| Malassezia globosa | |
|---|---|
 | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Fungi |
| Division: | Basidiomycota |
| Class: | Malasseziomycetes |
| Order: | Malasseziales |
| Family: | Malasseziaceae |
| Genus: | Malassezia |
| Species: | M. globosa |
| Binomial name | |
| Malassezia globosa Midgley, E.Guého & J.Guillot | |
In 2007, it was discovered that the responsible agent is a scalp specific fungus, Malassezia globosa (previously thought to be Malassezia furfur ), that metabolizes triglycerides present in sebum by the expression of lipase, resulting in a lipid byproduct: oleic acid. [2]
Identification of Malassezia on skin has been aided by the application of molecular or DNA-based techniques. These investigations show that the Malassezia species causing most skin disease in humans, including the most common cause of dandruff and seborrhoeic dermatitis, is M. globosa (though M. restricta is also involved). [1] The skin rash of tinea versicolor (pityriasis versicolor) is also due to infection by this fungus.
As the fungus requires fat to grow, [3] it is most common in areas with many sebaceous glands: on the scalp, [4] 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).
A project in 2007 has sequenced the genome of dandruff-causing Malassezia globosa and found it to have 4,285 genes. [5] [6] M. globosa uses eight different types of lipase, along with three phospholipases, to break down the oils on the scalp. Any of these 11 proteins would be a suitable target for dandruff medications.
The number of specimens of M. globosa on a human head can be up to ten million. [4]
Malassezia globosa has been predicted to have the ability to reproduce sexually, [7] but this has not been observed.
Dandruff is a skin condition that mainly affects the scalp. Symptoms include flaking and sometimes mild itchiness. It can result in social or self-esteem problems. A more severe form of the condition, which includes inflammation of the skin, is known as seborrhoeic dermatitis.
Tinea versicolor is a condition characterized by a skin eruption on the trunk and proximal extremities. The majority of tinea versicolor is caused by the fungus Malassezia globosa, although Malassezia furfur is responsible for a small number of cases. These yeasts are normally found on the human skin and become troublesome only under certain circumstances, such as a warm and humid environment, although the exact conditions that cause initiation of the disease process are poorly understood.
Seborrhoeic dermatitis is a long-term skin disorder. Symptoms include flaky, scaly, greasy, and occasionally itchy and inflamed skin. Areas of the skin rich in oil-producing glands are often affected including the scalp, face, and chest. It can result in social or self-esteem problems. In babies, when the scalp is primarily involved, it is called cradle cap. Seborrhoeic dermatitis of the scalp may be described in lay terms as dandruff due to the dry, flaky character of the skin. However, as dandruff may refer to any dryness or scaling of the scalp, not all dandruff is seborrhoeic dermatitis. Seborrhoeic dermatitis is sometimes inaccurately referred to as seborrhoea.
Candida is a genus of yeasts. It is the most common cause of fungal infections worldwide and the largest genus of medically important yeast.
Malassezia is a genus of fungi. It is the sole genus in family Malasseziaceae, which is the only family in order Malasseziales, itself the single member of class Malasseziomycetes. Malassezia species are naturally found on the skin surfaces of many animals, including humans. In occasional opportunistic infections, some species can cause hypopigmentation or hyperpigmentation on the trunk and other locations in humans. Allergy tests for these fungi are available. It is believed French revolutionary Jean-Paul Marat suffered from a fungal infection from Malassezia restricta, which lead to his frequent bathing in a medicinal substance.
Tinea capitis is a cutaneous fungal infection (dermatophytosis) of the scalp. The disease is primarily caused by dermatophytes in the genera Trichophyton and Microsporum that invade the hair shaft. The clinical presentation is typically single or multiple patches of hair loss, sometimes with a 'black dot' pattern, that may be accompanied by inflammation, scaling, pustules, and itching. Uncommon in adults, tinea capitis is predominantly seen in pre-pubertal children, more often boys than girls.
Dermatophytosis, also known as ringworm, is a fungal infection of the skin (Dermatomycosis). Typically it results in a red, itchy, scaly, circular rash. Hair loss may occur in the area affected. Symptoms begin four to fourteen days after exposure. Multiple areas can be affected at a given time.
