Mold Definitions

For a definition of specific mold types, click on the name below.

Note: In the definitions, "Aw" refers to the water activity measurement, where Aw is equal to the relative humidity of the air surrounding the sample when the air and the sample are at equilibrium (in an enclosed space).

For additional help in finding word definitions:
http://ppathw3.cals.cornell.edu/glossary/Glossary.htm "On-Line Glossary of Technical Terms in Plant Pathology", provided by Cornell University.

For additional information:
http://www.aerotechlabs.com/Infobase/resource.aspx?CatID=1 , "Microbial Glossary", provided by Aerotech Laboratories, Inc.

http://www.emlab.com/app/fungi/Fungi.po "An Index of Some Commonly Encountered Fungal Genera",provided by Environmental Microbiology Laboratory, Inc.

http://www.dehs.umn.edu/iaq/fungus/glossary.html , "Fungal Glossary", provided by the University of Minnesota Department of Environmental Health and Safety.

http://www.doctorfungus.org/thefungi/description_index.htm , "Fungi Descriptions", provided by the DoctorFungus Corporation.

http://www.mercksource.com/ (abbreviated URL), "Dorland's Medical Dictionary", provided by W. B. Saunders.

Absidia
A zygomycete fungus. Reported to be allergenic. May cause mucorosis in immune compromised individuals. The sites of infection are the lung, nasal sinus, brain, eye and skin. Infection may have multiple sites.

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Acremonium(Cephalosporium)
Reported to be allergenic. Can produce a trichothecene toxin that is toxic if ingested. It was the primary fungus identified in at least two houses where the occupant complaints were nausea, vomiting and diarrhea. Asexual state of Emericellopsis sp., Chaetomium sp., and Nectripsis sp. It can produce mycetomas, infections of the cornea and nails.

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Alternaria
Aw - 0.89. Conidia dimensions: 18-83 x 7-18 microns. A very common allergen with an IgE mediated response. It is often found in carpets, textiles and on horizontal surfaces in building interiors. Often found on window frames. Outdoors it may be isolated from samples of soil, seeds and plants. It is commonly found in outdoor samples. The large spore size, 20 - 200 microns in length and 7 - 18 microns in sizes, suggests that the spores from these fungi will be deposited in the nose, mouth and upper respiratory tract. It may be related to bakers' asthma. It has been associated with hypersensitivity pneumonitis. The species Alternaria alternata is capable of producing tenuazonic acid and other toxic metabolites that may be associated with disease in humans or animals. Common cause of extrinsic asthma (immediate-type hypersensitivity: type I). Acute symptoms include edema and bronchiospasms; chronic cases may develop pulmonary emphysema.

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Amerospore
A spherical or oval single-celled fungal spore that is practically unidentifiable by itself. Generawith this type of sporeinclude, but are not limited to, AspergillusPenicillium, and Trichoderma.
For example, Penicillium is easily identifiable when sampling using culturing techniques. However, when sampling with non-culturing techniques, such as spore traps or tape-lifts, the free spores with no remnants of the fungal structure are indistinguishable from Aspergillus and various other genera that also produce small round and oval spores with little or no pigmentation. Due to this fact, Penicillium will often be categorized on laboratory reports in an "amerospore" and/or "Aspergillus/Penicillium" group.

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Arthrinium
Widespread saprophyte found on decomposing plant material, particularly grasses, and on soil. It is a white, fuzzy mold. It should be considered to be an allergen. This fungus has also been documented in various subcutaneous infections. No diseases related to toxic effects have been recorded to date.

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Ascospore
A spore borne in a special cell called an ascus. Spores of this type are reported to be allergenic.
All ascomycetes, members of a group of fungi called Ascomycotina, have this type of spore. The minute black dots on rotting wood and leaves or the little cups on lichens are examples of ascomycetes; another is the "truffle" mushroom.

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Aspergillus caesiellus
This species is only occasionally pathogenic.

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Aspergillus candidus
Aw 0.75. Conidia dimensions: 2.5-4 microns. Found in warm soils, grain and in the secondary decay of vegetation. Associated with respiratory complaints in a recent house investigation. Can produce the toxin petulin that may be associated with disease in humans and other animals.

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Aspergillus carneus
This species is only occasionally pathogenic.

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Aspergillus clavatus
Conidia dimensions: 3-4.5 x 2.5-4.5 microns. Found in soils and animal manure.
Can produce the toxin petulin that may be associated with disease in humans and other animals. This species is only occasionally pathogenic.

