Types of Molds
Alternaria sp.
Extremely widespread and ubiquitous. Outdoors it may be isolated from samples of soil, seeds, and plants. It is commonly found in outdoor samples. It is often found in carpets, textiles, and on horizontal surfaces in building interiors. Often found on window frames. The species Alternaria alternata is capable of producing tenuazonic acid and other toxic metabolites which may be associated with disease in humans or animals. Alternaria produces large spores having sizes between 20 - 200 microns in length and 7 - 18 microns in width, suggesting that the spores from this fungi are deposited in the nose, mouth, and upper respiratory tract. It may be related to bakers asthma. It has been associated with hypersensitivity pneumonitis, sinusitis, deratomycosis, onychomycosis, subcutaneous phaeohyphomycosis, and invasive infection. Common cause of extrinsic asthma (immediate-type hypersensitivity: type I). Acute symptoms include edema and bronchiospasms, chronic cases may develop pulmonary emphysema.
Aspergillus niger
This species is considered common to indoor environments. It is widespread in the soil and on plants and is also considered a common contaminant of foods. It has a musty odor. It is commonly found in the environment on textiles, in soils, grains, fruits and vegetables isolated from tropical and subtropical soils but less frequently from other areas. This fungus has an Aw (water activity) of 0.77 with an optimum > 0.97 . Conidia (spores) have dimensions of 3.5 - 5 microns or 4 to 5 microns. It is reported to be allergenic. It is common in secondary organisms following bacterial otitis and is more commonly being implicated in pulmonary disease in immunocompromised hosts. It has also been reported to cause skin infections.
Aspergillus sp.
A genus of fungi containing over 150 recognized species. Members of this genus have been recovered from a variety of habitats, but are especially common as saprophytes on decaying vegetation, soils, stored food, feed products in tropical and subtropical regions. Some species are parasitic on insects, plants and animals, including man. Species within this genus can grow in moist or somewhat drier conditions. All of the species contained in this genus should Toxin production is dependent on the species or a strain within a species and on the food source for the fungus.
Beauveria sp.
Commonly considered a contaminant. Known to be pathogenic in insects and especially silkworms; very rarely involved in infection of humans. Can be a cause of a Type 1 allergen (hay fever and asthma). Rare isolations from corneal lesions, and lungs from an immunocompromised patient. No toxic diseases have been documented to date to be caused from Beauveria.
Cladosporium sp.
The 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. Indoor species of Cladosporium species may be different than the species identified outdoors. It is commonly found on the surface of fiberglass duct lining 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. Cladosporium is generally regarded to be allergenic. Can be a cause of extrinsic asthma (immediate type hypersensitivity: Type I). Acute symptoms include edema and bronchiospasms, and chronic cases may develop into pulmonary emphysema. Exposure to Cladosporium has also been associated with skin lesions, keratitis, onychomycosis, sinusitis, and pulmonary infections.
Epicoccum nigrum
Common, no cases of infection have been reported in humans or animals.
Non-sporulating fungi
Results from unfavorable growth conditions. No fruiting structures are produced. Other common names include: Hyaline mycelia and mycelia sterilia. These are organisms that have not sporulated under the culture conditions provided. Most never sporulate in culture (sterile mycelia). Some represent nonsporulating colonies of common fungi. Growth on a variety of substrates. Identification is not possible without sporulation. Many Fungi do not adapt well to routine mycololgic media and growth conditions and therefore, may not sporulate. Specialized media, light-dark cycles, UV light, and low or high temperatures may be required to stimulate sporulation. Frequently non-sporulating colonies are produced by Basidiomycetes (mushrooms) which usually do not produce fruiting structures on lab media.
Penicillium sp.
The genus Penicillium is large and ubiquitous. It is believed to contain over 200 species, although only about 70 are of widespread interest. Some species are present in the soil while others prefer decaying vegetation. Still others are most commonly found in drier environments such as in seeds or wood. They are among the most common types of fungi found in indoor environments, particularly in basements. Because of their widespread nature, Penicillium species are frequent laboratory contaminants. Certain Penicillium species are known to be the causative agents of infection, e.g. cutaneous, eye, external ear, respiratory, and urinary tract infections. Many species are also known to produce mycotoxins. Immunocompromised individuals are particularly susceptible to disease induced by Penicillium species. Common symptoms of exposure to Penicillium species include headaches, edema, bronchiospasms, and vomiting.
Stachybotrys sp.
Aw (water activity) - 0.94, optimum Aw (water activity) - >0.98. Several strains of this fungus (S. atra, S. chartarum and S. alternans are synonymous) may produce a trichothecene mycotoxin- Satratoxin H - which is poisonous by inhalation. The toxins are present on the fungal spores. This is a slow growing fungus on media. It does not compete well with other rapidly growing fungi. The dark colored fungi grows on building material with a high cellulose content and a low nitrogen content. Areas with relative humidity above 55% and are subject to temperature fluctuations are ideal for toxin production. Individuals with chronic exposure to the toxin produced by this fungus reported cold and flu symptoms, sore throats, diarrhea, headaches, fatigue, dermatitis, intermittent local hair loss, and generalized malaise. The toxins produced by this fungus will suppress the immune system affecting the lymphoid tissue and the bone marrow. Animals injected with the toxin from this fungus exhibited the following symptoms: necrosis and hemorrhage within the brain, thymus, spleen, intestine, lung, heart, lymph node, liver, and kidney. The mycotoxin is also reported to be a liver and kidney carcinogen. Affects by absorption of the toxin in the human lung are known as pneumomycosis. This organism is rarely found in outdoor samples. It is usually difficult to find in indoor air samples unless it is physically disturbed. The spores are in a gelatinous mass. Appropriate media for the growth of this organism will have a high cellulose content and a low nitrogen content. The spores will die readily after release. The dead spores are still allergenic and toxigenic. Percutaneous absorption has caused mild symptoms.
Ulocladium sp.
Commonly considered a contaminant. Found in soil, dung, paint, and grasses. Not known to cause health issues.
Yeast
Various yeasts are commonly identified on air samples. Some yeasts are reported to be allergenic. Health problems may be caused if a person has had repeated exposure to the organisms causing a hypersensitivity.