Presence of Chaetomium in an Indoor Environment: What Are The Implications?

Chaetomium is one of the most common moulds in water-damaged buildings.

Species of Chaetomium are strongly cellulolytic moulds commonly found in soil, on paper, straw, cloth, cotton and other cellulose-containing substrates. They have caused problems in libraries, archives, and the food industry. Because of their bio-deterioration ability, several strains are used in testing materials for mould growth resistance.

Concentrations of Chaetomium spores in the air: why are they usually low?

Spores (ascospores) of Chaetomium are produced within structures (asci) contained in a flask-shaped fruiting body known as perithecium. On spore maturity, the walls of the asci dissolve releasing mucilaginous spores within the perithecium. The spores ooze out of the perithecium (plural perithecia) and get trapped by coiled or dichotomously branched hairs that grow around the neck of the perithecium.

Since the spores are cemented together by mucilage and also trapped by hairs, few become airborne until the mould has completely dried out or disturbed, say during renovations or mould remediation. It is therefore not uncommon to find low Chaetomium spore counts in pre-remediation mould test samples and relatively higher counts in post-remediation samples.

Chaetomium as a health hazard, indoor air biocontaminant and biodeteriorator

Some species of Chaetomium have been implicated in nosocomial infection of patients in hospital environment after bone marrow transplantation (9). Many species are also known to produce mycotoxins (6, 8) and are recognized human allergens (2). The most common species in water-damaged buildings is Chaetomium globosum. In many cases it occurs together with Stachybotrys chartarum and other hydrophilic moulds. It produces high quantities of biomass (up to 10 mg/cm²) on building materials (3).

It has been isolated from wallpaper, drywall, baseboards, carpets and window frames. It is a major cause of biodeterioration of paper and other cellulose containing materials. As a health hazard, Chaetomium globosum produces very high quantities of mycotoxins, especially chaetoglobosins A and C when growing on gypsum board (4, 6). It is a known agent of skin and nail infections in humans and is more rarely a cause of cerebral and systemic infections in immunocompromised individuals (1, 7).

Although Chaetomium globosum is reported to have type I & III allergens (5) the spores are not easily aerosolized and hence exposure to airborne spores may be rather limited. However, exposure to cytotoxic mycotoxins and also fine hyphal fragments released from dried mycelia could be a major concern.

References

1. Abbott, S. P., L. Sigler, R. McAleer, D. A. McGough, M. G. Rinaldi, and G. Mizell.1995. Fatal cerebral mycoses caused by the ascomycete Chaetomium strumarium. J. Clin. Microbiol. 33:2692-2698.
2. Liebeskind, A. 1972. Mycological problems in occupational allergies. J. Asthma Res. 10:71–73.
3. Nielsen, K.F, (2002), “Mould growth on building materials: Secondary metabolites, mycotoxins and biomarkers”, Dissertation, The Mycology Group, Technical University of Denmark.
4. Nielsen, KF, Gravesen S, Nielsen PA, Andersen B, Thrane, Frisvad JC. 1999. Production of mycotoxins on artificially and naturally infested building materials. Mycopathologia 145:43-56.
5. Pieckova, E. (2003). In vitro toxicity of indoor Chaetomium Kunze ex Fr. Ann. Agric. Environ. Med. 10(1):9-14.
6. Sekita, S., K. Yoshihira, S. Natori, S. Udagawa, T. Muroi, Y. Sugiyama, H. Kurata, and M. Umeda. 1981. Mycotoxin production by Chaetomium spp. and related fungi. Can. J. Microbiol. 27:766–772.
7. Serena, C. et al. (2003). In vitro activities of new antifungal agents against Chaetomium spp. and inoculum standardization. Antimicrob. Agents Chemother. 47(10):3161-3164.
8. Udagawa, S., T. Muroi, H. Kurata, S. Sekita, K. Yoshihira, and S. Natori. 1979. The production of chaetoglobosins, sterigmatocystin, O-methylsterigmatocystin, and chaetocin by Chaetomium spp. and related fungi. Can. J. Microbiol. 25:170–177.
9. Woods GL, Davis JC, Vasughan WP: Failure of the sterile airflow component of a protected environment detected by demonstration of Chaetomium species colonization of four consecutive immunosupressed occupants. Infect Control Hosp Epidemiol 1988, 9, 451-456.

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Dr Jackson Kung'u

Dr. Jackson Kung’u is a Microbiologist who has specialized in the field of mycology (the study of moulds and yeasts). He is a member of the Mycological Society of America. He graduated from the University of Kent at Canterbury, UK, with a Masters degree in Fungal Technology and a PhD in Microbiology. He has published several research papers in international scientific journals. Jackson has analyzed thousands of mould samples from across Canada. He also regularly teaches a course on how to recognize mould, perform effective sampling and interpret laboratory results. Jackson provides how-to advice on mould and bacteria issues. Get more information about indoor mould and bacteria at www.drjacksonkungu.com.

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