Acremonium species

The genus Acremonium (formerly called Cephalosporium) are widespread occurring in soil and decaying plant material. The genus contains over 100 species. These fungi, being ubiquitous in the environment, are known to colonize the surfaces of many materials indoors as well as the HVAC systems of hospitals, schools, and commercial buildings. Acremonium species generally require moist conditions to amplify (grow) indoors. Identification to the species level, however, is difficult.

Disease Associations:

Several species are documented to cause onychomycosis (nail infections), corneal ulcers, and eumycotic mycetoma. Cases of meningitis and endocarditis have been reported particularly in the immuno-compromised host. Infections of artificial implants are occasionally reported.

Alternaria species

Alternaria species are one of the most abundant fungi in the atmosphere, they are predominantly isolated from various habitats; plants either as pathogens (common tomato pathogen) or saprobes, in the soil, on foodstuffs, and textiles. In most parts of the world, Alternaria may be identified from atmospheric sampling year-round, although highest overall concentrations often occur in summer and early fall in temperate areas.

Disease Associations:

Published reports suggest that a concentration >100 conidia/ of air may induce allergic symptoms. Cases of onychomycosis (nail infections), sinusitis, ulcerated cutaneous infections and keratitis have been reported. Rare cases of deep-seated (invasive) disease do occur in the immuno-compromised host.

Arthrographis species

Arthrographis species are a cosmopolitan mould isolated from soil and decaying vegetation. Two species of Arthrographis are most commonly isolated in the laboratory namely: A. cuboidea and A. kalrae, Arthrographis kalrae has been isolated from skin, nails, and respiratory sites, but has not been established as an etiologic agent of disease. Both species are considered to be allergenic. Toxic related disease has not been associated with this mould.

Aspergillus species

The genus Aspergillus is widely distributed in the environment, being identified in soil, on plants and decaying vegetation, in dust, on stored food, fruits, vegetables, feed products, wood chips, cotton, and in the air. The genus contains approximately 200 species and about 20 species of Aspergillus have been recognized as opportunistic pathogens. The most common of the opportunistic pathogens in this group is Aspergillus fumigatus.
A. fumigatus may be recovered from the indoor environment and is common in trash, house dust, and compost. A. fumigatus has worldwide distribution and grows over a wide range of temperatures. It is commonly recovered outdoors in compost piles, wood chips, soil, plants, seeds, and cotton. A. fumigatus is thermotolerant and is able to grow over a wide range of temperatures from below up to C. It flourishes in mild to warm soils and vegetable matter decomposing in warm environments, such as self-heating hay and composts. A. flavus grows on mouldy corn, peanuts, and other agricultural products. It can be found in soil, foods, and dairy products. Some strains produce a group of mycotoxins called aflatoxins.  Aspergillus niger is commonly found in the environment on textiles, in soils, grains, fruits, and vegetables. This species is considered common to indoor environments and usually displays a very musty odor. A. nidulans is widespread and primarily found in mild to warm soils and on slowly decaying plant material. It also can be found on potatoes, grain, citrus, and stored seeds of oats, wheat, corn, rice, and cotton. A. versicolor is a widely distributed fungus being detected in very cold regions, unlike most other species of aspergilli which prefer warmer regions. It may be commonly found in soil, hay, cotton, dairy products, dried cereals, nuts, and especially spices. This fungus is commonly recovered from buildings with humidity and ventilation problems.

Disease Associations:

Members of this genus cause a group of diseases known as aspergillosis. Aspergillus species are well-known to elicit three different clinical settings; namely, (1) allergic states; (2) toxicosis; (3) opportunistic infection. Most cases of aspergillosis are caused by Aspergillus fumigatus, however, A. flavus, A. niger, A. glaucus, A. nidulans, A. terreus, A. versicolor, A. clavatus, and A. ustus have been reported as causing disease. Aspergillus fumigatus is the second most common fungus in opportunistic mycoses following Candida albicans in the hospitalized patient. Aspergillus fumigatus is the most commonly encountered pathogen in the immunocompromised patient and is especially active as an allergic and invasive organism. Some strains of Aspergillus flavus produce a group of mycotoxins called aflatoxins. Aflatoxins are known animal carcinogens and there is limited evidence that this toxin may be a human carcinogen. It has been reported to cause occupational disease by inhalation. A. flavus has been associated with lung and disseminated aspergillosis. This fungus has also been reported as a cause of corneal, otomycosis, and naso-orbital infections. Aspergillus niger is a less common cause of invasive aspergillosis. It has been reported to cause skin and pulmonary disease. It is also a common cause of fungal otomycosis (ear infections).


Aureobasidium pullulans

Aureobasidium pullulans is a cosmopolitan fungus with its main habitat on the aerial parts of plants. Frequently isolated indoors in areas of free water such as condensate pans, flooded carpet, and other moist sites where water intrusion has occurred. It is a yeast-like fungus that generally becomes airborne through mechanical disruption of contaminated materials or by aspiration of contaminated water.

Disease Associations:

Aureobasidium pullulans does not cause primary human disease; however, high airborne levels have been associated with allergic reactions probably due to respiratory irritation. This fungus has been associated with human cases of keratitis, peritonitis, pulmonary disease, and invasive infection in an AIDS patient. No toxic diseases have been reported to date.

