There are over 100,000 species of fungi. Many fungi are good and useful (edible mushrooms would be an example of these) while some cause problems (some fungi can injure plants and humans).  Every week the IEQ Review will describe a specific microorganism, its morphological origin and potential health effects.  If you would like to know about a specific organism and/or would like it published in The IEQ Review please email Dr. Rajiv Sahay with the Environmental Diagnostics Laboratory (EDL) at Pure Air Control Services laboratory@pureaircontrols.com.

This week we will cover ...   

Chaetomium sp.


 
Chaetomium is a dematiaceous filamentous fungus found in soil, air, and plant debris. As well as being a contaminant, Chaetomium spp. are also encountered as causative agents of infections in humans. Some species are thermophilic and neurotropic in nature.
 
 Chaetomium spp. are among the fungi causing infections wholly referred to as phaeohyphomycosis. Fatal deep mycoses due to Chaetomium atrobrunneum have been reported in an immunocompromised host. Brain abscess, peritonitis, cutaneous lesions, and onychomycosis may also develop due to Chaetomium spp.

Septate hyphae, perithecia, asci and ascospores are visualized. Perithecia are large, dark brown to black in color, fragile, globose to flask shaped and have filamentous, hair-like, brown to black appendages (setae) on their surface. Perithecia have ostioles (small rounded openings) and contain asci and ascospores inside. Asci are clavate to cylindrical in shape and rapidly dissolve to release their ascospores (4 to 8 in number). Ascospores are one-celled, olive brown in color, and lemon shaped.

Chaetomium colonies are rapidly growing, cottony and white in color initially. Mature colonies become grey to olive in color. From the reverse, the color is tan to red or brown to black.