There are reportedly seven different types of species, of which, Areobasidium pullulans is probably the most common. This fungus is found outdoors in soil and on leaves of oak, beech, maple, and poplar trees. Found indoors on condensation areas, moist building materials, moist windowsills or frames, silicon seals, shower curtains, and painted surfaces. As the species matures it becomes a dark olive brown that appears glassy smooth and wet. Due to it’s slime-like composition, these species can sometimes be mistaken for a black yeast during the identification process.
The laboratory reports Acremonium/Verticillium as one genus grouping because with the method of non-viable microbiological analysis, Acremonium and Verticillium cannot be easily differentiated by their morphology. The fungus Acremonium has been reported to be allergenic. Isolates have been reported to produce a toxin from the trichothecene group, which is toxic if ingested. It has been associated with households where occupant complaints were nausea, vomiting and diarrhea. It has also been reported to cause mycetomas, infections of the cornea and nails. This fungus can be parasitic to plants or saprophytic. Verticillium is a widespread mitosporic (lacks a sexual state) fungus found on soils and decaying plant matter in temperate to subtropical to tropical areas. This saprobe (weak parasite) requires wounds in order to infect a host. It causes the plant disease Verticillium Wilt, which affects many mild-climate plants in hot weather and is characterized by wilt, dulling or yellowing of leaf color and withering near the base. Some species are parasites of other fungi and insects (arthropods). Verticillium is generally considered to be nonpathogenic, but a few cases of keratitis (eye infection) have been reported. This genus can produce an antifungal compound (vergosin), an antitumor antibiotic, and other compounds that have industrial uses.
Alternaria is a large and widespread genus, the conidia of which are easily carried by the wind, with peak concentrations in the summer and early fall. Alternaria is commonly found in house dust, carpets, textiles, on horizontal surfaces in building interiors, and window frames. It is one of the main fungal causes of allergy, being a common type I & III allergen. Outdoors, it may be isolated from samples of soil, seeds and plants, and is frequently reported in air. The large spore size suggests that this fungus will deposit in the nose, mouth and upper respiratory tract causing nasal septum infections. It has also been associated with hypersensitivity pneumonitis. It is a common cause of extrinsic asthma. Acute symptoms include edema and bronchiospasms; chronic cases may develop pulmonary emphysema. Baker’s asthma is associated with inhalation of Alternaria conidia present in flour. Other diseases caused by Alternaria include: Farmer’s lung, mycotic keratitis, skin infections, and osteomyelitis. Also, the species A. alternata is capable of producing tenuazonic acid and other toxic metabolites that may be associated with disease in humans or animals. Several species are pathogenic to plants and contribute to the spoilage of agricultural products. Alternaria has been isolated from substrates such as sewage, leather, stone monuments, optical instruments, cosmetics, computer disks, and jet fuel.
Arthrinium is a filamentous fungus that is found in most parts of the world and under varied ecological conditions. It is mainly found in soil and decaying plant material, especially grasses and sedges, and they are often captured from air near grassy places in temperate seasons. Although there are no reported infections caused due to Arthrinium, one species, Arthrinium sphaerospermum, has been reported as an allergen. The colonies of Arthrinium exhibit cotton-like physical characteristics and show white coloration with brown spots on the surface. The reverse side is pale.
Ascospores are a general category of spores that have been produced by means of sexual reproduction (in a sack-like structure called an ascus). Many are ubiquitous, saprophytic (an organism, that grows on and derives its nourishment from dead or decaying organic matter), and plant pathogens. This group contains potential opportunistic pathogens and toxin producers, which is dependant on genus and species. A rupture in the top portion of the ascus disperses the spores during rain or in times of high humidity.
The laboratory reports Aspergillus/Penicillium as one genus grouping because with the method of non-viable microbiological analysis, Aspergillus and Penicillium cannot be easily differentiated by their morphology. Some species of Aspergillus are considered serious, so for an exact determination, an Aspergillus species can be isolated using the Anderson Air Sampling method for culturable analysis. There are more than 160 different species of Aspergillus, sixteen of which have been documented as etiological agents of human disease. The diseases caused by species of Aspergillus are relatively uncommon and seldom occur in individuals with normally functioning immune systems. In addition, this genus has been reported to be allergenic. Many species produce mycotoxins that may be associated with diseases in humans and other animals. Toxin production is dependent on the species or strain within the species and on the food source for the fungus. Aspergillus tends to colonize continuously damp materials such as damp wallboard and fabrics. Penicillium is commonly found in house dust, on water-damaged wallpaper, behind paint and in decaying fabrics.
