Fungal extracellular polysaccharides, (13)-glucans and culturable fungi in repeated sampling of house dust
Chew, G. L., Douwes, J., Doekes, G., Higgins, K. M., Strien, R. V., Spithoven, J. and Brunekreef, B.
2001 Indoor Air, 11(3): 171
Chew, G. L., Douwes, J., Doekes, G., Higgins, K. M., Strien, R. V., Spithoven, J. and Brunekreef, B., (2001), "Fungal extracellular polysaccharides, (13)-glucans and culturable fungi in repeated sampling of house dust", Indoor Air, 11(3): 171.
Abstract:
Fungal exposure inside homes has been associated with adverse respiratory symptoms in children and adults. While fungal assessment has traditionally relied upon questionnaires, fungal growth on culture plates and spore counts, new immunoassays for extracellular polysaccharides (EPS) and (13)-glucans have enabled quantitation of fungal agents in house dust in a more timely and cost-effective manner, possibly providing a better measure of fungal exposure. We investigated associations among measurements of EPS, (13)-glucans and culturable fungi obtained from 23 Dutch homes. From each home, dust samples were vacuumed from the living room floor twice during the Fall, Winter and Spring seasons for a total of six collections (every 6 weeks from October 1997 to May 1998). Samples were sieved and fine dust was analyzed for EPS from Aspergillus and Penicillium spp. combined, (13)-glucans and culturable fungi. EPS was positively associated with glucan; an increase from the 25th to the 75th percentile of glucan concentration was associated with a 1.6-fold increase in EPS concentration (95% CI=1.3 to 2.0; p<0.01). The most significant variables associated with EPS and glucan concentrations were the surface type that was vacuumed and the concentration of total culturable fungi (in colony forming units (CFU)/g dust), with an increase in CFU/g from the 25th to the 75th percentile associated with a 1.3 (1.1-1.6)-fold increase in glucan and a 1.7 (1.3-2.2)-fold increase in EPS concentrations. In addition, the within-home variation of EPS levels were smaller than those between homes (25,646 U/g vs. 50,635 U/g), whereas the variation of glucan levels was similar within and between homes (1,300 vs. 1,205 g/g). These positive associations suggest that house dust concentrations of (13)-glucan, and particularly those of EPS, are good markers for the overall levels of fungal concentrations in floor dust which is a surrogate for estimating airborne fungal exposure.
Practical Implications
Traditional microscopic methods of fungal exposure assessment in the home environment are difficult because of the expense in terms of time and money. This study provides a comparison of a traditional method (culture plate sampling followed by microscopy) and relatively new immunoassays that measure fungal extracellular polysaccharides (EPS from Aspergillus and Penicillium spp. combined) and (13)-glucans. The concentration of total culturable fungi was positively associated with EPS and glucan. Our results suggest that house dust concentrations of (13)-glucan, and particularly those of EPS, are good markers for the overall levels of fungal concentrations in floor dust which is a surrogate for estimating airborne fungal exposure
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