dec 28.
Advances in the identification of Malassezia.
Cafarchia C, Gasser RB, Figueredo LA, Latrofa MS, Otranto D.
Abstract
Members of the genus Malassezia are lypophilic and/or lipid-dependent, unipolar budding yeasts that can become pathogenic under the influence of particular predisposing factors (e.g., changes in the cutaneous microenvironment and/or alterations in host defences). This genus comprises at least 14 species, which have been identified traditionally based on their morphology and biochemical features. However, phenetic characteristics often do not allow the identification or delineation of closely related Malassezia spp., such that molecular tools need to be used to assist in fundamental studies of the epidemiology and ecology of Malassezia as well as aspects of the pathogenesis and disease caused by members of this genus. This article briefly reviews the morphological and biochemical methods commonly used for the identification of Malassezia as well as DNA technological methods that have been established for the specific identification of members of this genus and the diagnosis of their infections. New avenues for the development of improved molecular-diagnostic methods to overcome diagnostic limitations and to underpin fundamental investigations of this interesting group of yeasts are proposed.
PMID: 21193026 DOI: 10.1016/j.mcp.2010.12.003
[Indexed for MEDLINE]
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Abstract
Br J Dermatol. 2014 Feb;170(2):332-41. doi: 10.1111/bjd.12680.
Efficient identification of Malassezia yeasts by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS).
Kolecka A, Khayhan K, Arabatzis M, Velegraki A, Kostrzewa M, Andersson A, Scheynius A, Cafarchia C, Iatta R, Montagna MT, Youngchim S, Cabañes FJ, Hoopman P, Kraak B, Groenewald M, Boekhout T.
Abstract
BACKGROUND:
Infections caused by Malassezia yeasts are most likely underdiagnosed, because fatty acid supplementation is needed for growth. Rapid identification of Malassezia species is essential for appropriate treatment of Malassezia-related skin infections, fungaemia and nosocomial outbreaks in neonates, children and adults and can be life-saving for those patients. Ma-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) has been reported to be a rapid and reliable diagnostic tool to identify clinically important yeasts, but so far no data have been reported on identification of Malassezia isolates with this technique.
[...]
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Abstract
Med Mycol. 2014 Apr;52(3):264-9. doi: 10.1093/mmy/myt004. Epub 2013 Dec 22.
Bloodstream infections by Malassezia and Candida species in critical care patients.
Iatta R, Cafarchia C, Cuna T, Montagna O, Laforgia N, Gentile O, Rizzo A, Boekhout T, Otranto D, Montagna MT.
Abstract
Despite being considered an emerging yeast related to immunocompromised individuals, severe infections by Malassezia furfur have not been evaluated.
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Malassezia Infections in Humans and Animals: Pathophysiology, Detection, and Treatment
Aristea Velegraki, Claudia Cafarchia, Georgios Gaitanis, Roberta Iatta, and Teun Boekhout*
Joseph Heitman, Editor
This article has been cited by other articles in PMC.
Introduction
The fungal genus Malassezia comprises lipid-dependent and lipophilic yeast species that are part of the normal skin microbiota. The 14 species are classified in class Malasseziomycetes in the Ustilaginomycotina of Basidiomycota. Malassezia species can be involved in skin disorders, such as pityriasis versicolor, seborrheic dermatitis, atopic eczema, and folliculitis, and occur at higher population densities on scalps with dandruff than on scalps without dandruff. Occasionally, invasive infections by Malassezia pachydermatis and lipid-dependent Malassezia spp. occur in neonates, most often in those who are receiving intravenous lipid supplementation, or in immunocompromised patients receiving parenteral nutrition via a catheter. Malassezia spp. have not yet been cultured from the environment, but metagenomics identified Malassezia
phylotypes from terrestrial and marine habitats. For instance, Malassezia ribosomal DNA (rDNA) has been reported from soil nematodes, sponges, and rocks. Undeniably, much remains to be discovered about the spectrum of habitats exploited by Malassezia that would advance our knowledge on the ecological relationships between the Malassezia skin biotic community, their hosts, and the environment. The aim of this article is to review and discuss the literature available on the pathogenesis, detection, typing, and treatment of Malassezia infections in humans and animals.