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Basidiomycetes

This class of organisms comprises one of the major taxon of true fungi. Basidiomycetes produce sexual spores called basidiospores at tips of tiny outgrowths from special cells called basidia. Many basidiomycetes also produce asexual spores called conidia, but in most cases these are not as conspicuous or numerous as in the Ascomycetes, and they do not seem to constitute a significant part of the air spora. These fungi include the mushrooms, bracket fungi, puff balls, and other macrofungi. Several genera (Lenzites, Merulius, Odontia, and Poria spp.) are known to cause dry rot. These decay fungi grow on and in wood and destroy the wood substances as they grow. Ingestion of a poisonous mushroom causes a disease entity known as mycotoxicosis. Some basidiospores can be identified by spore morphology on Air-O-Cell slides, but few if any grow on common laboratory agar media. Many basidiospores are reported to be allergenic.

Basidiobolus ranarum

This zygomycete has been isolated from decaying plants, soil, and from the fecal material of frogs, reptiles, fish, and bats. Its relationship to human occupied spaces suggests a common presence in the indoor environment, especially in tropical countries. This fungus rarely causes disease and no toxic effects have been documented to date. It has been reported in subcutaneous zygomycosis which involves predominantly the trunk and extremities, most often in children in tropical countries. This fungus rarely causes the disease entity rhinocerebral zygomycosis, typical of the other Mucorales (e.g., Rhizopus spp.).

Beauveria species

Beauveria species are ubiquitous in soil and plant debris with various species being parasites of insects. Beauveria bassiana is recognized as the etiologic agent of the devastating muscardine disease of silkworms. Beauveria species have been reported to cause mycotic keratitis and occasional pulmonary infection. These fungi should be considered allergenic, but no toxic diseases have been documented to date.


Bipolaris species

Bipolaris species are dematiaceous (pigmented) filamentous fungi that are widespread in nature and are most frequently associated with grasses, plant material, decaying food, and soil. Nearly all species of this genus are pathogenic to grasses, while some are common saprobes on dead plant material and in soil. Older obsolete names include Drechslera and Helminthosporium.

Disease Associations:

Bipolaris species are one of the causative agents of phaeohyphomycosis, particularly fungal sinusitis. The clinical spectrum is quite diverse, including allergic and chronic invasive sinusitis, keratitis, endophthalmitis, endocarditis, osteomyelitis, and fungemia as well as cutaneous and pulmonary infections and allergic bronchopulmonary disease. Bipolaris spicifera is the most commonly implicated Bipolaris species in human disease.

Blastoschizomyces capitatus

Blastoschizomyces capitatus (formerly called Trichosporon capitatus) may be isolated from environmental sources such as soil, beach sand, and as normal flora of the skin, respiratory, and digestive tracts of man. Although found in the environment, the largest study of the epidemiology of infection with this yeast-like fungus failed to reveal a common environmental exposure.

Disease Associations:

Invasive disease has been documented in immuno-compromised patients. With the increasing populations of immuno-compromised patients, infections due to this and other yeast species that were previously considered unusual are likely to become increasingly common. No toxic diseases have been documented to date.

Botrytis species

Botrytis species are parasitic on plants, vegetables, and soft fruits and has also been found in soil.
They are often recorded from regions of humid climate, both temperate and tropical. They are reported to be allergenic, but no cases of infections have been documented in humans.

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Candida species

Candida species have been isolated from a variety of environmental sources. Several Candida species, most notably C. albicans are ubiquitous human colonizers of the skin and mucous membranes in man. C. albicans has also been isolated from leaves, flowers, water, and soil, but the yeast generally does not become airborne. Other species of Candida have been isolated from mammals, birds, air samples, vegetation, juices, dairy products, grains, and insects.


Disease Associations:

Seven species in the genus Candida are well-known opportunistic human pathogens (C. albicans, C. glabrata, C. guilliermondii, C. krusei, C. lusitaniae, C. parapsilosis, C. tropicalis) and many others have been described as pathogens in individual case reports. Diseases caused by Candida species cover a diverse range of pathologic effects and are associated with many numerous underlying host factors that predispose persons to infections with Candida species. The most common infections include skin, nails, oral disease (thrush), and the genital tract of females. Candida infections of deep tissue are usually the result of hematogenous spread of the yeast from an endogenous site. Widely disseminated disease, usually with a fatal outcome if untreated, can occur in the immuno-compromised patient. No toxic diseases have been reported to date.

Chaetomium species

Chaetomium species are found in soil, air, and plant debris. Indoors they can be found on a variety of substrates containing cellulose including paper, textiles, plaster, and water damaged paper in sheetrock. Chaetomium species are ascomycetous fungi producing ascocarps called perithecia (contains sexual spores called ascospores). Chaetomium species may be recognized on spore trap slides by their characteristic ascospores.

Disease Associations:

Chaetomium atrobrunneum is a thermophilic and neutrotropic fungus and such makes this species a potentially dangerous fungal pathogen. Considered to be allergenic, but no toxic diseases have been reported. Chaetomium globosum is considered to be allergenic, but no toxic diseases have been documented to date. This fungus is the most common and widely distributed species of Chaetomium. This species is documented as an agent of onychomycosis (nail infection), peritonitis, and cutaneous lesions. Chaetomium strumarium is a common soil mould in warm areas on plant debris. It has been documented in fatal brain infections; however no toxic diseases have been documented to date.

