Malassezia (formerly known as Pityrosporum) is a genus of related fungi, classified as yeasts, naturally found on the skin surfaces of many animals including humans. It can cause hypopigmentation on the trunk and other locations in humans if it becomes an opportunistic infection.
Some confusion exists about the naming and classification of Malassezia yeast species due to a series of changes in their nomenclature. Work on these yeasts has been complicated because they are extremely difficult to propagate in laboratory culture.
Malassezia were originally identified by the French scientist Louis-Charles Malassez in the late 19th century.Raymond Sabouraud identified a dandruff-causing organism in 1904 and called it "Pityrosporum malassez", honoring Malassez, but at the species level not at the genus level. When it was determined that the organisms were the same, the term "Malassezia" was judged to possess priority.[1]
In the mid-20th century, it was reclassified into two species:
- Pityrosporum (Malassezia) ovale, which is lipid-dependent and found only on humans. P. ovale was later divided into two species, P. ovale and P. orbiculare, but current sources consider these terms to refer to a single species of fungus, with M. furfur the preferred name.[2]
- Pityrosporum (Malassezia) pachydermatis, which is lipophilic but not lipid-dependent and found on the skin of most animals.
In the mid-1990s, scientists at the Pasteur Institute in Paris, France discovered additional species.[3]
Currently there are 10 recognized species:
- M. furfur
- M. pachydermatis[4]
- M. globosa[5]
- M. restricta[6]
- M. slooffiae[7]
- M. sympodialis[8]
- M. nana[9]
- M. yamatoensis[10]
- M. dermatis[11]
- M. obtusa
Gupta AK, Nicol K, Batra R.
American Journal of Clinical Dermatology - 2004;5(6):417-22. Review.Seborrheic dermatitis is a superficial fungal disease of the skin, occurring in areas rich in sebaceous glands. It is thought that an association exists between Malassezia yeasts and seborrheic dermatitis. This may, in part, be due to an abnormal or inflammatory immune response to these yeasts. The azoles represent the largest class of antifungals used in the treatment of this disease to date. In addition to their antifungal properties, some azoles, including bifonazole, itraconazole, and ketoconazole, have demonstrated anti-inflammatory activity, which may be beneficial in alleviating symptoms. Other topical antifungal agents, such as the allylamines (terbinafine), benzylamines (butenafine), hydroxypyridones (ciclopirox), and immunomodulators (pimecrolimus and tacrolimus), have also been effective. In addition, recent studies have revealed that tea tree oil (Melaleuca oil), honey, and cinnamic acid have antifungal activity against Malassezia species, which may be of benefit in the treatment of seborrheic dermatitis. In cases where seborrheic dermatitis is widespread, the use of an oral therapy, such as ketoconazole, itraconazole, and terbinafine, may be preferred. Essentially, antifungal therapy reduces the number of yeasts on the skin, leading to an improvement in seborrheic dermatitis. With a wide availability of preparations, including creams, shampoos, and oral formulations, antifungal agents are safe and effective in the treatment of seborrheic dermatitis.
Antifungal effect of Australian tea tree oil on Malassezia pachydermatis isolated from canines suffering from cutaneous skin disease.
Weseler A, Geiss HK, Saller R, Reichling J.
Schweiz Arch Tierheilkd. 2002 May;144(5):215-21.
The lipophilic yeast Malassezia pachydermatis is part of the normal skin flora of most warm-blooded organisms. In a number of surveys it could be demonstrated that this yeast species might be involved in different skin diseases like seborrhoeic dermatitis, especially in dogs and cats. In order to look for an alternative therapeutic agent to the commonly used antimycotic and antiseptic synthetic substances the in vitro activity of Australian tea tree oil, the essential oil of Melaleuca alternifolia, against several strains of Malassezia pachydermatis was examined. All tested strains showed remarkably high susceptibility to tea tree oil. With these results the excellent antibacterial activity of tea tree oil is extended to a new group of fungal pathogens colonizing mainly mammals' skin. During the last ten years there was an increasing popularity of tea tree oil containing human health care products. The presented data open up new horizons for this essential oil as a promising alternative agent for topical use in veterinary medicine as well.
In vitro activities of ketoconazole, econazole, miconazole, and Melaleuca alternifolia (tea tree) oil against Malassezia species.
Hammer KA, Carson CF, Riley TV.
Antimicrob Agents and Chemotherapy - 2000 Feb;44(2):467-9.
The in vitro activities of ketoconazole, econazole, miconazole, and tea tree oil against 54 Malassezia isolates were determined by agar and broth dilution methods. Ketoconazole was more active than both econazole and miconazole, which showed very similar activities. M. furfur was the least susceptible species. M. sympodialis, M. slooffiae, M. globosa, and M. obtusa showed similar susceptibilities to the four agents.
In vitro susceptibility of Malassezia furfur to the essential oil of Melaleuca alternifolia.
Hammer KA, Carson CF, Riley TV.
Journal of Medical and Veterinary Mycology - 1997 Sep-Oct;35(5):375-7.
The susceptibility of 64 Malassezia furfur isolates to Melaleuca alternifolia oil was determined. The minimum inhibitory concentration for 90% of isolates was 0.25% by agar dilution and 0.12% by broth dilution. These data indicate that tea tree oil may be useful in the treatment of skin conditions involving Malassezia furfur.
Antifungal activity of the essential oil of Melaleuca alternifolia (tea tree oil) against pathogenic fungi in vitro.
Nenoff P, Haustein UF, Brandt W.
Skin Pharmacology and Physiology - 1996;9(6):388-94.
The in vitro antifungal activity of tea oil, the essential oil of Melaleuca alternifolia, has been evaluated against 26 strains of various dermatophyte species, 54 yeasts, among them 32 strains of Candida albicans and other Candida sp. as well as 22 different Malassezia furfur strains. Minimum inhibitory concentrations (MIC) of tea tree oil were measured by agar dilution technique. Tea tree oil was found to be able to inhibit growth of all clinical fungal isolates. For the investigated dermatophytes MIC values from 1,112.5 to 4,450.0 micrograms/ml with a geometric mean of 1,431.5 micrograms/ml were demonstrated. Both C. albicans strains and the other strains belonging to the genus Candida and Trichosporon appeared to be slightly less susceptible to tea tree oil in vitro. However, their MIC values, which varied from 2,225.0 to 4,450.0 micrograms/ml (geometric mean 4,080 micrograms/ml), indicated moderate susceptibility to the essential oil of M. alternifolia. The lipophilic yeast M. furfur seemed to be most susceptible to tea tree oil. MIC values between 556.2 and 4,450.0 micrograms/ml (geometric mean 1,261.5 micrograms/ml) were found against the tested M. furfur strains. However, when calculated as percentage tea tree oil of the agar, the above-mentioned concentrations correspond to 0.5-0.44% tea tree oil content. These values are far below the usual relatively high therapeutic concentrations of the agent; approximately 5-10% solution or even the concentrated essential oil are used for external treatment. In comparison with tea tree oil, in vitro susceptibility against miconazole, an established topical antifungal, was tested. As expected, very low MIC values for miconazole were found for dermatophytes (geometric mean 0.2 microgram/ml), yeasts (geometric mean 1.0 microgram/ml), and M. furfur (geometric mean 2.34 micrograms/ml). It is suggested that the in vivo effect of tea tree oil ointment in the therapy of fungal infections of the skin and mucous membranes as well as in the treatment of dandruff, a mild form of seborrheic dermatitis, may be at least partly due to an antifungal activity of tea tree oil.
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