Microbial Investigation 

Post Remediation

Indoor Air

Allergen and Asthma

COMMON INDOOR MOLD SPORES



Alternaria are fungal organisms very commonly isolated from outdoor air samples (seasonally varied in late summer with a worldwide distribution) and are found in association with house dust, acrylic paint, foodstuffs, decaying plant material, seeds, soils, textiles, water damaged building materials, window caulking and wood.  There are close to fifty species of this genus, which are generally known to cause plant diseases by hosting specific plant parasites.

Amerospore: a non-filamentous, 1-celled spore, with a length to width ration of <15:1 and with no projections longer than ¼ of the spore’s body length. Amerospores do not include strongly curved spores or very long spores.

Ascospores are a general category of spores that have been produced by means of sexual reproduction (in a sack-like structure called an ascus). These are ubiquitous saprobes and plant pathogens, many of which are easily identifiable (i.e.Chaetomium). This group contains potential opportunistic pathogens, toxin producers, and allergens depending on the genus and species. A rupture in the top portion of the ascus disperses the spores during rain or in times of high humidity. The presence of ascospores in indoor air samples normally indicates infiltration of outdoor air.

Aspergillus/Penicillium spp. – Both Aspergillus and Penicilliumare fairly common in the indoor environment. They are commonly present in higher levels indoors when compared to outdoors conditions. Increased levels of these spores indoors usually indicate a water intrusion/leak and/or elevated moisture conditions. Aspergillus/Penicillium spp. are very common worldwide. They can be isolated from air, plants, foodstuffs, soil, dust layers, garbage/compost, animal dung, cotton, cellulose, textiles, carpet, wallpaper, and in interior fiberglass duct insulation, painted surfaces, wood and fabric covered furnitureand cotton fabrics. Some Aspergillus species are allergenic and other species produce powerful mycotoxins. Some of the species are one of the most common causes of systemic fungal disease in humans and animals causing primarily acute or chronic respiratory tract infections. All of the species contained in this genus should be considered allergenic. Some Penicillium species produce a mycotoxin. The Aspergillus/Penicillium spp. group represents fungal spores from a variety of fungal genera that can be indistinguishable from other similarly small, round (globose to sub-globose) fungal spores including, but not limited to the fungal genera; Acremonium, Botrytis, Gliocladium, Paeciliomyces, Trichoderma, Scopulariopsis, Wallemia, and many others.

Aureobasidium is a yeast-like fungus, which is commonly found on the silicon caulk used in bathrooms and kitchens, on damp window frames, and in shower tracks. Aureobasidium produces two types of spores. While one type of spores are small and hyaline, the other type of spores are pigmented and larger.

Basidiospores are a general category of sexual spores that have been released from the basidium of a fungus. This class contains the mushrooms, shelf fungi, puffballs, and a variety of other macro fungi. A ubiquitous type I & III allergen, saprobe and plant pathogen, mainly found in gardens, forests, and woodlands. Spores disseminate during rain or in times of high humidity. Rarely opportunistic pathogens, many basidiomycete spores are reported to be allergenic. Basidiospores are an agent of dry wood rot, which may destroy the structure wood of buildings. The presence of Basidiospores in indoor air samples usually indicates an infiltration of outdoor air.

Bipolaris/Drechslera includes two genera that produce spores with a similar morphology. These spores are abundant in the outdoor environment. Occasionally, they can also grow indoors on a variety of materials but they require moderate water activity levels to grow. Therefore, they are not normally the primary colonizers of building materials after a moisture intrusion event.  

The genus Chaetomium is composed of approximately 160 – 180 different species with a worldwide distribution and is a cellulose decomposer frequently isolated from air, cotton, wood, fiberglass insulation, air filters, decaying plant material and soils.  It can be readily found on the damp or water damaged paper in sheetrock. It is commonly identified on water damaged wood.

Cladosporium is the most frequently found genus of fungi in outdoor air in temperate climates and the enzymes are especially suited for the breakdown of cellulose, pectin and lignin.  There are more than 500 species that are found in both indoor and outdoor environments with an optimum growth rate at a temperature range of 18-28°C.  Most colonies of Cladosporium spp. from typical indoor air samples are of outdoor origin.  This is primarily due to their ability to rapidly invade many different habitats and easily disperse large numbers of spores.  Studies have shown that as many as 10,000 spores / m3 of Cladosporium spp. can be found in an outdoor sample in the summer.  Cladosporium is isolated from air, dust, plants (decaying or alive), soil, textiles and wood. Cladosporium is also often encountered in dirty refrigerators, on moist window frames and anywhere condensation can occur (such isolation is not normally a cause for concern).  There are no specific mycotoxins that are known to be produced by species ofCladosporium spp.

The genus Curvularia contains some 35 species which are facultative saprophytic pathogens of tropical or subtropical plants, but a few are commonly isolated in temperate agricultural areas. The spores of the Genus are readily distinguishable by their 4-septae, ellipsoidal, curved spores that contain a central cell that is the largest.

Epicoccum are common indoor and outdoor airborne flora (there are approximately 60 species), which have a worldwide distribution.  These molds are considered secondary invaders and are commonly isolated from many substrates such as air, dust, human skin & sputum, paper products, plants (decaying or alive), soil and textiles.  No specific mycotoxins have been reported for this fungus.