Chrysosporium species

Chrysosporium is a genus of predominantly saprophytic moulds, and many species are isolated in soils associated with keratinous substrates such as shed hair or skin scales, fur, feathers, hooves, etc. Chrysosporium species usually have single-celled (rarely one- or two-septate) conidia; whereas species of dermatophytes (e.g., Trichophyton or Microsporum spp.) have or are capable of producing multi-celled conidia known as macroconidia.

Disease Associations:

A few species of Chrysosporium are closely related biologically to dermatophytes, even though they are normally nonpathogenic. Eight species occasionally occurring on humans have been identified. Chrysosporium species have been reported to cause disseminated disease and invasive sinusitis among immuno-compromised persons. Some geophilic species have been repeatedly isolated from onychomycosis (nails) and superficial infections. Toxic diseases have not been reported to date.

Cladophialophora species

Cladophialophora species are dematiaceous (dark pigmentation) fungi widely distributed in the soil and on plant debris. Unlike Cladosporium species, Cladophialophora species normally produce small conidia in long chains without shield cells or attachment scars.

Disease Associations:

Cladophialophora bantiana is the most common agent involved in cerebral phaeohyphomycosis. Because this disease usually infects immunocompetent individuals presumably by way of the respiratory tract, this mould should be handled with care in the laboratory. C. carrionii is usually associated with chromoblastomycosis, which is generally restricted to subtropical and tropical areas of the world. Most persons have long-term soil exposure with repeated trauma and tissue injuries to the feet and legs. C. boppii has been associated with skin lesions and may be a possible cause of chromblastomycosis. Toxic diseases have not been reported to date.

Cladosporium species

Cladosporium species are ubiquitous with worldwide distribution and are the most common mould on dead organic matter and in the air. In most parts of the world Cladosporium species are the most abundant genus isolated from air sampling. The outdoor numbers are reduced in the winter. The highest concentrations outdoors of Cladosporium species occur in summer and early fall in temperate areas. Cladosporium cladosporioides is the most common species on dead organic matter and in the air. Cladosporium species are common in indoor environments and often isolated from the surface of fiberglass duct liners around return and supply ducts, shower walls & curtains, and basement walls. They are usually found indoors in numbers less than outdoor numbers.

Disease Associations:

Although Cladosporium species are the most common of the fungi worldwide, they only rarely act as an opportunistic pathogen in humans. C. cladosporioides, C. sphaerospermum, C. elatum, and C. oxysporum have been reported as rare agents of phaeohyphomycosis. Cladosporium herbarum has been reported in cutaneous infection and keratitis. Studies have confirmed the importance of allergens of Cladosporium species as a cause of asthma, hay fever, and hypersensitivity pneumonitis (HP). No toxic diseases have been reported to date.

Conidiobolus species

As a member of the Class Zygomycetes, Conidiobolus species are found in decaying wood, plant debris, on insects, and in the G-I tract of lizards and toads in tropical areas. There are seasonal variations in the detection of Conidiobolus coronatus from soil with the greatest yield in September and October. C. coronatus most commonly causes a granulomatous disease involving nasal mucosa and subcutaneous maxillofacial tissues. These infections are rare, with only a few cases reported in the United States.

Cryptococcus species

The genus Cryptococcus includes oval to round yeasts that reproduce by multilateral budding and are anamorphs of the jelly fungi and smuts of the Basidiomycetes. Cryptococcus spp. (not C. neoformans) can be recovered from man, mammals, soil, air, wine, leaves, and water.

Cryptococcus neoformans

Of the more than 34 species of the genus Cryptococcus, Cryptococcus neoformans is the only one considered pathogenic to humans and causes the disease cryptococcosis. Three main varieties have been recognized, namely var. neoformans, var. gattii, and var. grubii, on the basis of their different life cycles, physiology, ecology, and genetics. C. neoformans var. gatti is detected in tropical and subtropical climates associated with Eucalyptus trees, whereas var. neoformans is found worldwide and is associated with pigeon droppings and soil contaminated with avian excreta. According to recent studies, the environmental habitat of var. neoformans appears to also be related to trees and plant material as it is for var. gattii. Pigeon droppings only continue the propagation of the fungus, providing an enriched media for growth and dispersion. In fresh or wet pigeon droppings, var. neoformans yeast cells are somewhat inhibited, which in contrast are highly resistant in dry excreta. Avian excreta are likely to be positive for C. neoformans in sheltered environmental sites than in those exposed to sunlight because of the high susceptibility of this fungus to UV light.

Disease Associations:

C. neoformans causes infections in animals and humans throughout the world. The fungus may infect normally healthy persons, but usually causes disease in the immunocompromised host. C. neoformans commonly occurs in the environment of urban areas, and even though human exposure to the fungus appears to be a common event, cryptococcosis remains a sporadic disease. Human to human and animal to human natural transmission has never been reported and nosocomial infections have not been described. Normal hosts are rarely reported to be infected with C. neoformans var. neoformans. However, normal or immunocompetent persons may develop cryptococcosis due to var. gattii in those countries where this variety is endemic. The most commonly encountered predisposing factor for development of cryptococcosis is AIDS. Less commonly, cancer patients receiving chemotherapeutics or long-term corticosteroid treatment, and organ transplant recipients may also develop cryptococcosis. C. neoformans var. grubii has a worldwide distribution and is an inhalation-mycosis occurring almost exclusively in patients with impaired T-cell function such as Hodgkins disease.