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Aspergillus deflectus
This species is only occasionally pathogenic.

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Aspergillus flavus
Aw 0.78. Conidia dimensions: 3-6 microns or 3-5 microns. It grows on moldy corn and peanuts. It can be found in warm soil, foods and dairy products. Some strains are capable of producing a group of mycotoxins- in the aflatoxin group. Aflatoxins are known animal carcinogens. There is limited evidence to suggest that this toxin is a human carcinogen. The toxin is poisonous to humans by ingestion. It may also result in occupational disease via inhalation. Experiments have indicated that it is teratogenic and mutagenic. It is toxic to the liver. It is reported to be allergenic. Its presence is associated with reports of asthma. It can be found in water-damaged carpets. The production of the fungal toxin is dependent on the growth conditions and on the substrate used as a food source. This fungus is associated with aspergillosis of the lungs and/or disseminated aspergillosis. This fungus is occasionally identified as the cause of corneal, otomycotic and nasoorbital infections.

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Aspergillus fumigatus
Aw 0.82; Optimum> 0.97. Conidia dimensions: 2-3.5 microns. Considered a human pathogen, this organism causes both allergic aspergillosis and invasive aspergillosis (invasive aspergillosis usually affects individuals who are immune compromised). It is commonly found outdoors on cereal grains, in cool to warm soils, and in compost piles (even with temperatures exceeding 40 degrees C).

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Aspergillus glaucus
Conidia dimensions: 5-6.5 microns. Common outdoor fungus in the winter. It is reported to be allergenic. This species is only occasionally pathogenic. It can grow on leather. This fungus can grow at low moisture levels on grains, sugary food products, meat and wool. The ascomycetous state is Eurotium sp.

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Aspergillus nidulans
Aw 0.78. Conidia dimensions: 2-4 microns. Found in mild to warm soils and on slowly decaying plants. Can produce the mycotoxin sterigmatocystin. This toxin has been shown to produce liver and kidney damage in lab animals. This fungus is associated with aspergillosis of the lungs and/or disseminated aspergillosis. This species is only occasionally pathogenic.

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Aspergillus niger
Aw 0.77; Optimum> 0.97. Conidia dimensions: 3.5 - 5 microns or 4 to 5 microns. Less common cause of aspergillosis. It has a musty odor. It is commonly found in the environment on textiles, in soils, grains, fruits and vegetables. It has been reported to cause skin and pulmonary infections. It is a common cause of fungal related ear infections, including otomycosis.

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Aspergillus ochraceus
Aw 0.77. Conidia dimensions: 2.5 - 3 microns. Found in grains, soil and salted food products. It is not usually associated with decaying vegetation. Can produce a kidney toxin ochratoxin A that may produce ochratoxicosis in humans. This is also known as Balkan nephropathy. The toxin is produced at optimum growth conditions at 25 degrees C and high moisture conditions. The ochratoxin may also be produced by other Aspergillus sp. and Penicillium sp. Other toxins that can be produced by this fungus include penicillic acid, xanthomegnin and viomellein. These are all reported to be kidney and liver toxins.

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Aspergillus oryzae
This species is only occasionally pathogenic.

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Aspergillus parasiticus
Some strains are capable of producing a group of mycotoxins- in the aflatoxin group. Aflatoxins are known animal carcinogens. There is limited evidence to suggest that this toxin is a human carcinogen. The toxin is a poisonous to humans by ingestion. Experiments have indicated that it is teratogenic and mutagenic. It is toxic to the liver. The production of the fungal toxin is dependent on the growth conditions and on the substrate used as a food source.

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Aspergillus/Penicillium-Like
This category is included on laboratory analysis reports for air samples containing certain free spores without other identifying structures.The free spores of Aspergillus and Penicillium (and other genera with small, round or ovoid, and colorless spores) are essentially indistinguishable, using standard microscopic examination methods.

If required, cultured specimens can provide additional characteristics that will enable technicians to determine what genus is represented. If sporulating structures are present, Aspergillus is readily identifiable on tape samples. [Discovery of the Aspergillus species requires the culture of the fungus under different conditions of media, humidity, and temperature. Identifying Penicillium species is difficult, but, in some cases, possible.]