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.
This species may be recovered from the indoor environment. It has worldwide distribution but is predominantly a tropical to subtropical fungus apparently more common in cultivated than uncultivated soil. It colonizes on decaying vegetation, crop seeds and many other substrates. It grows on moldy corn and peanuts and can also be found in other foods and dairy products. It has been reported in water-damaged carpets. It has also been reported as an insect and animal pathogen. This fungus has an Aw (water activity) of 0.78. and conidia (spores) dimensions 3-6 microns or 3-5 microns. This fungus should be considered allergenic. Its presence has been associated with reports of asthma. Approximately 50% of the strains are capable of producing a group of mycotoxins – in the aflatoxin group. Aflatoxins are known animal carcinogen. There is limited evidence to suggest that this toxin is also a human carcinogen. The production of the fungal toxin is dependent on the growth conditions and on the substrate used as a food source. The toxin is poisonous to humans by ingestion and may directly affect the liver. Experiments have indicated that it is teratogenic and mutagenic. This fungus may also result in disease via inhalation and 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.
This species considered common to indoor environments. It occurs predominantely in tropical and subtropical regions in stored foods and feedstuffs such as wheat, corn, barely, sorghum, rice, peanuts, dried macaroni and spaghetti, refrigerated dough products, and flour. It has also been isolated from soils. It has an Aw (water activity) of 0.75 and Conidia (spores) dimensions 2.5-4 microns. This fungus should be considered allergenic. This species has been reported as an opportunistic pathogen including onychomycosis, otomycosis, and invasive aspergillosis. It has also been reported to produce the toxin petulin, which may be associated with disease in humans and other animals.
Aspergillus versicolor is commonly found in temperate environments, including house dust, air, food, soil, hay, cotton, and dairy products. Conidia dimensions typically range from 2 – 3.5 microns with a water activity level of 0.78. The detection of Aspergillus versicolor can indicate the presence of water damaged building materials when present in indoor environments. The species can potentially be an opportunistic pathogen, irritate mucus membranes of humans and pets through the production of mVOCs, as well as produce the mycotoxin, sterigmatocysin, which has the potential to cause diarrhea, upset stomach, and has been reported carcinogenic to the kidney and liver.
Basidiospores are a member of the family Basidiomycetes. Basidiomycetes are a decay type fungus, and depending on the actual species, the severity of decomposition can vary, however, they are typically found as mild wood decaying fungi. There are no known malignant, or serious health effects associated with Basidiospores, but they are known to be allergenic to sensitive individuals.
It is parasitic on plants, vegetables, and soft fruits but may also be found in soil. Reported to be allergenic. No toxic or invasive diseases have been documented to date.
This fungus is approximately 2.5m in size and doesn’t generally grow at temperatures above 32degrees Celsius. As an insect parasite, it is found almost anywhere that has a high insect population. This fungus is a slow growing colonizer and can have a white powdery appearance that aerosolizes easily and is reported to be a very strong allergen.
Bipolaris has more than 40 different species and was previously called thin and appears fluffy or velvety. It is associated with cereals and grasses. Bipolaris is a plant pathogen that may cause allergies and has been associated with nasal fungal sinusitis.
This genus contains a variety of organisms that have been isolated from the environment, as well as human skin and mucous membranes.
Chaetomium is found worldwide on a variety of substrates including paper, damp sheetrock, carpet, plant compost, soil, and between layers of wet plywood. Several species have been reported to play a major role in decomposition of cellulose-based materials, and is often found indoors with Stachybotrys. These fungi are able to dissolve the cellulose fibers in cotton and paper and thus cause the materials to disintegrate. The process is especially rapid under moist conditions. During the Second World War, countries lost a great deal of equipment to these species. Chaetomium is reported to have type I & III allergens, and can produce sterigmatocystin, a mycotoxin shown to cause kidney and liver damage in laboratory animals. It is not a common human pathogen, but it has been known to cause skin and nail infections.
Chrysosporium has about twenty-two different species and was previously called Aleurisma, Geomyces, Glenosporella, and Myceliophthora. It is considered a medium to fast grower and can produce white, tan, beige, pink, light gray, yellow, or olive colors. This species can be found in soils, plant debris, animal dung, birds, and leather. Most opportunistic at approximately 37 degrees Celsius and may cause skin infections in dogs and nail or skin infections in humans.