Cunninghamella species

Cunninghamella species are zygomycete fungi with a wide distribution in decaying vegetation and animal matter, in the soil, and recovered from foodstuffs and fruit. These fungi have been mainly found in Mediterranean or subtropical climatic zones. These fungi are thermotolerant and are able to grow at temperatures above C. C. bertholletiae is known as an occasional agent of zygomycosis causing pneumonia in immunocompromised children, disseminated disease in renal and liver transplant recipients, and infections in AIDS patients.

Curvularia species

Curvularia species are known to have a wide distribution, mostly occurring on dead plant material. Curvularia species are particularly common as a saprophyte or weak pathogen causing leaf spots, seedling blight, and seed germination failure. These fungi produce darkly pigmented (dematiaceous) brown to black hairy colonies on an agar plate. The mould is recognized microscopically by uniquely shaped multiseptate conidia that are usually curved as the result of an enlarged central cell, which is also darker than the other surrounding cells.

Disease Associations:

Curvularia species are among the important causes of fungal keratitis, sinusitis, and cutaneous infections by traumatic implantation. They are also has been reported as agents of phaeohypho- mycosis causing mycetoma and subcutaneous and systemic disease, with most infections occurring in the immunocompromised host.

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Drechslera species

Drechslera species are cosmopolitan fungus isolated from soil and plant material, particularly grasses. Some species are plant pathogens. Microscopically they may be confused with Bipolaris spp. or Exserohilum spp. Although D. biseptata has been shown to have pathogenic potential, most reports of disease caused by Drechslera species represent either misidentification or fungi that have since been reclassified as Bipolaris or Exserohilum species (Anaissie, McGinnis, & Pfaller, Clinical Mycology, 2003).

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Engyodontium album

Engyodontium album can be commonly detected in waste and moist material and frequently isolated from paper, jute, linen, and painted walls. This fungus must be microscopically distinguished from Beauveria and Tritirachium spp. The mould has been reported to cause keratitis, brain abscess, and endocarditis.

Epicoccum species

Epicoccum species are dematiaceous mould that has widespread distribution being isolated from air, animals, foodstuffs, and textiles. They are common early secondary invaders of numerous plants causing leaf spots. Epicoccum species are allergenic fungus, but not documented as an etiologic agent in human or animal disease.

Exophiala species

Exophiala species are cosmopolitan fungi being isolated from decaying wood, soil, and surfaces in contact with cool, fresh water. Exophiala species are the main genus of black yeasts. Most species are olivaceous to black and initially yeast-like, later becoming velvety with the production of aerial hyphae. Some species of Exophiala are entirely yeast-like on culture in the laboratory. The pleomorphic nature of Exophiala species and their intraspecies variations make identification and differentiation difficult. Phaeoannellomyces werneckii is another current name for Exophiala werneckii.

Disease Associations:

Only a small number of the described Exophiala species have been reported to cause human infections. E. jeanselmei is the most common agent of phaeohyphomycotic cysts and subcutaneous lesions and the species also causes mycetoma and chromoblastomycosis. Some of the other species of Exophiala are known to be agents of phaeohyphomycosis.

Exserohilum species

Exserohilum species are cosmopolitan dematiaceous fungi commonly found as a plant pathogen mainly on grasses, many other plants, and in the soil. Exserohilum species are distinguished from Bipolaris and Drechslera by their conidia with a protuberant hilum. Human mycoses usually involve cases of sinusitis, eventually with cerebral involvement. Some cases of subcutaneous or deep phaeohyphomycosis have been reported in humans and animals.

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Fusarium species

The genus Fusarium are widespread as a common soil saprophyte and are an important plant pathogen. Some species produce toxins in grains or stored animal feed. On culture media, this rapidly growing fungus appears in pink, yellow, red, or purple shades. Fusarium species are usually identified by their characteristic multicellular sickle-shaped macroconidia, but identification may be difficult with some species.

Disease Associations:

Fusarium species causes a wide spectrum of human disease, including mycotoxicosis and infections which may be superficial, invasive, or disseminated. Fusarium species frequently occur as agents of various kinds of hyalohyphomycosis after traumatic inoculation. Fusarium may cause localized infections of the cornea, skin, and nails in the immunocompetent host. In severely immunocompromised patients, Fusarium has recently emerged as a significant cause of morbidity and mortality and is the second most common pathogenic mould (after Aspergillus) in high risk patients with hematologic cancer and in recipients of solid organ transplantation or allogeneic bone marrow transplantation (BMT).

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Geotrichum species

Geotrichum species are ubiquitous fungus with worldwide distribution occurring in soil, air, water, sewage, various plants, cereals, dairy products, fruits, and is present as normal flora of the upper respiratory tract of man. Geotrichosis is generally an infection of the bronchi, lungs, and mucosa caused by the yeast-like fungus, Geotrichum candidum. In the mouth it can produce thrushlike lesions.

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Hormonema dematioides

Hormonema dematioides is a black yeast-like fungus recognized as an opportunistic pathogen of conifers and possibly other plants. It is often found in moist environments indoors. It must be distinguished from the black yeast-like fungus, Aureobasidium pullulans. This fungus has been reported as a rare cause of cutaneous phaeohyphomycosis and fungal peritonitis.

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Lecythophora species

Lecythophora species are yeast-like fungi that have widespread distribution occurring in decaying vegetation and in the soil. They are associated with moist environments and have been isolated from rotten wood and foodstuffs. L. hoffmannii has been reported to cause subcutaneous abscess and keratitis. Fungal sinusitis has been described in AIDS patients. L. mutabilis has been reported to cause peritonitis, endocarditis, and keratitis.