These two allergenic molds are among those most often found in contaminated buildings. Aspergillus is represented by numerous species, many of which produce toxic substances. It may be associated with symptoms such as sinusitis, allergic bronchiopulmonary aspergillosis, and other allergic symptoms. As if not to be outdone, Penicillium too is found in increased numbers in interiors. Some of its many species produce toxic substances that can cause allergic reactions, mucous membrane irritation, headaches, vomiting, and diarrhea.

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Aspergillus penicilloides
Conidia dimensions: 3-3.5 x 4-5 microns. Can grow in areas with low water activity. It is found in house dust and food.

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Aspergillus restrictus
This species is only occasionally pathogenic.

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Aspergillus
Aw 0.75 - 0.82. Reported to be allergenic. Members of this genus are reported to cause ear infections. Many species produce mycotoxins that may be associated with disease in humans and other animals. Toxin production is dependent on the species or a strain within a species and on the food source for the fungus. Some of these toxins have been found to be carcinogenic in animal species. Several toxins are considered potential human carcinogens. Common cause of extrinsic asthma (immediate-type hypersensitivity: type I). Acute symptoms include edema and bronchiospasms; chronic cases may develop pulmonary emphysema; may also be associated with sinusitis, allergic bronchiopulmonary aspergillosis, and other allergic symptoms.

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Aspergillus sydowi
This species is only occasionally pathogenic.

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Aspergillus terreus
Aw 0.78. Conidia dimensions: 1.8-2.4 microns or 2 - 2.5 microns. Aleurospores 6 - 7 microns in diameter are also produced. Found in warmer soil and in grains, straw, cotton and decomposing vegetation. Can produce the toxin patulin and citrinin that may be associated with disease in humans and other animals. This fungus is associated with aspergillosis of the lungs and or disseminated aspergillosis. Found as an isolate from otomycosis - ear infection, and onychomycosis - infection of finger or toenails.

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Aspergillus ustus
This species is only occasionally pathogenic.

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Aspergillus versicolor
Aw 0.78. Conidia dimensions: 2-3.5 microns. Mostly in temperate zones, it is commonly found in air, house dust, foods (including dairy products), soil, hay, and cotton. It sometimes produces the mycotoxin "sterigmatocystin", which can cause diarrhea and upset stomach, and is a possible carcinogen, affecting the liver and kidneys. Various other toxins are associated with A. versicolor,such as aspercolorin, averufin, cyclopiazonic acid, and versicolorin. Additionally, the volatile organic compound (VOC) "geosmin" is generated by the action of this mold. Often an irritant to mucus membranes of humans and pets, geosmin has a musty, earthy odor.

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Aureobasidium
Found in soil, forest soils, fresh water, aerial portion of plants, fruit, marine estuary sediments, wood. Allergen, Type I allergies (hay fever, asthma). Type III hypersensitivity pneumonitis: "humidifier fever", "sauna taker's lung". Growth indoors is widespread where moisture accumulates- especially bathrooms and kitchens- on shower curtains, tile grout, windowsills, textiles, liquid waste materials. Potential toxic production is not known. Rare reports of: isolates from skin lesions, keratitis, spleen abscess in a lymphoma patient, blood isolate from a leukemic patient.

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Basidiomycetes
Taxonomic designation for fungi of the subdivision "Basidiomycotina", which includes mushrooms and puffballs. They produce spores that are formed on the outside of a special cell, called the "basidium".

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Basidiospore
An exogenous sexual spore (meiospore) borne on a basidium. Or, a spore from a basidiomycete (a member of Basidiomycetes). Many varieties are reported to be allergenic.

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Bipolaris
A fungus with large spores that could be expected to be deposited in the upper respiratory tract. This fungus can produce the mycotoxin - sterigmatocystin, which has been shown to produce liver and kidney damage when ingested by laboratory animals.

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Blastomyces
Human pathogen. The fungus is commonly found in soil. It is a dimorphic fungus that has filamentous fungus when grown at 25 degrees C. and a yeast form at 37 degrees C.

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Botrytis
Aw 0.93. Conidia dimensions: 7-14 x 5-9 microns. It is parasitic on plants and soft fruits. Found in soil and on house plants and vegetables, it is also known as "gray mold". It causes leaf rot on grapes, strawberries, lettuce, etc. It is a well-known allergen, producing asthma type symptoms in greenhouse workers and the symptoms of "wine grower's lung".

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Candida
Part of the normal flora of mouth and other mucous membranes in the body. Thrush and other diseases caused by Candida albicans usually occur after prolonged treatment with antibiotics or steroids. The environment is not a likely source of exposure for this fungus. Cells from the organism are usually not airborne. Reported to be allergenic.