Cladosporium is widely distributed in air and rotten organic material. C. herbarum is the most frequently found species in outdoor air in temperate climates. It is often found indoors, usually in lesser numbers than outdoors. The dry conidia become easily airborne and are transported over long distances. This fungus is often encountered in dirty refrigerators, especially in reservoirs where condensation is collected. It can easily be seen on moist window frames covering the whole painted area with a velvety olive-green layer. Cladosporium often discolors interior paint, paper, or textiles stored under humid conditions. Houses with poor ventilation, houses with thatched straw roofs and houses situated in damp environments may have heavy concentrations of Cladosporium, which will be easily expressed when domestic mold is analyzed. It is commonly found on the surface of fiberglass duct liner in the interior of supply ducts. It is also found naturally on dead & woody plants, food, straw, soils, paint, and textiles. The ability to sporulate heavily, ease of dispersal, and buoyant spores makes this fungus the most important fungal airway allergen; and together with Alternaria, it commonly causes asthma and hay fever in the Western hemisphere. A few species of this genus cause disease, which range from phaeohyphomycosis, a group of mycotic infections characterized by the presence of demataceous septate hyphae. Infections of the eyes and skin by black fungi (also classified as phaeohyphomycosis), and chromoblastomycosis, chronic localized infection of the skin and subcutaneous tissue that follows the traumatic implantation of the etiologic agent are also caused by this fungus. Chromoblastomycosis lesions are verrucoid, ulcerated, and crusted. Skin abscesses, mycotic keratitis and pulmonary fungus ball have been recorded in immunocompromised patients. It may also cause corneal infections and mycetoma, characterized by localized infections that involve cutaneous and subcutaneous tissue, fascia, and bone consisting of abscesses, granulomata, and draining sinuses, usually in immunocompromised hosts. Cladosporium produces the toxins cladosporin and emodin, but neither of these is very toxic.
Widespread distribution. Together with C. herbarum compose the most common species on dead organic matter and in the air. It is found on dead plants, woody plants, food, straw, soil, paint and textiles. Reported allergen. Has been implicated in pulmonary and cutaneous infections, possible sinus infection, mixed disseminated infections. No toxic diseases have been documented to date.
Cryptococcus are yeast that produce by budding which appear smooth, slimy, shiny, and primarily cream colored. Although the color may differ depending on the cellulose material being digested. These species may be found in pigeon droppings, rotting vegetables, fruits, fruit juices, wood and dairy products. Inhalation can cause subacute, chronic or fatal meningitis. May spread in vascular system to the brain, kidneys, prostate, and skeletal areas. Skin infections may show acne-like lesions or ulcers.
Curvularia is reported to be a common type I allergen and is pathogenic to soil, plants, and cereals in tropical and subtropical areas. It is an opportunistic leaf spot fungus and weak pathogen, which survives as a saprobe, and is easily isolated from dead turf and weakened and/or dead plant tissue. Some species of Curvularia are known as storage molds of grains. This fungus may cause corneal infections, mycetoma and infections in immunocompromised individuals.
Conidia (spores) dimensions 40-120 x 17-28 microns. Found on grasses, grains and decaying food. It can occasionally cause a corneal infection of the eye.
Epicoccum is a dematiaceous, mitosporic fungi and is commonly found as a secondary invader in plants, soil, grains, textiles and paper products where Cladosporium and Aureobasidium are present. It is mostly saprophytic, or weakly parasitic. Epicoccum is frequently isolated from air and occasionally occurs in house dust. Epicoccum is reported to be a type I allergen, but not in a high frequency. Some allergenic symptoms are associated with the respiratory tract, and include allergic rhinitis, asthma, and hypersensitivity pneumonitis. These fungi can also produce antibiotic substances, which include flavipin, epicorazine A & B, and indole-3-acetonitrile. Due to the ability of this fungus to grow at 37°C, it can cause infection of skin in humans. Epicoccum is considered to be a dry weather spore and is very resistant to changes in water activity; the fungus has been known to resume growth after extended periods of drying. The spores are produced very rapidly and are at their peak from August to October.
Exophiala is a dematiaceous fungus widely distributed in soil, plants, decaying wood material, and water (especially surfaces in contact with cool, fresh water). As well as being a saprophyte (an organism able to extend its pathogenic action from dead or malnourished tissue to healthy tissue) in nature, it has been known to be involved in various human infections. Health effects include occasional mycetomas (specific infections of the skin and subcutaneous tissue.), chromoblastomycosis (a mycotic infection of the cutaneous and subcutaneous tissues), and other subcutaneous lesions. These infections are usually contracted through implantation and are associated with the existence or introduction of immunosuppression conditions, such as organ transplantation. As well as causing infection and abscess formation in subcutaneous tissues, prosthetic valvular vegetations, fungemia, and scattered infections due to Exophiala spp. have also been reported. At the present time, there is no information on the toxicity of Exophiala and its allergenic properties have not yet been studied. Exophiala may be identified on surfaces by tape lifts, tease mounts from bulk samples, and in air by culturable (Andersen) sampling.