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Memnoniella species

Memnoniella species have world wide distribution and have been isolated from soil, paper, wallpaper, textiles, and decaying plant material. They are associated with moist environments and are indicative of wet, damp, or water related conditions. They are known to produce toxic metabolites similar to that produced by Stachybotrys chartarum.

Mucor species

Mucor species, members of the order Mucorales, have world wide distribution and are found in decaying vegetables, foodstuffs, fruits, soil, and animal excreta. Mucor species are rapidly growing fungi on laboratory agar media and are distinguished from Rhizopus species by their lack of formation of rhizoids.

Disease Associations:

Zygomycoses (which includes Absidia, Mucor, Rhizopus, etc.) are rare in healthy individuals, unless trauma has provided a portal of entry into the body for the fungus. Mucor species are rare causes of disseminated disease, but the fungus has been recovered from cutaneous lesions, endocarditis, and arthritis. Rhinocerebral disease has also been described with Mucor species.

Myxomycetes

Myxomycetes are a class of viscous or mucilaginous fungi, also called slime moulds. These organisms have affinities to both animals and fungi. The plasmodial (amoeboid) feeding stage shows animal-like characteristics. They have no cell wall and actively engulf organic matter and bacteria in the environment. The reproductive stage, however, places the slime moulds with fungi, since spores are produced within fruiting bodies. These spores are well adapted for wind dispersal and have been identified in air samples. They have been reported to be allergenic to sensitized persons.

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Nigrospora species

Nigrospora species have a widespread distribution in decaying plant material, the soil, and air. Nigrospora species are distinguished from Humicola species by very black, opaque, conidia borne on hyaline, inflated conidiophores. They have not been documented as an etiologic agent of disease, but has been reported from a lesion in a leukemic patient and as a probable cause of keratitis.

Paecilomyces species

Most species of Paecilomyces are commonly isolated worldwide from soil and decaying plant material and are often implicated in decay of food products and cosmetics. Some species are able to tolerate high temperatures; thus are inhabitants of compost piles. P. variotii is able to produce significant mycotoxins such as patulin and viriditoxin.

Disease Associations:

The two most commonly isolated species of Paecilomyces: P. lilacinus and P. variotii are rarely pathogenic to humans. However, P. lilacinus is being reported with increasing frequency and is now considered an emerging fungal pathogen. In immunocompetent persons, Paecilomyces species have been implicated as etiologic agents of keratitis associated with corneal implants, endophthalmitis, endocarditis following valve replacement, sinusitis, peritonitis in dialysis patients, and cutaneous infections. Disseminated infection, pneumonia, cellulitis, and kidney infection have also been reported in immunocompromised patients. Recent outbreaks of P. lilacinus in cutaneous infections have been reported in neutropenic patients and deep seated infections in bone marrow transplant recipients have also been traced to contaminated hand lotion solutions.

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Penicillium species

Penicillium species are very large and ubiquitous genus with worldwide distribution over a broad range of climates in soil, decaying vegetation, and foods. They are the most abundant genus of mesophilic fungi in temperate soils. About 200 species have been identified. Their role in these habitats is to act as decay fungi; they are important agents in the natural processes of recycling used biological material. Penicillium species are indoor contaminants commonly found in carpet, wallpaper, and inside fiberglass duct insulation. High viable or spore trap air counts may be detected where water damaged materials such as drywall, wallpaper, wood, and wood products are present.

Disease Associations:

Penicillium marneffei is the only Penicillium species to cause important human disease in immunocompetent individuals. The dimorphic mould is restricted to Asia (Southeast and Far East) where it is considered an indicator of AIDS. This mould may cause hypersensitivity pneumonitis, allergic alveolitis in susceptible individuals. Penicillium species other than P. marneffei rarely cause disease even among the immunocompromised hosts. Many species of Penicillium produce mycotoxins. In recent years the role of Penicillium species in indoor air quality has been established as a cause of allergenic reactions in some persons.

Phaeoannellomyces werneckii

Phaeoannellomyces werneckii (Exophiala werneckii) causes tinea nigra, a superficial cutaneous fungal infection typically involving the palm of the hand or soles of the feet. The fungus is differentiated from other dematiaceous moulds by its salt tolerance, lack of growth at C, and the wide densely septate, thick-walled brown hyphae.

The infection is endemic in tropical and subtropical coastal regions in the Caribbean, Central and South America, Asia, and Africa. Cases have been reported from southeastern U.S. coastal states and Europe. Most infections are usually acquired in subtropical coastal locations. Being a salt-tolerant organism, infection is postulated to occur through exposure of superficially abraded skin to drying tidal pools. Children and young adults are most frequently affected, and most infections are reported from non-immunocompromised persons.

Phialophora species

Phialophora species are dematiaceous (pigmented) mould found in decaying wood, wood pulp, and in the soil. These fungi are distinguished from Exophiala by having distinct collarettes and absence of yeast cells. Phialophora species have been implicated as causes of all of the disease classes caused by dematiaceous fungi: chromoblastomycosis, mycetoma, and phaeohyphomycosis. P. verrucosa is the second most common cause of chromoblastomycosis worldwide and the most common cause in North America.