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Cephalosporium
See Acremonium

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Chaetomium
Large ascomycetous fungus producing perithecia. It is found on a variety of substrates containing cellulose, including paper and plant compost. It has been found on paper in sheetrock. It can produce anAcremonium-like state on fungal media. Varieties are considered allergenic and have been associated with peritonitis, cutaneous lesions, and system mycosis.

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Cladosporium fulvum (Fulvia fulva)
Conidia dimensions: 12-47 x 4-10 microns. It is found on the leaves of tomatoes.

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Cladosporium herbarum
Aw 0.88. Conidia dimensions: 5-23 x 3-8 microns. It is found on dead plants, woody plants, food, straw, soil, paint and textiles.

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Cladosporium macrocarpum
Conidia dimensions: 9-29 x 5-13 microns. It is found on dead plants, woody plants, food, straw, soil, paint, and textiles.

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Cladosporium (Hormodendrum)
Aw 0.88; Aw 0.84. Most commonly identified outdoor fungus. The outdoor numbers are reduced in the winter. The numbers are often high in the summer. Often found indoors in numbers less than outdoor numbers. It is a common allergen. Indoor Cladosporium sp. may be different than the species identified outdoors. It is commonly found on the surface of fiberglass duct liners in the interior of supply ducts. A wide variety of plants are food sources for this fungus. It is found on dead plants, woody plants, food, straw, soil, paint, and textiles. Produces greater than 10 antigens. Antigens in commercial extracts are of variable quality and may degrade within weeks of preparation. Common cause of extrinsic asthma (immediate-type hypersensitivity: type I). Acute symptoms include skin lesions, eye ulceration, mycosis (including onychomycosis, an infection of the nails of the feet or hands) edema and bronchiospasms; chronic cases may develop pulmonary emphysema.

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Cladosporium sphaerospermum
Conidia dimensions: 3-4.5 microns. It is found as a secondary invader of plants, food, soil, paint and textiles.

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Conidium
A thin-walled, asexual spore borne exogenously on an often specialized hypha (conidiophore) and is deciduous at maturity. (plural form: conidia.)

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Conidia, unidentified
These are mold spores that do not show morphological characteristics that allow identification. Because there are tens of thousands of types of fungi, many fall into the "other" or "unknown" category. If they are present in significant numbers, additional measures can be taken to identify them. When spore counts are listed in the category: "Unidentified Conidia" their numbers are considered "normal".

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Conidobolus
Can cause a chronic inflammatory disease of the nasal mucosa (entomophthoromycosis).

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Cryptococcus neoformans
A basidiomycetous encapsulated fungal organismfound worldwide, mainly around pigeon roosts and soil contaminated with decaying pigeon or chicken droppings. It is generally accepted that the organism enters the host by the respiratory route in the form of a dehydrated haploid yeast or as basidiospores. Hematogenously spreading to extrapulmonary tissues, its predilection for the brain means infected persons usually contract meningoencephalitis, which can be fatal.

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Cryptostroma corticale
Conidia dimensions: 4-6.5 x 3.5-4 microns. Found on the bark of maple and sycamore trees and on stored logs.

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Cunninghamella
Can cause disseminated and pulmonary infections in immune compromised hosts.

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Curvularia
Reported to be allergenic and has been associated with allergic fungal sinusitis. It may cause corneal infections, mycetoma, and infections in immune compromised hosts.

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Dreschlera
Conidia dimensions: 40-120 x 17-28 microns. Found on grasses, grains and decaying food. It can occasionally cause a corneal infection of the eye.

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Epicoccum
Conidia dimensions: 15-25 microns. A common allergen. It is found in plants, soil, grains, textiles and paper products.

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Epidermophyton
Can cause infections of skin (including ringworm) and nails.

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Fungus
Neither animals nor plants, these saprophytic and parasitic spore-producing organisms rate a taxonomic kingdom of their own. Fungi include molds, rusts, mildews, smuts, mushrooms, puffballs, and yeasts. It is estimated that more than 1.5 million species of fungi exist.

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Fusarium solani
Aw 0.90. Macroconidia dimensions: 27-52 x 4.4-6.8; Microcondia dimensions: 8-16 x 2-4 microns. Found in plants and soils. Can produce trichothecene toxins that may be associated with disease in humans and animals.