Fusarium is a type I allergen and is an opportunistic pathogen commonly found in soil, plants, grains, and often in humidifiers. While most of the species are found in tropical and subtropical areas, some are found in the soil of cold climates. Some species are plant pathogens causing root and stem rot, vascular wilt or fruit rot, and all require extremely wet conditions for growth. This fungus is the most common cause of mycotic keratitis. It has been isolated from skin lesions of burn patients, nail infections, ear infections, varicose ulcer, mycetoma, osteomyelitis following trauma, and disseminated infections. Infections due to Fusarium are commonly referred to as fusariosis. This fungus produces very harmful toxins, especially in storage of infected crops. These toxins, known as trichothecenes (scierpene) target the circulatory, alimentary, skin, and nervous systems. Fusarium can also produce Vomitoxin, T-2 toxin, Fumonisin, and Zearalenone. Vomitoxin is produced on grains, which has been associated with outbreaks of acute gastrointestinal illness in humans. T-2 Toxin and related trichothecenes are some of the deadliest known toxins. If ingested in sufficient quantity, T-2 toxin can severely damage the entire digestive tract and cause rapid death due to internal hemorrhage. Fumonisin, commonly found in corn and corn based products, has recently been associated with outbreaks of veterinary mycotoxicosis causing “crazy horse disease”. Zearalenone toxin is similar in chemical structure to the female sex hormone estrogen and targets the reproductive organs. Fusarium is one of the most drug resistant fungi.
One of the most abundant basidiospores found in the atmosphere, Ganoderma basidiospores can be allergenic at high concentrations. Ganoderma basidiospores are released by “white-rot” mushroom genus Ganoderma P. that causes the decay of living trees and roots. The basidiospores are actively released from the mushroom’s basidium during periods of high humidity (night to pre-dawn hours) and are airborne (transported passively by wind), contributing significantly to the total air spora during late spring and fall. The presence of Ganoderma basidiospores in indoor air could mean two possibilities: a) air from outside blew in through an open entryway, thus transporting the spores, or b) the basidiospores were released by an indoor source, signifying the presence of Ganoderma P. on indoor woody plants or worse, on decaying structural wood.
Gliocladium is a widely distributed fungus commonly occurring in soil, decaying vegetation, as a parasite to other fungi. It is generally considered a contaminant. Gliocladium has not been reported as a disease causing agent for man or animal, however has been reported to cause type I allergens. This fungus can produce rapidly, spreading cottony colonies, which may begin as a white to cream color and become pink to rose; and matures to a dark green color. It is structurally similar to Penicillium sp., however collects in wet as opposed to dry masses, and therefore may not be easily detected in air samples.
Gonatobotryum is associated and is parasitic on the fungi Ceratocystis. Hence, it is found primarily where Ceratocytis grows: rotten wood of Quercus (Oak), Fagus (Beech), and other lumber. Black mold growths in boards in lumberyards as well as wood framing in home are almost always a congregation of both Gonatobotryum and Ceratocystis. Some species are parasitic on leaves of Hamamelis (Witch hazel), and have also been isolated from soil. Gonatobotryum spores and other structures are quite distinct and can be identified from surface (tape lifts, swabs) and air (spore trap) samples. Allergenicity and toxicity studies on Gonatobotryum are not currently available.
The genus Memnoniella is believed to be closely related to the genus Stachybotrys and is usually disseminated through the wind as a dry spore. Currently, there are no known allergens or pathogens associated with the genus. However, like Stachybotrys, Memnoniella may potentially produce the toxins trichothecene and griseofulvin. Similarly, they are categorized as a black mold.
Mitosporic Fungi (or Fungi Imperfecti)
The classification “Mitosporic Fungi” refers to those that do not form a clearly connected group, that is, they are not clearly related. However, these fungi all lack of an ability to reproduce sexually. Through recent molecular biological advances, it has been shown that Mitosporic Fungi are related most closely to Ascomycetes and Basidiomycetes. Mitosporic Fungi are used as biodeteriogens, a source of antibiotics, and in industrial chemicals. They are known to be casual agents of plant, animal, and human diseases.