Phoma species

Phoma species have worldwide distribution; commonly found in the soil and are considered plant pathogens (particularly in potatoes). Some species of Phoma may produce pink or purple spots on painted walls due to their pigment production. Phoma species have been reported predominantly in cutaneous infections, but overall these fungi are rarely isolated from humans. This mould is reported to be allergenic in susceptible individuals.

Pithomyces species

The cosmopolitan fungus Pithomyces is often found in decaying wood, plant material, and the soil. A dematiaceous fungus that is distinguished from Alternaria and Ulocladium species by its scarcely differentiated conidiophores and its conidia which retain an annular frill at the base upon liberation. This fungus has not been documented as an etiologic agent of disease; however, it has been reported in cutaneous lesions in immunocompromised patients.

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Rhizopus species

Rhizopus species are ubiquitous fungi commonly found in the soil. They have been isolated from decaying fruit and vegetables, compost, old bread, and cereals. Some species are plant pathogens. A member of the Order Mucorales of the Zygomycetes, Rhizopus species are rapidly growing fungi on laboratory media and are distinguished from Mucor by its formation of rhizoids (root-like structures). The spores of Rhizopus may become easily airborne by the slightest disruption of the colony on an agar plate or from building materials.

Disease Associations:

The major clinical settings for disease (Zygomycosis) with Rhizopus species are rhinocerebral and pulmonary, due to the inhalation of spores and subsequent dissemination from the respiratory tract. A primary predisposing factor is poorly controlled diabetes mellitus, especially when ketoacidosis is present. Nosocomial infections have resulted from aerosol contamination of air-conditioning systems and wound dressings. R. arrhizus is the most frequent agent of rhinocerebral zygomycosis and R. microsporus var. rhizopodiformis accounts for 10% to 15% of human zygomycotic disease, primarily cutaneous and gastrointestinal infections. Zygomycoses are rare in healthy individuals, unless traumatic implantation (e.g., wounds) has allowed a portal of entry for the fungus.

Rhodotorula species

Rhodotorula species can be isolated from a variety of environmental sources. These include soil, air, water, cooling coils, drain pans, plants, dairy products, fruit juices, shower curtains, and toothbrushes. These fungi have also been isolated from human skin, urine, stool, and respiratory secretions. Rhodotorula is a genus of yeast-like fungi that produces carotenoid pigments ranging from a yellowish to red that can be observed with individual colonies on laboratory media.

Disease Associations:

Confirmed cases of human infection are rare. Humans may be colonized with Rhodotorula, but it is usually transient. The most commonly reported infection due to Rhodotorula is fungemia. Rhodotorula fungemia most commonly occurs in patients with central venous catheters. There are also reports, however, of endocarditis, meningitis, peritonitis, and eye infections especially in the high risk patient (e.g., immunosuppressed). This yeast has been reported to be allergenic.

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Scedosporium species

Scedosporium apiospermum (teleomorph or sexual name – Pseudallescheria boydii) has worldwide distribution being commonly isolated from rural soils, sewage and contaminated water, and from the manure of farm animals. Scedosporium prolificans has been isolated from samples of soil.

Disease Associations:

Two forms of disease have been described: invasive disease caused by both Scedosporium species and mycetoma caused only by Pseudallescheria boydii. As an emerging opportunist, serious infections by P. boydii have increased in the last few years among patients with hematologic disease, particularly those recipients undergoing bone marrow transplant. Scedosporium prolificans can be introduced traumatically into persons via thorns or splinters; and thus may be frequently isolated from cutaneous and subcutaneous lesions. Since 1990 more cases of disseminated disease in immunocompromised patients are being reported.

Scopulariopsis species

The most common species of this group is S. brevicaulis with worldwide distribution in soils, plants, feathers, and insects. S. brumptii is a common soil fungus and has been isolated from a variety of materials including house dust. Scopulariopsis species are distinguished from Penicillium species by their formation of pyriform conidia, typically with a truncated base. S. brevicaulis rarely causes human infection, but cases of onychomycosis (nail), skin lesions, and opportunistic invasive disease in the immunocompromised hosts have been reported. S. brumptii has caused pulmonary hypersensitivity and possible mycetoma of a foot.

Sporidiobolus species

Sporidiobolus species (Sporobolomyces is the anamorph name) are basidiomycetous yeasts being characterized by carotenoid pigments observed in culture ranging from pink to red or orange. These yeasts may be recovered from soil, from air, and from other environmental sources such as leaves, bark, grasses, and fruit. Only rarely a cause of clinical disease in humans, S. salmonicolor has been reported in several instances of disease involving asthma, dermatitis, extrinsic allergic alveolitis, lymphadenitis, and bone marrow involvement in AIDS patients.

Sepedonium species

Sepedonium species are cosmopolitan mould that are found in soil as a saprobe and are known to parasitize certain mushrooms. No cases of infection have been reported in humans or animals to date.

Sporotrichum species

Sporotrichum species have widespread distribution occurring in decaying wood and in the soil. Sporotrichum species are the anamorphs (asexual stage) of basidiomycetous fungi which are important agents of wood decay. S. pruinosum appears to be potentially pathogenic in the respiratory tract since a few cases of repeated isolations from respiratory secretions are suggestive of bronchopulmonary colonization.

Sporothrix species

Sporotrichosis is caused by the soil dimorphic fungus Sporothrix schenckii. It is usually a chronic infection of the skin and subcutaneous tissue. Sporotrichosis is global in distribution but is found primarily in temperate zones of North America, South America, and Japan. Infection usually occurs by direct skin inoculation from contaminated soil or thorned plants such as roses. Outbreaks of infection have been associated with contaminated plant material such as straw, wood, hay bales, and sphagnum moss. Most cases are associated with vocational or recreational exposures. Sporothrix cyanescens (a saprophytic species) has been implicated in one case of sporotrichosis in an immunocompromised patient.

