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AUREOBASIDIUM Mold Specie Picture

Aureobasidium is a known Type I and Type III allergen that can sometimes cause infections in the human skin, nails, and eyes. The U.S. Government's Occupational Safety and Health Administration [OSHA] lists both Aureobasidium and Aureobasidium pullulans as an allergen and irritant, and as a cause of Hypersensitivity pneumonitis and Dermatitis.

Aureobasidium pullulans


A. pullulans
showing chains of 1- to 2-celled, darkly pigmented arthroconidia representing the Scytalidium anamorph of Aureobasidium and the presence of numerous hyaline, single-celled, ovoid-shaped conidia (ameroconidia) which are produced on short denticles. For more aureobasidium mold picture, please visit or click on: Aureobasidium Mold Picture.

Colonies are fast growing, smooth, covered with slimy masses of conidia, cream or pink to brown or black. Hyphae are hyaline and septate, frequently becoming dark-brown with age and undergoing holothallic transformation to form chains of 1- to 2-celled, thick-walled, darkly pigmented arthroconidia commonly called chlamydoconidia. These arthroconidia actually represent the Scytalidium anamorph of Aureobasidium and are only of secondary importance in recognizing members of this genus. Conidia are produced synchronously in dense groups from indistinct scars or from short denticles on undifferentiated, hyaline to sub-hyaline hyphae. Conidia are hyaline, smooth-walled, single-celled (ameroconidia), ellipsoidal but of variable shape and size (8-12 x 4-6 um), often with an indistinct hilum (a mark or scar at the point of attachment). Temperature range for growth 2-35C; optimum 25C; maximum 35C (higher in some human pathogenic isolates).

This species has two varieties: A. pullulans var. pullulans, with a colony which remains pink, light brown, or yellow for at least three weeks, and A. pullulans var. melanogenum which soon becomes black or greenish-black due to dark hyphae which often fall apart into separate cells.

Descriptions and Habitats

Aureobasidium is a cosmopolitan, dematiaceous fungus commonly isolated from plant debris, soil, wood, textiles, and indoor air environment.  This yeast-like fungus is commonly found on caulk or damp window frames in bathrooms.  Aureobasidium (Pullularia) may be pink or black in color.  Although it seldom causes infections, it can be allergenic. This is one type of mold that is a type of mildew.  It will grow in cooler climates and along with Cladosporium is commonly found growing on siding.

Pullularia occurs indoors in areas of free water, such as condensate pans, or as a primary colonist of broadloom following a flood. Because its growth form is yeast-like (and are not forcibly discharged), its cells/spores only become airborne through mechanical disruption of contaminated materials or aspiration of contaminated water.

Aureobasidium pullulans is not a primary human pathogen nor is it recognized as a producer of significant mycotoxins. High airborne levels of this fungus have been associated with allergic complaints probably due to respiratory irritation mediated by cell-wall components (e.g. beta glucans, glycoproteins), it has also been known as an irritant, and to cause pulmonary problems (small airway).

Species

According to the mycological information provided in the website, www.doctorfungus.org, the genus Aureobasidium includes 14 species and one variety. Among these, Aureobasidium pullulans is the only well-known species.

Health Effects

Based on the research conducted by Mycology Online, it is reported that Aureobasidium pullulans has a world-wide distribution and it is usually isolated as a saprophyte, occasionally from skin and nails. However, it has also been reported as a rare causative agent of phaeohyphomycosis, mycotic keratitis and peritonitis in patients on continuous ambulatory peritoneal dialysis (CAPD). 

Aureobasidium is a known Type I and Type III allergen that can sometimes cause infections in the human skin, nails, and eyes. The U.S. Government's O.S.H.A. Agency lists both Aureobasidium and Aureobasidium pullulans as an allergen and irritant, and as a cause of Hypersensitivity pneumonitis and Dermatitis.

Aureobasidium pullulans growing in a mold culture plate after 7 days of growth.
  Aureobasidium pullulans growing in a mold culture plate [photo taken at 7 days of mold growth]. From Identifying Filamentous Fungi,
Guy St.-Germain & Richard Summerbell.

Macroscopic Features

It grows moderately rapidly and matures within 7 days of incubation. The colony diameter is 1 to 3 cm following incubation at 25C for 7 days on potato glucose agar. The colonies are flat, smooth, moist, yeast-like, mucoid to pasty, shiny and leathery in appearance. The surface is white, pale pink or yellow at the beginning and becomes brown to black and velvety with a grayish fringe by aging. Reverse is pale or black.

Microscopic Features

When the colony is young, moist, and yeast-like, unicellular budding yeast cells (blastoconidia) are the only structures observed microscopically. By aging, while the colony gets black and velvety, hyphae become visible.

Blastoconidia are pale in color. The synchronous development of blastoconidia in tufts is typical. Hyphae are septate. They appear hyaline at the beginning and get dark brown by aging. The width of the hyphae is generally 2-10 m but may be as thick as 15-20 m. Aureobasidium has no distinct conidiophores. Conidiogenous cells, which are not much differentiated, are either intercalary or located terminally in the hyphae. The conidia (4-6 x 2-3 m in size) are one-celled, hyaline and oval to cylindrical in shape. They form clusters or are located along the hyphae. These conidia continue to multiply by budding and form secondary blastoconidia.

As well as blastoconidia, chlamydoconidia and arthroconidia may also be observed. The hyphae of some strains differentiate to form thick-walled, large (up to 12x6 m in size), phaeoid (brown in color) chlamydoconidia. Thick-walled, one- to two-celled, phaeoid arthroconidia are produced in old, mature cultures.

Laboratory Precautions

No special precautions other than general laboratory precautions are required.

Susceptibility

No susceptibility data are available for Aureobasidium. In vitro susceptibility testing methods are not yet standardized for dematiceaous fungi.

The mycological information gathered and organized in this extensive research on different Pathogenic Molds was  sourced out from the list of informative websites below:

http://www.osha.gov | http://www.doctorfungus.org | http://www.mycology.adelaide.edu.au | http://www.mycology.net | http://www.dehs.umn.edu | http://www.mold-help.org | http://www.mycology.net | http://www.pfdb.net | http://www.clinical-mycology.com | http://www.botany.utoronto.ca | http://www.med.sc.edu | http://www.tigr.org | http://www.pangloss.ucsfmedicalcenter.org | http://www.dermnz.org | http://ncbi.nlm.nih.gov | http://www.wadsworth.org | http://botit.botany.wisc.edu

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