The laboratory reports Mucor/Rhizopus as one genus grouping because with the method of non-viable microbiological analysis, Mucor and Rhizopus cannot be easily differentiated by their morphology. Mucor species are often found in soils, dead plant matter, and horse dung, fruits and fruit juice. It is almost always in house dust, frequently in air samples and old dirty carpets. Accumulated dust in ventilation ducts may contain high concentrations of viable Mucor spores. Asthmatic reactions to Mucor have been described. It is a Zygomycete fungus that may be allergenic (skin and bronchial tests). It is an opportunistic pathogenic organism and it may cause mucorosis in immune compromised individuals. The sites of infections are the lung, nasal sinus, brain, eye, and skin. Infection may have multiple sites. Rhizopus is prevalent in soil, fruit, animal and bird dung, foodstuffs, decaying materials, agricultural products (cereals, vegetables, etc.), house dust, and air. R. stolonifer (R. nigricans) is a common saprobe and facultative parasite of mature fruits and vegetables. The genus, Rhizopus, is reported to be a type I & III allergen often linked to occupational allergy. It may cause mucorosis in immunocompromised individuals. The species R. oryzae is often used in the production of fermented foods and alcoholic beverages; however, it also produces the ergot alkaloid agroclavine, which is toxic to humans and animals. It is the most frequently reported isolate of zygomycosis (mucormycosis), and represents ~60% of the zygomycosis cases and ~90% of the rhinocerebral cases. This disease is associated with acidotic diabetes, malnourished children, severely burned patients, diseases such as leukemia and lymphoma, immunosuppressive therapy, or use of cytotoxins and corticosteroids. The fungi show a propensity for vessel invasion resulting in embolization and necrosis of surrounding tissue. Rhizopus may also cause otomycosis, which is a mild or chronic infection of the external ear characterized by itching, inflammation, and accumulation of large masses of epithelial debris containing the fungi. This disease is found worldwide especially in tropical and subtropical areas, and in the southern to southwestern United States.
The laboratory reports Myxomycetes/Periconia/Smuts as one genus grouping because with the method of non-viable microbiological analysis their spores cannot easily be differentiated due to their similar round, brown morphology. Myxomycetes are found on decaying logs, stumps, and dead leaves, particularly in forested regions. Myxomycetes are not considered a true fungi, but characterized as a slime mold because they possess both wet and dry spore phases. Wet conditions produce a motile amoebic phase, and unfavorable dry conditions cause windborne dispersal of the dry fruiting body spores.
Smuts are found on cereal crops, grasses, weeds, and other fungi. Smuts are members of the Basidiomycetes group, with two spore types: teliospores, which occur in a dry powdery stage, and Basidiospores, which occur in a yeast stage. As parasitic plant pathogens, Smuts require a living host for the completion of their life cycle. Periconia are found on soil, blackened and dead plants, and are almost always associated with other fungi.
Myxomycetes and Smuts can cause Type I allergies, such as hay fever and asthma, but have not been reported as potential opportunists, pathogens, or toxin producers, and are therefore not considered a medical threat to humans. Periconia has not been studied as an allergen and produces no known toxin, though rare cases of mycotic keratitis have been reported.
Paecilomyces is a widespread fungus found in warm, arid regions in soil and plant debris, but also in decaying food or cosmetics, and dust, less frequently it is found in air. It is a secondary invader or saprobe on various plants, and some species are parasitic on insects. This fungus is considered to be thermo-tolerant. This is a clinical opportunistic fungus in the immunocompromised, causing endocarditis, keratitis, and peritonitis. P. variotii can cause paecilomycosis, and is linked to wood-trimmers disease and humidifier-associated illnesses. Some members of this genus are reported to cause pneumonia and pulmonary infections, mycosis, and other subcutaneous infections associated with lungs, skin and eyes. It may also cause toxicosis in humans and animals, especially dogs and cattle. Some of the toxins it produces include paecilotoxins, byssochlamic acid, variotin, ferrirubin, viriditoxin, indole-3-acetic acid, fusigen and patulin. It has type I & III allergens and has been reported as a causative agent of allergic alveolitis. It may produce arsine gas if growing on an arsenic substrate; this can occur on wallpapers covered with paris green.