Stachybotrys species

Stachybotrys species are cosmopolitan, saprophytic fungi with worldwide distribution and can be found on paper, seed, in soil, textiles, decaying plant material, and other cellulose rich materials. Major indoor habitats include water-damaged wallpapers and jute carpet backing, carpet glues, ceiling tile, water-soaked wood, wall paneling, gypsum board, plus moist debris in ducts and damp papers and books. Stachybotrys species will not grow on vinyl, plastic and concrete products or ceramic tiles. They are slow growing mould on laboratory media and do not compete well with other rapidly growing fungi. They may be readily found in most buildings that have experienced chronic water problems that are left unattended. The spores of Stachybotrys are not readily airborne therefore, bulk or swab sampling can be important for detecting the fungus indoors.

Disease Associations:

Stachybotrys species are known to produce secondary metabolites called mycotoxins that, when ingested, inhaled, or come in contact with skin are harmful to animals and humans. Mycotoxins generally have low volatility; therefore, inhalation of volatile mycotoxins is not likely to occur. The mycotoxins, however, are integral part of the fungus (e.g. spores, hyphal fragments). It has been known for a long time that animals consuming Stachybotrys contaminated hay have experienced acute manifestations characterized by a variety of neurologic signs, such as tremors, incoordination, and impaired or loss of vision. Other chronic manifestations such as dermonecrosis, leucopenia, gastrointestinal ulceration, and hemorrhage have also been noted.
Although mycotoxins (specifically macrocyclic trichothecenes) were isolated from the contaminated hay in the human and animal intoxications, current illnesses in humans occupying Stachybotrys-contaminated buildings are not yet proven to be related to these toxic products.

Recently, two researchers presented a study in Brescia, Italy, at the Eighth International Symposium on Neurobehavioral Methods and Effects in Occupational and Environmental Health (June 2002) outlining 43 sick buildings with 105 patients (Ritchie Shoemaker, M.D., of the Center for Research on Biotoxin Associated Illnesses in Pocomoke City, MD). Dr. Shoemaker has stated: “We have terrific documentation that a number of people working in a mold-contaminated building experienced similar illnesses, response to treatment, and relapse to re-exposure”.

Syncephalastrum species

Syncephalastrum species belong to the Order Mucorales of the Zygomycetes. These fungi are commonly isolated from animal dung and soil in tropical and subtropical countries. The fruiting structures may superficially resemble and are often mistaken for those seen in the aspergilli. These fungi are very rarely associated with human disease but have been reported in cutaneous infections.

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Trichoderma species

Trichoderma species have widespread distribution and are commonly found in soil, wood, fallen timbers, decaying vegetation, pine needles, and paper. They are known to readily degrade cellulose. Indoors, the mould may be isolated on paper tapestry in kitchens, unglazed ceramic surfaces, house dust, and stored grains. Trichoderma viride is an emerging pathogen in the immunocompromised host with underlying diseases such as leukemia, organ transplants, chronic lung disease, chronic renal disease, and in patients undergoing continuous peritoneal dialysis. This fungus may cause Type 1 allergy inhalation in the sensitized individual and is known to produce potent metabolites (e.g., mycotoxins).

Trichosporon species

Trichosporon species are yeast-like fungi that may be isolated from soil, water, vegetables, mammals and birds. They can also be isolated in the mouth, on the skin and nails of humans. They are generally associated with water intrusion in the indoor environment. There have been 17 named species reported and about six have been associated with human disease. Among the species most often reported to cause human disease is Trichosporon beigeli. Superficial infections include infection of the hair shaft (called white piedra), and less commonly, onychomycosis (nails). Deep-seated infections may be either localized or disseminated. Disseminated disease has been reported in patients with hematologic malignancies, burns, and organ transplants.

Tritirachium species

Tritirachium species are widespread in decaying vegetation and in the soil. They are an insect pathogen. The mould must be differentiated from Beauveria and Engyodontium album. This fungus has been reported to cause corneal ulcers and a case of otomycosis. They have also been isolated from a catheter tip.

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Ulocladium species

Ulocladium species are cosmopolitan fungus commonly found in the soil and on decaying herbaceous plants, paper, textiles, and wood. A dematiaceous (darkly pigmented) fungus that produces muriform conidia having septa in more than one plane. The fungi in this group include Alternaria, Stemphylium, Pithomyces, Ulocladium, and Epicoccum species. Only Alternaria has been convincingly involved in human disease. Although Ulocladium species are common contaminant, their presence indoors may indicate moisture intrusion. If given the right circumstances, Ulocladium species may cause opportunistic infection. They have been reported in subcutaneous infections.

Ustilago species

Ustilago species are yeast-like fungi found as a major pathogen of plants and in the air. These basidiomycetous fungi have been isolated from sputum and body fluids, but their association in disease is unclear.

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Glossary of Fungal Diseases

Aspergillosis: a wide range of human and animal diseases caused by several species of Aspergillus, particularly Aspergillus fumigatus. The most predominant form of Aspergillosis is pulmonary and over 95% of all infections are caused by three species: (A. fumigatus, A. flavus, A. niger).

