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Chaetomium Mold Species
The U.S. Government's Occupational Safety and Health Administration [OSHA] classifies Chaetomium species as an allergen and irritant and a cause of Hypersensitivity Pneumonitis and Dermatitis.
Chaetomium species are causative agents of cutaneous lesions and Onychomycosis. (Information from www.doctorfungus.org @ 2005)
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Taxonomic Classifications
Kingdom:
Fungi
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Ecology
Chaetomium is a dematiaceous filamentous fungus isolated from soil, air, and from decomposing plant debris, especially woody or straw – like materials and from herbivore dung. Aside from being a contaminant, Chaetomium species are also encountered as causative agents of infections in humans. Additionally, some species are thermophilic and neurotropic in nature.
Species
The genus Chaetomium contains a number of species. The most widespread ones are Chaetomium atrobrunneum, Chaetomium funicola, Chaetomium globosum, and Chaetomium strumarium.
Pathogenicity and Health Effects
Chaetomium species are among the fungi causing infections referred to as phaeohyphomycosis. Cases of fatal deep mycoses in an immunocompromised patient due to Chaetomium atrobrunneum have been reported. Brain abscess, peritonitis, cutaneous lesions, and onychomycosis may also develop due to Chaetomium species.
Macroscopic Appearance
Ø Growth rate is rapid and colony texture is cottony; and Ø Surface colony color is white initially but as colonies mature, color becomes gray to olive while tan to red or brown to black on the reverse.
Microscopic Appearance
Ø The hyphae are septate, hyaline to pale brown; Ø Perithecia, asci and ascospores are present; Ø Perithecia are brown to black in color, large, fragile, globose to flask – shaped and surrounded by long, undulant, helical or erect, spine – like filamentous setae (hair – like appendages); Ø Perithecia have small rounded openings called ostioles which contain asci and ascospores inside; Ø Asci are clavate to cylindrical in shape and remain intact only for a short period of time after their formation (evanescent) and dissolve rapidly to release their ascospores which are usually four to eight in number; Ø Ascospores are unicellular, brown in color, and usually lemon – shaped.
Laboratory Precautions
Only general laboratory precautions are required, no special safety measures needed.
Susceptibility
There is no standard method for in vitro susceptibility testing of Chaetomium species as yet and very few data are available. When a small number of Chaetomium atrobrunneum, Chaetomium funicola, and Chaetomium globosum isolates were tested, it appears that MICs of amphotericin B, ketoconazole, itraconazole, and miconazole were acceptably low while those of fluconazole and flucytosine appeared very high. |
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The mycological information gathered and organized in this extensive research on different Pathogenic Molds was sourced out from the list of informative websites and reference book below:
http://www.osha.gov
A Clinical Laboratory Handbook: Identifying Filamentous Fungi by St. Germain, Guy and R. Summerbell. |
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