Malassezia

Malassezia (formerly known as Pityrosporum) is a genus of related fungi, classified as yeasts, naturally found on the skin surfaces of many animals and humans.

Changes in nomenclature

Unfortunately, confusion exists about the recent information on Malassezia yeast species due to a series of changes in their nomenclature. Malassezia were originally identified by the French scientist Malassez in the late 19th century, hence their proper current name. In the mid 20th century they were reclassified into two species: Pityrosporum ovale which is lipid dependent and found only on humans, and Pityrosporum pachydermatis, which is lipophyllic but not lipid dependent and found on the skin of most animals. P. ovale was later divied into two classes, P. ovale and P. orbiculare, and later renamed again as Malassezia furfur. Work on these yeasts was complicated because they are extremely difficult to propogate in laboratory culture.

Later, in the mid 1990s, scientists at the Pasteur Institute in Paris, France (Evelyn Gueho and Jacques Guillot) discovered that there were indeed multiple species and correctly reclassified and named the genus as Malassezia with several distinct species. Currently there are 10 recognized species: globosa, restricta, furfur, slooffiae, symposialis, nana, yamatoensis, dermatis, obtusa, and pachydermatis.

Role in human diseases

Recently, identification of Malassezia on skin has been aided by the application of molecular or DNA based techniques very similar to those used by forensic scientists to identify criminal suspects. These investigations show that in humans the species causing most skin disease, including the most common cause of dandruff and seborrhoeic dermatitis is M. globosa. The skin rash of tinea versicolor (pityriasis versicolor) is also due to infection by this fungi.

As the fungus requires fat to grow, it is most common in areas with many sebaceous glands: on the scalp, face, and upper part of the body. When the fungus grows too rapidly, the natural renewal of cells is disturbed and dandruff appears with itching (a similar process may also occur with other fungi or bacteria).

References

http://cmr.asm.org/cgi/content/full/15/1/21?view=long&pmid=11781265, Ashbee H, Evans E, Immunology of diseases associated with Malassezia species, Clin Microbiol Rev, Vol. 15, No. 1, pp. 21-57, 2002, No. PMID 11781265.
Batra R, Boekhout T, Guého E, Cabañes F, Dawson T, Gupta A, Malassezia Baillon, emerging clinical yeasts, FEMS Yeast Res, Vol. 5, No. 12, pp. 1101-13, 2005, No. PMID 16084129.
http://jcm.asm.org/cgi/content/full/40/9/3350?view=long&pmid=12202578, Gemmer C, DeAngelis Y, Theelen B, Boekhout T, Dawson Jr T, Fast, noninvasive method for molecular detection and differentiation of Malassezia yeast species on human skin and application of the method to dandruff microbiology, J Clin Microbiol, Vol. 40, No. 9, pp. 3350-7, 2002, No. PMID 12202578.
Guého E, Midgley G, Guillot J, The genus Malassezia with description of four new species, Antonie Van Leeuwenhoek, Vol. 69, No. 4, pp. 337-55, 1996, No. PMID 8836432.
Gupta A, Batra R, Bluhm R, Boekhout T, Dawson T, Skin diseases associated with Malassezia species, J Am Acad Dermatol, Vol. 51, No. 5, pp. 785-98, 2004, No. PMID 15523360.
Gupta A, Kohli Y, Faergemann J, Summerbell R, Epidemiology of Malassezia yeasts associated with pityriasis versicolor in Ontario, Canada, Med Mycol, Vol. 39, No. 2, pp. 199-206, 2001, No. PMID 11346269.
Gupta A, Kohli Y, Summerbell R, Faergemann J, Quantitative culture of Malassezia species from different body sites of individuals with or without dermatoses, Med Mycol, Vol. 39, No. 3, pp. 243-51, 2001, No. PMID 11446527.
Nakabayashi A, Sei Y, Guillot J, Identification of Malassezia species isolated from patients with seborrhoeic dermatitis, atopic dermatitis, pityriasis versicolor and normal subjects, Med Mycol, Vol. 38, No. 5, pp. 337-41, 2000, No. PMID 11092380.
Nell A, James S, Bond C, Hunt B, Herrtage M, Identification and distribution of a novel Malassezia species yeast on normal equine skin, Vet Rec, Vol. 150, No. 13, pp. 395-8, 2002, No. PMID 11999275.
http://jcm.asm.org/cgi/content/full/40/4/1363?view=long&pmid=11923357, Sugita T, Takashima M, Shinoda T, Suto H, Unno T, Tsuboi R, Ogawa H, Nishikawa A, New yeast species, Malassezia dermatis, isolated from patients with atopic dermatitis, J Clin Microbiol, Vol. 40, No. 4, pp. 1363-7, 2002, No. PMID 11923357. </div>

External links

The actual descriptive text portion of the article above (and its Contents menu) are licensed under the GNU Free Documentation License then in effect published by the Free Software Foundation. The text article uses material from http://en.wikipedia.org/wiki/Malassezia (retrieval date: 2007-05-27) and is provided "as-is" and without warranty. Permission is granted to copy, distribute and/or modify only the actual descriptive text portion of the article above (and its Contents Box) under the GNU Free Documentation License. A copy of the license is available at: http://en.wikipedia.org/wiki/Wikipedia:Text_of_the_GNU_Free_Documentation_License. Any advertisements (or active links not embedded in the actual article) and the layout or selection thereof are excluded from such license.
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