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Fusarium
Aw 0.90. A common soil fungus. It is found on a wide range of plants. It is often found in humidifiers. Several species in this genus can produce potent trichothecene toxins. The trichothecene (scirpene) toxin targets the following systems: circulatory, alimentary, skin, and nervous. Produces vomitoxin on grains during unusually damp growing conditions. Symptoms may occur either through ingestion of contaminated grains or possibly inhalation of spores. The genera can produce hemorrhagic syndrome in humans (alimentary toxic aleukia). This is characterized by nausea, vomiting, diarrhea, dermatitis, and extensive internal bleeding. Reported to be allergenic. Frequently involved in eye, skin, and nail infections.

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Geotrichum
Aw 0.90. Conidia dimensions: 6-12 x 3-6 microns. Aw 0.90. A common contaminant of grains, fruits, dairy products, paper, textiles, soil, and water; often present as part of the normal human flora. The species Geotrichum candidum can cause a secondary infection (geotrichosis) in association with tuberculosis. This rare disease can cause lesions of the skin, bronchi, mouth, lung, and intestine.

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Gliocladium
A fungus that is structurally similar to Penicillium sp. It is reported to be allergenic.

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Helicomyces
A mitosporic mold often encountered on decaying plant matter. The genus name prefix "helico" is derived from the shape of the mold's microscopic structure; certain filaments (sometimes the conidia) curve into a helical path.

Reported effects upon human health in the indoor environment are not available at this time.

Scientists have shown the interaction of Helicomyces roseus with nitrogen-fixing bacteria to be a vital component of an effective soil enriching system (where sugar cane litter is the decomposition target).Helicomyces lilliputeus has long been known as an important sewage treatment systems decomposer, so it is not unexpected that other members of this genus have been observed living on wood submerged in water.

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Helminthosporium
Reported to be allergenic.

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Histoplasma
A fungus that has filamentous growth at 25 degrees C. and yeast growth at 37 degrees C. It is reported to be a human pathogen. It may be associated with birds.

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Humicula
Grows on products with a high cellulose
content. These fungi are also found in soil and on plant debris.

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Hyaline mycelia
Mycelia that are transparent, translucent, or colorless. If no reproductive structures are present, identification is difficult. Often associated with allergic symptoms.

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Memnoniella
A cellulolytic fungus that is very closely related to Stachybotrys sp. Both fungi have a worldwide distribution and are often found together and are commonly found in soil. Recent studies on mycotoxins revealed that Memnoniella echinata can have a toxicity similar to that of some isolates of Stachybotrys chartarum. Both produce varying amounts of simple trichothecenes. Thus, it is suggested thatMemnoniella sp. should also be considered potentially dangerous in indoor air. The major difference between the two fungi is that the conidia of Memnoniella sp. are in long persistent chains while those ofStachybotrys are aggregated in slimy heads. Also the aerodynamic diameter of Memnoniella sp. conidia is smaller and it would be expected to have an even greater potential to penetrate deep into lungs than the conidia of Stachybotrys sp.

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Microsporum
Causes ringworm in humans.

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Mold
Molds are a group of organisms that belong to the taxonomic kingdom of Fungi. There are over 20,000 species of mold. Molds reproduce by making spores. Mold spores waft through the indoor and outdoor air continually. When mold spores land on a damp spot indoors, they may begin growing and digesting whatever they are growing on. Molds can grow on virtually any organic substance, as long as moisture and oxygen are present.

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Monilia
Reported to be allergenic. This fungus produces soft rot of tree fruits. Other members produce a red bread mold. It is infrequently involved in corneal eye infections.

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Mucor
Often found in soil, dead plant material, horse dung, fruits and fruit juice. It is also found in leather, meat, dairy products, animal hair, and jute. A Zygomycetes fungus that may be allergenic (skin and bronchial tests). This organism and other Zygomycetes will grow rapidly on most fungal media. May cause mucorosis in immune compromised individuals. The sites of infection are the lung, nasal sinus, brain, eye, and skin. Infection may have multiple sites.

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Mycelium
A mass of interwoven hyphae (a hypha is a filamentous part of a fungus that usually has several cells in linear succession with dividing walls in between) that is often submerged in soil or organic matter or the tissues of a host.

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Myxomycetes
A taxonomic designation for fungi that are included in the category of "slime molds". They're occasionally found indoors, but mainly reside in forested regions on decaying logs, stumps, and dead leaves. Myxomycetes display characteristics of fungi and protozoans. In favorable (wet) conditions they exhibit motile, amoeba-like cells, usually bounded only by a plasma membrane, that are variable in size and form. During dry spells, they form a resting body (sclerotium) with dry, airborne spores. These fungi are not known to produce toxins, but can cause hay fever and asthma.