A large number of organisms belong to this genus, and identification to species is difficult. Often found in aerosol samples, it is common in soil, food, cellulose, paint, grains, and compost piles. In the indoor environment it is in carpet, wallpaper, and in interior fiberglass duct insulation. Although this fungus causes fewer allergies than other molds, Penicillium is reported to be a type I & III allergen. It may cause hypersensitivity pneumonitis and allergic alveolitis in susceptible individuals. It can cause other infections such as keratitis, penicilliosis, and otomycosis. Some species can produce mycotoxins including Ochratoxin, which is damaging to the kidneys and liver and is also a suspected carcinogen; there is also evidence that impairs the immune system. It also produces Citrinin that can cause renal damage, vasodilatation, and bronchial constriction and Gliotoxin, which is immunosuppressive. Patulin is another of its mycotoxins that is believed to cause hemorrhaging in the brain and lungs and is usually associated with apple and grape spoilage. It can also cause extrinsic asthma. P. camemberti has been responsible for inducing occupational allergies among those who work with soft white cheeses on which the fungus grows (cheese washer’s lung). P. marneffei is the major pathogenic species causing infections of the lymphatic system, lungs, liver, skin, spleen, and bone, and is also the only species of the genus to have a yeast-like phase induced by temperature.
Phoma is a dematiaceous, filamentous fungus that can be found on plant material, soil, and in fruits as a parasite. Phoma is known widely as a plant pathogen (cases have been studied where Phoma has had a mycoparasitic affect on certain powdery mildews), but rarely causes infections in humans. Infections that can arise include rare skin irritations and subcutaneous phaeoghyphomycosis (mycotic infections characterized by the presence of dematiaceous (dark-walled) septate hyphae and sometimes yeast or a combination of both in tissue). This particular infection usually occurs after a considerable trauma and its development can be greatly affected by immunosupression. Phoma also acts as a Type I and Type II allergen. Growth areas of Phoma include ceiling tiles, the reverse side of linoleum, cement, paint, paper, wood, and wool. Air quality is not readily affected due to the fact that air currents do not disseminate spores. Phoma spores cannot be identified on spore traps, but can be on tape lifts if the spores and entire fruiting body are present. It also grows well on general fungal media.
Pithomyces is found growing on decaying plants, especially grasses, soil, and wood in tropical areas, it is rare in cold climates. It may grow on paper but is not prolific indoors. This fungus has demonstrated allergenic activity; it is also considered an etiologic agent in immunocompromised patients. The most common saprophytic species, P. chartarum produces a mycotoxin called sporidesmin (a piperazinedione) known to be pathogenic in animals causing liver damage and facial eczema, a condition of severe dermatitis in cattle, sheep, and goats. Pithomyces can be found on dead vegetative material in pastures, especially ryegrass. It favors warm, wet, humid weather, heavy dews, or irrigation.
The laboratory detected a considerable amount of basidiospores. Basidiospores belong to a family of fungi called Basidiomycetes, which are known to be a decay type fungus. Basidiomycetes are known allergens like all other molds, however there are no malignant or serious human health effects associated with it. The fact that the laboratory identified the basidiospores in very low levels in both the bulk and air samples can be understood with some detailed information on this particular family of fungi. One of the important characteristics of Basidiomycetes is that they don’t sporulate heavily, meaning that they don’t produce spores at a high rate. When a particular food source becomes scarce, that is when these Basidiomycetes begin to produce fruiting bodies, (i.e. mushroom caps) so that they can spread, propagate, and produce spores. In this situation, the wood floor is an ample food source for these Basidiomycetes, since it is cellulose based, which is a reason why fungal fruiting bodies are not observed.
Wood is naturally very durable in moderate, sheltered environments and it can last for thousands of years without substantial change. Biological deterioration is found principally in the form of insects and fungi; however, fungi are probably the agent of the greatest destruction of wood in nature and also in this case. Often, fungi damage wood, which makes it more inviting to insects, which completely consume wood like termites and beetle larvae. Most of the biological damage is started in poor environmental conditions for storage and display. Continuous biological decay is dependant upon four conditions. They are a supply of oxygen, moisture, food, and a moderate temperature range.
Dry rot, decay of seasoned wood caused by the attacks of any of a number of species of fungi, particularly Merulius lacrymans, Coniophora cerebella, and Poria incrassata, who are all members of the Basidiomycete family. These fungi penetrate to the interior of timbers and consume the cellulose in the wood fibers, leaving the timbers porous, although the wood may appear sound on the surface. The decay, dry rot, is so called because of the powdery appearance of the decayed wood, but the term is misleading because the fungi need water to live, and dry rot appears only in wood that has been exposed to moisture. Most decay fungi are unable to conduct water very far and can only attack moist wood. However, Poria incrassata, called dry rot or the water-conducting fungus, will decay wood, which would not be attacked by typical decay fungi. Poria infested wood is often mistakenly identified as subterranean termite damage. This type of fungus can transport water for several feet through large root-like structures called rhizomorphs. So naturally, Poria can be present and be attacking a distinct area, (i.e. the wood floor of the entry way), even though water or moisture intrusion may not be centralized or immediately accessible. Once established, it can quickly spread through a building and destroy large areas of flooring and walls in as little as a year or two.
