Fungal extracellular polysaccharides, beta (1 -> 3)-glucans and culturablefungi in repeated sampling of house dust

Fungal exposure inside homes has been associated with adverse respiratory s ymptoms in children and adults. While fungal assessment has traditionally r elied upon questionnaires, fungal growth on culture plates and spore counts , new immunoassays for extracellular polysaccharides (EPS) and beta (1-->3) -glucans have enabled quantitation of fungal agents in house dust in a more timely and cost-effective manner, possibly providing a better measure of f ungal exposure. We investigated associations among measurements of EPS, bet a (1-->3)-glucans and culturable fungi obtained from 23 Dutch homes. From e ach home, dust samples were vacuumed from the living room floor twice durin g 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, beta ( 1-->3)-glucans and culturable fungi. EPS was positively associated with glu can; an increase from the 25th to the 75th percentile of glucan concentrati on 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 gl ucan concentrations were the surface type that was vacuumed an the concentr ation of total culturable fungi (in colony forming units (CFU)/g dust), wit h 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 <mu>g/g). These positive associations suggest that house dust co ncentrations of beta (1-->3)-glucan, and particularly those of EPS, are goo d markers for the overall levels of fungal concentrations in floor dust whi ch is a surrogate for estimating airborne fungal exposure.