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Nigrospora
Commonly found in warm climates, this mold may be responsible for allergic reactions such as hay fever and asthma. It is found on decaying plant material and in the soil. It is not often found indoors.

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Oidium
The asexual phase of Erysiphe sp. It is a plant pathogen causing powdery mildews. It is very common on the leaves stems, and flowers of plants. The health effects and allergenicity have not been studied. It does not grow on non-living surfaces such as wood or drywall.

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Paecilomyces
Commonly found in soil and dust; less frequently in air. P. variotii can cause paecilomycosis. Linked to wood-trimmer's disease and humidifier associated illnesses. They are reported to allergenic. Some members of this genus are reported to cause pneumonia. It may produce arsine gas if growing on arsenic substrate. This can occur on wallpapers covered with Paris green.

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Papulospora
These fungi are found in soil, textiles, decaying plants, manure, and paper.

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Penicillium
Aw 0.78 - 0.88. A wide number of organisms have been placed in this genus. Identification to species is difficult. Often found in aerosol samples. Commonly found in soil, food, cellulose and grains. It is also found in paint and compost piles. It may cause hypersensitivity pneumonitis, allergic alveolitis in susceptible individuals. It is reported to be allergenic (skin). It is commonly found in carpet, wallpaper, and in interior fiberglass duct insulation. Some species can produce mycotoxins. Common cause of extrinsic asthma (immediate-type hypersensitivity: type I). Acute symptoms include edema and bronchiospasms; chronic cases may develop pulmonary emphysema. It may also cause headaches, vomiting, and diarrhea.

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Periconia
Found in soil, blackened and dead herbaceous stems, leaf spots, grasses, rushes, and sedges. Almost always associated with other fungi. Rarely found growing indoors. Reportedly associated with a rare case of mycotic keratitis.

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Perithecium
A fruiting body of a fungus in which some types of spores (including ascospores) are produced. (plural form: perithecia)

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Peronospora
These species are plant pathogens and the genus is one that causes downy mildews. Peronospora is very common and is an obligate parasite (obligate parasites cannot grow on non living environmental surfaces) found on leaves, stems, flowers, and fruits of living higher plants. Peronospora sp. may be identified in air on spore trap samples since spores have a distinctive morphology. The spores may also be seen in dust as part of the normal influx of outdoor microbial particles. As of this writing, allergenicity has not been studied and no information is available regarding health effects or toxicity.

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Phaeohyphomycosis
A hyphomycosis (infection by a mold of the taxonomic designation "Hyphomycetes") in which the infiltrating microbes are usually of the mold family "Dematiaceae", and are characterized by the coloring of their mycelium; the prefix "phaeo" means "dusky-brown". Various forms of the disease involve different areas of the body, such as the skin or respiratory tract. Intrusion of the mold in the eye, brain, bone, or subcutaneous tissue typically occurs as a result of trauma to the affected area.

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Phoma
A common indoor air allergen that can cause hay fever, asthma, and a type of hypersensitivity pneumonitis commonly called "shower curtain disease" (shower surfaces being among those frequented by this fungal organism). Phoma infections in humans also have been reported; usually affecting the immunocompromised, they include mycotic keratitis (where it refers to an infection of the skin) and phaeohyphomycosis (see phaeohyphomycosis).

For a positive identification of this genus, the specimen must contain the pycnidia (a round to pear-shaped fruiting structure containing conidia) to confirm the presence of simple phialides (a cell from which conidia are extruded). A cultured sample would provide these components. Colonies are rapid growing, appear powdery to velvety, and exhibit many different colors. This mold is known to grow on butter, rice, potatoes, paint (sometimes seen as pink and purple spots on painted walls), cement, rubber, wood, paper, and under linoleum. In nature, the species are found in soil, manure, on fruit, dead plants, and as parasites on live plants.

Researchers have discovered that when Phoma macrostoma is sprinkled onto the soil in areas with no preexisting weeds, it acts as an earth-friendly herbicide, inhibiting the ability of many broadleaf plants (including dandelions) to produce chlorophyll; the young broadleaf plants turn white and die while grass seems to be unaffected.