Selenium disulfide, also known as selenium sulfide, is a chemical compound and medication used to treat seborrheic dermatitis, dandruff, and pityriasis versicolor. It is applied to the affected area as a lotion or shampoo. Symptoms frequently return if treatment is stopped.
Malassezia furfur is a species of yeast that is naturally found on the skin surfaces of humans and some other mammals. It is associated with a variety of dermatological conditions caused by fungal infections, notably seborrhoeic dermatitis and tinea versicolor. As an opportunistic pathogen, it has further been associated with dandruff, malassezia folliculitis, pityriasis versicolor (alba), and malassezia intertrigo, as well as catheter-related fungemia and pneumonia in patients receiving hematopoietic transplants. The fungus can also affect animals, including dogs.
In biochemistry, lipase refers to a class of enzymes that catalyzes the hydrolysis of fats. Some lipases display broad substrate scope including esters of cholesterol, phospholipids, and of lipid-soluble vitamins and sphingomyelinases; however, these are usually treated separately from "conventional" lipases. Unlike esterases, which function in water, lipases "are activated only when adsorbed to an oil–water interface". Lipases perform essential roles in digestion, transport and processing of dietary lipids in most, if not all, organisms.
Malassezia folliculitis or Pityrosporum folliculitis, is a skin condition caused by infection by Malassezia yeast.
Climbazole is a topical antifungal agent commonly used in the treatment of human fungal skin infections such as dandruff, seborrhoeic dermatitis and eczema. Climbazole has shown a high in vitro and in vivo efficacy against Malassezia spp. that appear to play an important role in the pathogenesis of dandruff. Its chemical structure and properties are similar to other azole fungicides such as ketoconazole, clotrimazole and miconazole.
Microsporum canis is a pathogenic, asexual fungus in the phylum Ascomycota that infects the upper, dead layers of skin on domesticated cats, and occasionally dogs and humans. The species has a worldwide distribution.
Malassezia equina is a fungus first isolated in horses, which can cause opportunistic infections in animals. Its type strain is MA146=CBS 9969. This species will not grow without any lipid supplementation. It grows slowly and forms small colonies. In the lab, colonies will not grow at temperatures of 40 °C, differing from M. sympodialis-related species, such M. dermatis and M. nana, which can grow at this temperature. Malassezia caprae cells are ovoidal.
Malassezia caprae is a fungus first isolated in goats, which can cause opportunistic infections in animals. Its type strain is MA383=CBS 10434. This species will not grow without any lipid supplementation. It grows slowly and forms small colonies. In the lab, colonies will not grow at temperatures of 40 °C, differing from M. sympodialis-related species, such M. dermatis and M. nana, which can grow at this temperature. Malassezia caprae cells are ellipsoidal to more or less spherical.
Malassezia pachydermatis is a zoophilic yeast in the division Basidiomycota. It was first isolated in 1925 by Fred Weidman, and it was named pachydermatis after the original sample taken from an Indian rhinoceros with severe exfoliative dermatitis. Within the genus Malassezia, M. pachydermatis is most closely related to the species M. furfur. A commensal fungus, it can be found within the microflora of healthy mammals such as humans, cats and dogs, However, it is capable of acting as an opportunistic pathogen under special circumstances and has been seen to cause skin and ear infections, most often occurring in canines.
Malassezia sympodialis is a species in the genus Malassezia. It is characterized by a pronounced lipophily, unilateral, percurrent or sympodial budding and an irregular, corrugated cell wall ultrastructure. It is one of the most common species found on the skin of healthy and diseased individuals. It is considered to be part of the skin's normal human microbiota and begins to colonize the skin of humans shortly after birth. Malassezia sympodialis, often has a symbiotic or commensal relationship with its host, but it can act as a pathogen causing a number of different skin diseases, such as atopic dermatitis.
Malassezia arunalokei is a species of yeast-like fungus that was identified as a new to science in 2016. It has been isolated from the skin of both seborrheic dermatitis patients and healthy individuals from India. A combination of several phenotypic characteristics distinguish this species from others in genus Malassezia. These include: colony morphology ; the absence of activity from the enzyme catalase; growth at 37 °C (99 °F); and the precipitation that results when grown with the chemicals Tween 20 or Cremophor EL.