Molds excrete extracellular enzymes and proteins to digest and absorb nutrients from substrates that include lipases, proteinases, chitinases, amylases, esterases, phospho-lipases, siderophores and haemolysins, among others (Birch et al, 2004; Donohue et al, 2005, 2006; Hu et al, 2004; Kudanga et al, 2007; Mellon et al, 2007; Moon, et al, 2006; Schretti et al, 2007; Vesper and Vesper, 2004; Vesper et al, 2004; Yike et al, 2007).
Inhaled microbial proteinases cause inflammation in the respiratory tract, activating protease receptors with production of IL-6, IL-8 and release of IL6, IL-8, PGE2, granulocyte-macrophage colony-stimulating factor (GMCSF). Neutrophils and eosinophils are recruited (Asokananthan et al, 2002; Chiu et al, 2007; Reed, 2007; Shin et al, 2006; Yike et al, 2005, 2007). In addition, siderophores that bind iron have a distinct role in A. fumigatus infections (Schretti et al, 2007).
An outbreak of infantile pulmonary haemosiderosis in Cleveland was associated with S. chartarum. A haemolysin (stachylysin) and a siderophore were identified from strains of Stachybotrys isolated from the infants’ homes and from a lung of a child with pulmonary haemorrhage (Dearborn et al, 2002; Elidemer et al, 1999; Vesper et al, 2000). The Cleveland cases were criticized by the CDC for statistical errors and limitations in sampling procedures during the initial evaluation of the affected homes (CDC, 2000). However, recent observations indicate that species of mold other than S. chartarum secrete haemolysins.
Several of the mold genera were isolated from the dust of the Cleveland case homes. They were identified to species by quantitative polymerase chain reaction. The isolates were tested for the production of haemolysins (Vesper and Vesper, 2004).
Eleven species of Aspergillus, ten species of Penicillium, two species of Ulocladium, Paecilomyces variotil, Memnoniella echinata, Scopulariopsis brevicaulis, Trichoderma longibrachiatum and viride and S. chartarum were demonstrated to cause haemolysis of sheep’s blood agar. Haemolysins were more often produced by the fungi from homes with pulmonary haemorrhage (42%) than from reference homes (10%).
These observations emphasize the complexity of damp indoor spaces and broaden the possible biological agents responsible for the adverse health effects to occupants of water-damaged indoor environments.
Molds excrete extracellular enzymes
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