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Pithomyces
A native of mostly tropical environments, it commonly grows on dead plants, soil, wood, and especially the dead leaves and grasses of livestock fodder. Pithomyces chartarum produces sporidesmin (a piperazinedione), a mycotoxin known to cause animal liver damage, and it causes facial eczema in cattle, sheep, and goats. For humans, it is considered a possible allergen, and a potential infectious agent in immunocompromised patients.

Not known to be prolific indoors, this mold can sometimes be found on paper. It exhibits distinctive multi-celled brown conidia.

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Rhizomucor
The Zygomycetous fungus is reported to be allergenic. It may cause mucorosis in immune compromised individuals. It occupies a biological niche similar to Mucor sp. It is often linked to occupational allergy. May cause mucorosis in immune compromised individuals. The sites of infection are the lung, nasal sinus, brain, eye, and skin. Infection may have multiple sites.

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Rhizopus
The Zygomycetous fungus is reported to be allergenic. It may cause mucorosis in immune compromised individuals. It occupies a biological niche similar to Mucor sp. It is often linked to occupational allergy. May cause mucorosis in immune compromised individuals. The sites of infection are the lung, nasal sinus, brain, eye, and skin. Infection may have multiple sites.

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Rhodotorula
A reddish yeast typically found in moist environments such as carpeting, cooling coils, and drain pans. In some countries it is the most common yeast genus identified in indoor air. This yeast has been reported to be allergenic. Positive skin tests have been reported. It has colonized terminally ill patients.

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Rusts(and smuts)
These fungi are associated with plant diseases. In the classification scheme of the fungi, the smuts have much in common with the rusts, and they are frequently discussed together. Both groups produce wind-borne, resistant teliospores that serve as the basis for their classification and their means of spread. Rusts usually attack vegetative regions (i.e., leaves and stems) of plants; smuts usually are associated with the reproductive structures (seeds). They can cause hay fever and asthma.

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Saccharomyces
Reported to be allergenic. Baker's yeast.

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Scopulariopsis
It may produce arsine gas if growing on arsenic substrate. This can occur on wallpapers covered with Paris green. It has been found growing on a wide variety of materials including house dust. It is associated with type III allergy.

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Sepedonium
Most easily recognized by the spores, which are colorless to yellow, spiny, round, 1-celled, and produced singly at the ends of short filaments. Sometimes phialides of the Acremonium or Gabarnaudiatype may also occur. A few species of Mortierella, as well as the human pathogen Histoplasma capsulatum, produce spores resembling those of Sepedonium. Isolated from soil, but most commonly parasitized mushrooms.

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Serpula lacrymans
Common cause of extrinsic asthma (immediate-type hypersensitivity: type I). Acute symptoms include edema and bronchiospasms; chronic cases may develop pulmonary emphysema.

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Smuts
See rusts.

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Spore
The means by which molds reproduce. Spores are microscopic (2-100 micrometers) and various shapes. Distribution can be accomplished by a breeze, water droplet, or a person or animal passing by. They can even be discharged by the mold (usually under moist conditions or high humidity).

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Sporobolomyces
Reported to be allergenic.

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Sporothrix
The species Sporothrix schenckii can cause sporotrichosis, but usually only in individuals that are immune compromised. Sporotrichosis is a chronic fungal infection that results when the mold enters the body where the skin is damaged or via the lungs. If it reaches the bloodstream, it can affect many other parts of the body.

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Sporotrichum
Reported to be allergenic. Additionally, Sporotrichum pruinosum has been observed in the respiratory secretions of some human patients, indicating a possible ability to colonize the bronchopulmonary pathways. This genus does not cause sporotrichosis (see also Sporothrix, for there is some taxonomic confusion between these two genera).

Rarely found in cooler regions, Sporotrichum is prevalent in warm-temperate and tropical zones, and grows (rapidly) on soils, decaying plant matter, wet or rotting wood, grasses, and landscaping mulch. Colonies may appear white, rosy-beige, or orange, and have a velvety to granular texture.

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Stachybotrys
Aw - 0.94 , optimum Aw ->0.98. Several strains of this mold (S. atra, S. chartarum, and S. alternans are synonymous) may produce macrocyclic trichothecenes (one of which is Satratoxin H) that are poisonous by inhalation. These mycotoxins, when present, are primarily associated with the mold's spores.