Chromoblastomycosis: a chronic, subcutaneous, granulomatous mycosis of man and higher animals caused by implantation in the skin of several dematiaceous (pigmented) fungi from exogenous sources (wood, soil, plant debris). The infection is usually distinguished by the unique finding of muriform “sclerotic bodies” in material from lesions. The traditionally recognized dematiaceous agents of chromoblastomycosis are: Fonsecaea pedrosoi (most common), Fonsecaea compacta, Cladophialophora carrionii, Phialophora verrucosa, and Rhinocladiella aquaspersa. Recent reports have implicated infections with Exophiala jeanselmei and Exophiala spinifera.
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Endophthalmitis: an infection of the intraocular tissues of the eye and is usually associated with injury to the eye by instruments, fluids, and foreign materials during ocular surgery (exogenous contamination). Endogenous contamination of the eye may be the result of hematologic seeding but can also result from direct extension of an infectious process such as keratitis with intraocular extension.

Hyalohyphomycoses: caused by a group of heterogeneous fungi with only hyaline hyphae (without pigment in the wall) that may include only localized infection (usually following traumatic implantation) whereas disseminated disease tends to occur among immunosuppressed persons. A number of fungi causing this disease are increasing and the most common ones include Fusarium, Penicillium, Scedosporium, Acremonium, and Paecilomyces species.

Keratitis: an inflammation of the cornea. Mycotic keratitis may be potentially a serious fungal infection of the cornea and based on numerous reports fungi have been found to cause 6%-53% of cases of ulcerative keratitis. More than 70 species of fungi have been reported to cause mycotic keratitis.

Mycetoma: a chronic subcutaneous infection caused by actinomycetes or fungi. It is characterized by the formation of abscesses, which contain aggregates of fungal or actinomycete filaments known as grains. Mycetoma has numerous causes, with more than 20 species of fungi (eumycotic) or actinomycetes (bacteria) being commonly involved. The main agents of actinomycotic mycetoma include Streptomyces, Actinomadura, and Nocardia brasiliensis (the most common actinomycete). The fungi include Madurella mycetomatis (the most common fungus), Madurella grisea, Leptosphaeria senegalensis, Scedosporium apiospermum, and species of Fusarium, Acremonium, and Aspergillus.

Onychomycosis: infection of the nails and seen mainly in adults. The toenails are more commonly infected than the fingernails. The most common cause is the dermatophyte, Trichophyton rubrum. Other nondermatophyte fungi may cause onychomycosis such as Candida species, Scopulariopsis brevicaulis, Scytalidium, Aspergillus, Pyrenochaeta, and Chaetomium species.

Otomycosis: infections of the external auditory canal and caused by Candida species, Aspergillus species, particularly Aspergillus niger, and a variety of other fungi. An aggressive form of external otitis noted in immunocompromised patients, malignant otitis externa, which may be caused by fungi, particularly Aspergillus species.

Phaeohyphomycosis:

includes infections caused by all agents appearing in tissue as dematiaceous (pigmented) yeast cells, pseudohyphae-like elements, septate hyphae, or any combination of these forms (McGinnis & colleagues). The number of fungi implicated as etiologic agents includes at least 104 different species from 57 genera. Phaeohyphomycosis has been divided into four disease categories (Fader and McGinnis): superficial, cutaneous and corneal, subcutaneous, and systemic.

Zygomycosis: comprises various types of infections caused by zygomycetes. The disease has often been referred to be caused by members of the order Mucorales (Mucormycosis). There are several distinct forms of the disease which include rhinocerebral, pulmonary, cutaneous, and disseminated mycosis. The most often implicated mould in zygomycosis is Rhizopus species. Other zygomycetes such as Mucor, Apophysomyces, Saksenaea, Cokeromyces, Basidiobolus, and Conidiobolus species have also been reported to cause disease.

References for Identification of Fungi

• Guide to Clinically Significant Fungi: Sutton DA, Fothergill AW, Rinaldi MG, 1998.

• Identifying Filamentous Fungi: “A Clinical Laboratory Handbook”, St-Germain G, Summerbell R, 1996.

• Pictorial Atlas of Soil & Seed Fungi: 2nd Edition, Watanabe T, 2002.

• Introduction to Food and Airborne Fungi: 6th Edition, Samson RA, Hoekstra ES, Frisvad JC, Filtenborg O, 2000.

• Medically Important Fungi: “A Guide to Identification”, 4th Edition, Larone DH, ASM Press 2002.

• Atlas of Clinical Fungi: 2nd Edition, de Hoog GS, Guarro JG, Figueras, MJ, 2000.

• The Genera of Hyphomycetes from Soil: Barron,1972.

• Identification Manual for Fungi from Utility Poles in the Eastern US: Wang CJK, Zabel RA, 1990.

• Laboratory Handbook of Dermatophytes: Kane J, Summerbell R, Sigler L, Krajden S, Land G, 1997.

• Manual of Clinical Microbiology: 8th Edition. Patrick Murray, Ellen Jo Baron, James Jorgensen, Michael A. Pfaller, Robert H. Yolken. ASM Press, Washington, DC, 2003.

• Anaisse, EJ, McGinnis MR, Pfaller MA: Clinical Mycology, 2003.

• Manual of Environmental Microbiology: 2nd Edition, Hurst CJ, Crawford RL, Knudsen GR, McInerney MJ, and Stetzenbach LD, ASM Press, Washington, DC, 2002.