Fusarium is a common soil fungus found on a wide range of plants. It is often found in humidifiers. Several species in this genus can produce potent trichothecene toxins on grains during unusually damp growing conditions. Symptoms may occur either through ingestion of contaminated grains or possibly inhalation of spores. Reported to be allergenic, it is frequently involved in eye, skin and nail infections.

Ganoderma is classified as a bracket fungus. The spores have an orange inner wall and spines that penetrate a colorless outer wall (double walled). They produce bracket or conk mushrooms on trees. Their basidiospores are very common in outdoor air during season.

Geotrichum is found in the mouth, skin and gastrointestinal tract of normal humans.  This species is also isolated from citrus fruit, compost, dairy products, digested sludge (sewage), sandy loam and soil.  Geotrichum is associated with strong pungent odors.

Hyphal fragments are the vegetative, filamentous structure from the fungal growth. It presence possibly indicates presence and growth of fungi. It is unusual for hyphal fragments to become airborne unless it is disturbed. Elevated levels of hyphal fragments indoors may suggest indoor fungal growth and disturbance.

Mucor/Rhizopus is a group of rapid growing fungi that often appear in sampling from areas of high moisture and/or relative humidity within soil.  Both species have a worldwide distribution and heavy exposure to spores may cause allergic reactions.  There are more than fifty species of Mucor that are commonly found in agricultural settings; compost, hay, manure, plant material and specifically soil.  It is one of the most common molds isolated from house dust; found in dirty carpets, indoor air and ventilation ducts.  Rhizopus is a common organism and facultative parasite of mature fruits and vegetables.  Rhizopus species are frequently isolated from house dust, wood pulp, dung, nuts and seeds.

Mitospores: Fission and budding are methods of asexual reproduction in a number of fungi, the majority reproduce asexually by the formation of spores. Spores that are produced asexually are often termed mitospores, and such spores are produced in a variety of ways.

Nigrospora:  Spores of Nigrospora are very characteristic. Species of Nigrospora grow on a variety of plants. They grow on water-damaged materials in a few occasions.

Paecilomyces has a worldwide distribution and is commonly isolated from air and dust (especially in warmer climates).  This rapid growing, large group of under studied fungi is closely related to Penicillium and can be found in a wide variety of outdoor substrates (that can generate heat) such as compost material, plant leaves, roots, soil, polluted water and wood.  It is also associated with water-damaged buildings, carpets, drywall, fiberglass material, paper products, PVC piping, humidifier water, house dust and wood substrates.  This species can also be associated with foodstuffs and decomposition of organic materials.

Pithomyces grows on decaying wood, soil, and plant materials. It rarely grows indoors. The presence of these spores in indoor samples normally indicates infiltration of outdoor air. It produces large, dark-pigmented, oblong or barrel-shaped, septated spores.

Rusts are a group of almost 5,000 specialized plant parasites. Although morphologically simple, some rusts have the most complex life cycle found in the fungi, in addition to possessing a high degree of host specificity. Their presence indoors is usually an indication of outdoor air infiltration.

Smuts: The members of this order can produce a yeast-like unicellular stage. The vast majority of the members of Ustilaginales are serious plant parasites. These fungi are called smut fungi and number around 850 species which form dark spore masses on host plants, such as grasses and cereal crops. Smuts can be found on many grasses, especially on Johnson grass when it first flowers. Their spore size ranges from 5 to 10 micrometers (microns).

Stachybotrys requires high water activity levels to grow. They are hydrophilic (moisture-loving or high water activity) and are considered a moisture indicator. Stachybotrys is a slow spore produce and it grows on wet cellulose-containing materials (including drywall, paper, ceiling tiles, wallpaper and wicker), which have been moist for an extended period of time. Stachybotrys spores are coated with a mucilaginous layer, and do not become easily airborne. Spores of Stachybotrys detected indoors are excellent indicators of water damage.

Stemphylium is reported to be allergenic and are isolated from dead plants and cellulose materials.  It is commonly considered as a contaminant.

Torula is a ubiquitous outdoor fungal organism found in soil, dead herbaceous stems, wood, grasses, sugar beet root, groundnuts and oats and is commonly associated with Type I allergies (hay fever, asthma).  It can be found indoors on cellulose containing materials such as jute, old sacking, wicker, straw baskets, wood and paper.

Trichoderma is a widespread soil fungus. It is a strong cellulolitic fungus that requires high water activity levels to grow.Trichoderma is considered a moisture indicator. It can grow indoors on a variety of materials, typically on wallpaper, wood, carpet, and unglazed ceramics. The spores are small, round, and contain a characteristic green pigment.

Ulocladium is frequently isolated from air, cellulose materials, decaying or dead plant materials, dust (especially mattress dust), gypsum board, soil, paper, paint, textiles, water from humidifiers and wood. 

The preceding fungal types/genera are for descriptive purposes only and the limited medical information provided does not necessarily pertain to the majority of society who are considered normal, healthy individuals. The presence of the fungal spores in a sample does not indicate that any personal exposure has occurred.