Pathophysiology on Human Skin
The pathophysiology of Malassezia-caused or Malassezia-exacerbated skin conditions is largely unknown, owing to the complex interactions of this commensal with the skin, an organ that has been on the edge of extreme selection pressure during evolution. In healthy skin, Malassezia
yeasts exploit essential nutrients for their growth without inflicting disease. When this process is perturbed, Malassezia yeasts adapt by modifying the expression of enzymes involved in the acquisition of energy, such as lipases and phospholipases, and at the same time synthesize an array of bioactive indoles that act through the aryl-hydrocarbon receptor (AhR), which is expressed on almost all cell types found in the epidermis.
melanogenesis, and probably inhibit antagonist microbes.
A major challenge would be to comprehend the multifaceted interactions of Malassezia yeasts with the human skin during health and disease. These include (a) commensalism (healthy skin), as there is no strong evidence for a mutualistic or beneficial relationship of the Malassezia microbiome and the skin; (b) subtle alterations in the function of skin melanocytes, resulting in hypo- or hyperpigmented plaques with characteristic clinical absence of inflammation and mild alterations in the epidermal barrier function (pityriasis versicolor); (c) inflammation without generation of antibody-mediated immunity (seborrheic dermatitis and dandruff); (d) induction of specific immunity (atopic dermatitis); and (e) invasion and inflammation of the hair follicle (Malassezia folliculitis). Interestingly, the high lipase activity of M. globosa from folliculitis specimens during the summer months may be promoted by sweat components, such as sodium chloride and lactic acid, thus laying a framework for examining potential metabolome, structure and function relationships between M. globosa lipases and the human skin. In seborrheic dermatitis and dandruff, there is a difference in the quality of sebum lipids between healthy and diseased skin, while the expression and function of Malassezia lipases in addition to barrier function defects and individual susceptibility take part in the exacerbation of these conditions. Recently, culture and biopsy evidence supported an association of M. restricta and M. globosa with rare nipple hyperkeratotic lesions in young women, who responded to a combination therapy of oral itraconazole and topical ketoconazole. This denotes that the metabolome of strains involved in rare presentations of skin diseases should be thoroughly investigated, clearly in conjunction with key host and environmental factors.
In that respect, at least two Malassezia yeast metabolic pathways, i.e., phospholipase production and indole pigment synthesis, have been associated with strains isolated from human and animal diseased skin. Malassezia produces potent indolic AhR ligands, such as indirubin and indolo [3,2-b] carbazole (ICZ), which potentially modify the function of almost all cells found in the epidermis and express this receptor. In view of the AhR participation in (a) carcinogenesis, (b) immune regulation, and (c) the mediation of ultraviolet radiation damage, a hypothesis on the potential contribution of Malassezia yeasts in skin carcinogenesis has been formulated.
Risk Factors for Malassezia Fungemia and Disseminated Disease
Patients under total parenteral nutrition (TPN) and immunocompromised patients with increased length of stay (LOS) in intensive care units are at risk for Malassezia infections. Risk for Malassezia infections is also high in very-low-birth-weight infants (<1500 abdominal="" access="" acid="" adherence="" administration="" after="" and="" antibiotics="" antifungal="" as="" biofilm="" bowel="" broad-spectrum="" by="" catheter="" catheters.="" central="" coinfection="" colonization.="" colonization="" comprising="" compromised="" condition="" conjunction="" contribute="" corresponding="" degree="" delayed="" diagnosis="" diseases="" dissemination="" dosing="" endotracheal="" enhanced="" enterocolitis="" exposure="" factors="" favour="" focal="" followed="" formation="" fungemia="" further="" g="" gastric="" highest="" horizontal.="" host="" iatrogenic="" immature="" immunity="" in="" including="" infant="" infants.="" infection="" inhibitors="" injury="" insufficient="" intubation="" invasive="" is="" lead="" malassezia="" may="" mechanism="" necrotizing="" nutrition="" occasionally="" of="" or="" p="" parenteral="" pathogen="" perforation="" persistent="" poor="" postnatal="" premature="" prematurity="" processes.="" prognosis.="" proliferation="" properties="" removal="" result="" s="" skin="" steroids="" subsequent="" such="" surgery="" that="" the="" these="" tissue="" to="" transmission="" treatments="" use="" valve="" vascular="" vertical="" virulence="" with="">
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