Chaetomium globosum is a hydrophilic mold with a worldwide distribution that is commonly found in water damaged buildings. C. globosum produces several well described mycotoxins. It is a sporadic cause of infectious mycosis in humans. It is also thought to be an important allergen in the pathogenesis of allergic respiratory disease associated with living and working in damp buildings. There are no recognized C. globosum specific allergens and the degree of cross-reactivity with other fungal and non-fungal allergens is yet to be determined. 

Worldwide distribution 

C. globosum is found worldwide, most commonly colonizing soil, straw, seeds, cereals, cardboard, paper, cotton, foam and fabric. The percentage of patient sera positive to a group of molds associated with building damp is broadly proportional to their occurrence in buildings, in contrast to fungal species for which exposure is universal, such as Aspergillus fumigatus and A. alternata (2).

A study from West Virginia, where one of the highest hospitalization rates for asthma in pediatric patients in the US is reported, measured the prevalence of hypersensitivity to C. globosum amongst patients with atopy (n=102). They found that 21% of patients reacted to one or more fungal allergens and that 7% of patients were sensitive to C. globosum (7). C. globosum was among a series of novel fungal challenges that the researchers used in parallel with a routine allergy-testing panel. The study demonstrated that 19% of fungal hypersensitivities would have been missed if the standard panel had been used alone. Similarly, a study from Poland has found 7% of a cohort of atopic patients were sensitized to C. globosum (8).

Living environment

C. globosum has been isolated from soil, animal dung, food, paper, textiles, plywood, carpet, wallpaper and wet walls (1). However, it is thought to be its capacity to colonize cellulose-based building material, such a gypsum boards, that is key to its ubiquity in water-damaged and damp homes (5). The profile of indoor fungal species varies across the United States. However, specific fungal genera appear to be ubiquitous, including Chaetomium (7). 

Main

Although direct evidence of aerosolized fungal fragments and respiratory disease is yet to be demonstrated, it is proposed that C. globosum is the cause of allergic disease through inhalation of specific allergen (7).

There is consensus in the literature from epidemiological studies conducted in Europe, Canada and the USA that exposure to mold allergens has a significant health impact on people living and working in damp buildings. With an increased risk for respiratory symptoms, including asthma, hypersensitivity pneumonitis, and rhinosinusitis. Furthermore, indoor dampness and mold increase the risk of hypersensitivity to other allergens, such as house dust mites and pollen (5). It is estimated that between 10 and 30% of homes in North America have damp-associated mold problems, resulting in significant health and economic burden (2). However, no reported occupational risk is associated with this C. globosum (9).

Allergenic molecules

Currently, no allergens are recognized by the WHO/IUIS Allergen Nomenclature Sub-committee. However, identifying allergens from fungi that grow on building materials is a priority for the US National Academy of Sciences panel on asthma, indicating the scale of the public health risk posed (2).

Mycotoxins associated with food and agriculture are well described; however, there is relatively little in the literature about mycotoxins in damp buildings. Several mycotoxins produced by C. globosum have been the focus of interest as potential allergens. C. globulosum strains from Canada produce chaetoglobosins A, C and F, chaetomugilin D; and chaetoviridin A with other chaetoglobosins and azaphilones in smaller amounts. Chaetoglobosin A and Chaetomugulin D have been studied in the mouse alveolar macrophage cell line, where an inflammatory effect has been demonstrated with upregulation of chemokine TNF-α (5). Furthermore, C. globosum inoculation on gypsum board results in chaetoglobosins A and C production as high as 50 µg/cm² (10).

C. globosum produces a range of intracellular and extracellular antigens. C. globosum enolase is a 45–50 kDa enzyme with a role in fungal glycolysis. It is an immunodominant antigen secreted during hyphal growth by various fungal species, including Saccharomyces cerevisiae, Candida albicans, Cladosporium herbarum, Curvularia lunata, Alternaria alternata, Penicillium citrinum, Rhodotourla mucilaginosa, Aspergillus versicolor and Aspergillus fumigatus (10).

Furthermore, high molecular weight C. globosum chitinases (45 kDa and 47 kDa [Chg47]), identified by ELISA and immunoblotting tests, have been shown to be allergenic (2). A Chg47 monoclonal antibody assay can be used to identify C. globosum in house dust spores and is a potential tool for allergen exposure assessment (8). 

Cross-reactivity

In the study on patients with atopy from West Virginia, researchers noted multiple IgE reactive bands on immunoblotting that were not inhibited by other common aeroallergens. The authors concluded that further work was required to determine cross-reactivity between the fungal species studied (7). 

Author: RubyDuke Communications

Reviewer: Dr. Christian  Fischer

Last reviewed: January  2022