Individuals with chronic exposure to Stachybotrys's toxins reported cold and flu symptoms, sore throats, diarrhea, headaches, fatigue, dermatitis, hair loss, general malaise, and psychological depression. For infants, the toxins create a vulnerability to a serious condition called pulmonary hemosiderosis (bleeding in the lungs) where severe bleeding can result in coughing blood or nosebleeds, and low grade bleeding can cause chronic coughs and congestion with anemia. People who unknowingly handled material contaminated with this mold described symptoms of cough, rhinitis, burning sensations of the mouth and nasal passages, and cutaneous irritation at the point of contact, especially in areas of abundant perspiration. The toxins produced by this mold will suppress the immune system, affecting the lymphoid tissue and the bone marrow. Animals injected with macrocyclic trichothecenes exhibited the following symptoms: necrosis and hemorrhage within the brain, thymus, spleen, intestines, lung, heart, lymph nodes, liver, and kidneys.

This is a dark-colored fungus that grows on building materials with a high cellulose content and a low nitrogen content. It is slow growing when compared to other common molds, and may not appear to compete well in their presence. Yet, when moisture levels are high for prolonged periods, Stachybotrysmay gradually become the dominating genus (possibly because of its yield of mycotoxins, which are believed to be directed against other molds and bacteria). This organism is usually difficult to find in indoor air samples unless it is physically disturbed, but when it does appear it is an alert to find the source, as it will likely be found growing in abundance. Its spores--which can be found in a gelatinous mass--will die readily after release, but are still allergenic and can be toxigenic. Areas with a relative humidity above 55%, and are subject to temperature fluctuations, are ideal for toxin production.

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Stemphylium
This genus is included in the taxonomic designation "Hyphomycetes". It is a known allergen, causing Type I allergies (examples: hay fever, asthma). Phaeohyphomycotic sinusitis has been reported in connection with this mold. (See phaeohyphomycosis.)

Existing mainly in the temperate northern hemisphere, it can be found in soil, moist wood or cellulose materials, on decomposing plants, and as pathogens on living plants (leaf spots are one example). Colonies grow rapidly, and appear velvety to cottony in texture; coloring is light brown or olive green to black. Though it is rare to find indoor colonization, it has been found in dust that is transferred in from outside, including dust on air filters.

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Syncephalastrum
Can cause a respiratory infection characterized by a solid intracaitary fungal ball.

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Torula
Found outdoors in air, soil, on dead vegetation, wood, and grasses. Also found indoors on cellulosic materials. Reported to be allergenic and may cause hay fever and asthma.

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Trichoderma
It is commonly found in soil, dead trees, pine needles, paper, and unglazed ceramics. It often will grow on other fungi. It produces antibiotics that are toxic to humans. It has been reported to be allergenic. It readily degrades cellulose.

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Trichophyton
Can cause ringworm, athlete's foot, jock itch, and other infections of the skin, nail, beard and scalp. Reported to be allergenic. Found on soil and skin.

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Trichothecium
Aw 0.90. Conidia dimensions: 12-23 x 8-10 microns. Found in decomposing vegetation, soil, corn seeds, and in flour. The species Trichothecium roseum can produce a trichothecene toxin that may be associated with disease in humans and other animals. Reported to be allergenic.

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Tritirachium
Reported to be allergenic.

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Ulocladium
Aw 0.89. This mold is reported to be a major allergen, capable of causing hay fever and asthma. It is also known to rarely cause subcutaneous infections. The University of Adelaide, Australia, categorizes this microbe in the classification group "Dematiaceous Hyphomycetes", which includes it as a possible causative agent of phaeohyphomycosis (see phaeohyphomycosis).

Widely distributed in nature and considered a saprobe (weak parasite), some of its growth sites are soil, grasses, dead or dying plants (mainly herbaceous vegetation), manure, and compost. In interior environments it has been found on paper, painted surfaces, gypsum board, textiles, jute, straw materials, carpets, cellulose building materials (including wood), and in dust and air samples. Colonies are moderately fast growing, usually appearing olive-brown (or rusty-brown) to black (or grayish), with a texture that is granular to velvety.

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Verticillium
Conidia dimensions: 2.3-10 x 1-2.6 microns. Found in decaying vegetation, on straw, soil and arthropods. A rare cause of corneal infections.

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Wallemia
Aw 0.75. Conidia dimensions: 2.5-3.5 microns. Found in sugary foods, salted meats, dairy products, textiles, soil, hay and fruits.

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Yeast
Various yeasts are commonly identified on air samples. Some yeasts are reported to be allergenic. They may cause problems if a person has had previous exposure and developed a hypersensitivity. Yeasts may be allergenic to susceptible individuals when present in sufficient concentrations.

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