Typically, infestations of Poria begin in dirt filled porches, damp crawl spaces and basements where wood is in contact with the soil. They also begin in moist concrete or damp bricks. When Poria infested wood dries it usually shrinks and cracks. The best indication for discovering a Poria infestation is either moisture content or relative humidity. The term “relative humidity” is derived from the relationship of moisture in the air and temperature of that air. In this case, the relative humidity under the house was 66.7%, compared to the outside (which is considered the norm or reference point), which was 58.9%. The simplest method to deter fungal and insect damage is to maintain and monitor a moderate environment. Out of the four above-mentioned biological factors that encourage wood decay, moisture content is the most controllable and feasible factor. There is almost no point trying to eradicate or exclude fungi, since they are so ubiquitous. However, we can successfully control their consumption of wooden objects. Simply put, if the relative humidity is kept moderate (less than 60%), there will be virtually no problems with fungi. Insects and fungi show little interest in penetrating paints and varnishes to consume wood. In conclusion, apart from the laboratory results, other vital signs insinuate that the fungus Poria incrassata is clearly the invader. Therefore, for this particular case, the severe parts of the infested wood floor should be removed and replaced, and the remaining should be treated with special chemicals, specifically designed to eliminate surface molds and decay fungi.
Rhizopus is prevalent in soil, fruit, animal and bird dung, foodstuffs, decaying materials, agricultural products (cereals, vegetables, etc.), house dust, and air. R. stolonifer (R. nigricans) is a common saprobe and facultative parasite of mature fruits and vegetables. The genus, Rhizopus, is reported to be a type I & III allergen often linked to occupational allergy. It may cause mucorosis in immunocompromised individuals. The species R. oryzae is often used in the production of fermented foods and alcoholic beverages; however, it also produces the ergot alkaloid agroclavine, which is toxic to humans and animals. It is the most frequently reported isolate of zygomycosis (mucormycosis), and represents ~60% of the zygomycosis cases and ~90% of the rhinocerebral cases. This disease is associated with acidotic diabetes, malnourished children, severely burned patients, diseases such as leukemia and lymphoma, immunosuppressive therapy, or use of cytotoxins and corticosteroids. The fungi show a propensity for vessel invasion resulting in embolization and necrosis of surrounding tissue. Rhizopus may also cause otomycosis, which is a mild or chronic infection of the external ear characterized by itching, inflammation, and accumulation of large masses of epithelial debris containing the fungi. This disease is found worldwide especially in tropical and subtropical areas, and in the southern to southwestern United States.
Scopulariopsis is ubiquitous and can be found on soil, plant material, feathers, insects, dung, house dust and on a wide variety of materials including old carpets and water-damaged wallpaper. The species S. fimicola is known as the white plaster mold of mushroom beds while other species may attack bee larvae and silkworms. Scopulariopsis is a type III allergen, and may cause a variety of infections in humans. It may cause onychomycosis (especially of the toenails), skin lesions, mycetoma, invasive sinusitis, keratitis, endophthalmitis, endocarditis, pneumonia, brain abscess and disseminated infections. Scopulariopsis may also cause pulmonary infections, such as an invasion of deep tissue including fungus balls in pre-formed pulmonary cavities. These are of primary concern to immune compromised hosts, and these infections may be highly fatal. The species Scopulariopsis brevicaulis may produce arsine gas if growing on building materials with an arsenic substrate, such as some types of wallpaper and paints.
Stachybotrys is commonly found in sub-tropical to tropical areas in soil and decaying plant materials, and is considered a type I & III allergen. Considerable recent media attention has been focused on the fungi Stachybotrys chartarum (atra) due to infant deaths in Cleveland from pulmonary hemosiderosis, which may be associated with contamination of residences with this fungus. Stachybotrys thrives on water damaged cellulose rich materials such as sheet rock, paper, ceiling tiles, cellulose containing insulation backing and wallpaper. The presence of this fungus in buildings is significant because of the mold’s ability to produce mycotoxins, such as Satratoxin H, Trichoverrol, and Cyclosporins that possess cytotoxic, immunological, carcinogenic effects. Exposure to these toxins can occur through inhalation, ingestion or dermal exposure. Symptoms include dermatitis, cough, rhinitis, nose bleeds, a burning sensation in the mouth and nasal passage, cold and flu symptoms, headache, general malaise, and fever. Inhalation of conidia may also induce pathological changes (pneumomycotoxicoses). Satratoxin H has been reported to be abortogenic in animals and in high doses or chronic low doses it can be lethal. S. chartarum (atra) produces other macrocyclic and trichoverroid trichothecenes and, like Memnoniella echinata, produces phenylspirodrimanes, which are immunosuppressive. Stachybotrys typically appears as a sooty black fungus occasionally accompanied by a thick mass of white mycelia. Memnoniella differs from Stachybotrys by producing conidia in chains. As a general rule, air sampling for Stachybotrys yields unpredictable results mainly due to the fact that this fungus is usually accompanied by other fungi such as Aspergillus and Penicillium that normally are better aerosolized than Stachybotrys. Bulk or surface sampling of suspect materials can be analyzed in a laboratory for identification by light microscopy. This fungus is a slow grower on media, therefore does not compete well with other rapidly growing fungi.
The laboratory reports Stemphylium/Ulocladium as one genus grouping because with the method of non-viable microbiological analysis, Stemphylium and Ulocladium cannot be easily differentiated by their morphology. Stemphylium is a decaying filamentous fungus that is considered ubiquitous and cosmopolitan. Spores can generally be found widely distributed on soil, wood, decaying vegetation, paper, textiles, and other cellulose materials. Stemphylium is a known allergen that can cause Type I allergies including hay fever and asthma, and may cause rare cases of phaeohyphomycotic sinusitis in humans, however identification has not been confirmed. Ulocladium is reported to be a major type I allergen. This saprobe (weak parasite) is widespread and commonly found on plant materials, soils, dung, grass, compost, and textiles. Some species are cellulolytic and can grow on water-damaged building materials. Ulocladium is also found in dust and air samples; and indoors on carpets and painted surfaces. This mitosporic (lacks a sexual state) fungus has been reported from cases of phaeohyphomycosis (cutaneous and subcutaneous infections caused by dematiaceous (dark-walled) fungi). Infection sites for susceptible hosts vary widely.
Trichoderma is one of the most widely spread soil fungi, frequently isolated from varied geographical locations. It colonizes dead leaves, fallen timber, compost heaps, and activated sludge. With other fungi Trichoderma species are highly aggressive. They have the ability to kill other fungi with their toxins, which include trichodermin and trichotoxin A, and then consume them using a combination of enzymes. Because it readily degrades cellulose, Trichoderma is often found in water or moisture damaged buildings.
Trichothecium is a filamentous mitosporic fungus is commonly considered a contaminant. The 2-celled colorless to pink spores (conidia) are commonly found in soil and decaying plant materials. The conidia dimensions are 12-23 x 8-10 microns and Water activity (Aw) is .90. The conidia are bilaterally symmetrical and are produced in long chains usually with the youngest spore being found at the bottom of the chain and attached at an oblique angle to the conidiophore. Trichothecium can be a parasite of fleshy fungi (macro fungi), where it can cover with a pink conidial dust. No human or animal diseases due to Trichothecium have been reported; however the species Trichothecium roseum can produce a trichothecene toxin which may be associated with disease in humans and other animals. No information is available regarding inhalation effects (allergenicity) or toxicity. Trichothecium is a fast colonizer (which means it can grow rapidly). Usually, colonization of media occurs between 25°C (77°F) and 36° (96.8°F). Trichothecium does not reportedly grow at 37°C (98.6°F), which is also the average body temperature. This species was formerly known as Cephalothecium.
Ulocladium is reported to be a major type I allergen. This saprobe (weak parasite) is widespread and commonly found on plant materials, soils, dung, grass, compost, and textiles. Some species are cellulolytic and can grow on water-damaged building materials. Ulocladium is also found in dust and air samples; and indoors on carpets and painted surfaces. This mitosporic (lacks a sexual state) fungus has been reported from cases of phaeohyphomycosis (cutaneous and subcutaneous infections caused by dematiaceous (dark-walled) fungi). Infection sites for susceptible hosts vary widely.
Verticillium is a widespread mitosporic (lacks a sexual state) fungus found on soils and decaying plant matter in temperate to subtropical to tropical areas. This saprobe (weak parasite) requires wounds in order to infect a host. It causes the plant disease Verticillium Wilt, which affects many mild-climate plants in hot weather and is characterized by wilt, dulling or yellowing of leaf color and withering near the base. Some species are parasites of other fungi and insects (arthropods). Verticillium is generally considered to be nonpathogenic, but a few cases of keratitis (eye infection) have been reported. This genus can produce an antifungal compound (vergosin), an antitumor antibiotic, and other compounds that have industrial uses.