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Early-life exposure to microbial agents may play a protective role in asthma and allergies development. Geographical differences in the prevalence of these diseases exist, but the differences in early-life indoor microbial agent levels and their determinants have been hardly studied. We aimed to describe the early-life levels of endotoxin, extracellular polysaccharides ( EPS), and β(1-3)-glucans in living room dust of four geographically spread European birth cohorts (LISA in Germany, PIAMA in the Netherlands, INMA in Spain, and LUKAS2 in Finland) and to assess their determinants. A total of 1572 dust samples from living rooms of participants were analyzed for endotoxin, Penicillium/Aspergillus EPS, and β(1-3)-glucans. Information on potential determinants was obtained through questionnaires. Concentrations of endotoxin, EPS, and β(1-3)-glucans were different across cohorts. Concentrations of endotoxin and EPS were respectively lower and higher in INMA than in other cohorts, while glucans were higher in LUKAS2. Season of sampling, dog ownership, dampness, and the number of people living at home were significantly associated with concentrations of at least one microbial agent, with heterogeneity of effect estimates of the determinants across cohorts. In conclusion, both early-life microbial exposure levels and exposure determinants differ across cohorts derived from diverse European countries. [ABSTRACT FROM AUTHOR]

Background: In order to enable reproducible and comparable exposure measurements of fungal alpha-amylase (alpha-amylase) in different laboratories and countries, the entire procedure from sampling of airborne dust to measuring extracted samples (including standards and the used enzyme) immunoassays must be standardized. The aim of this study was to establish optimal elution and assay conditions., Methods: A parallel sampler was used for simultaneous collection of 10 samples of inhalable dust in bakeries and mills in Germany, England, the Netherlands and Spain. Three enzyme-immunoassays (EIAs) for detection of fungal alpha-amylase based on monoclonal antibodies or polyclonal antibodies were used for the measurement of the parallel-sampled filters (n=432) extracted using several methods. The results were analysed by regression analysis of variance. Additional filters (n=54) were extracted and analysed using two EIAs to investigate the storage stability of the extracts., Results: Although alpha-amylase concentrations correlated well (r> or =0.88), differences were found between the EIAs in the sensitivity and nominal values (up to a mean factor 5.8). The best elution medium for airborne filters (phosphate-buffered saline 'PBS' with 0.05% Tween-20) led to 1.2 to two times higher alpha-amylase allergen yields than extraction in PBS only, while higher Tween-20 concentrations decreased the extracted alpha-amylase yield. During storage of frozen dust/filter extracts for 3-4 months at -20 degrees C, a loss of approximately 40% of measurable alpha-amylase was observed, which could be partially prevented by addition of 0.1% casein to the medium directly after extraction., Conclusion: Although the effects of only a few of many possible causes of variation were investigated, for these factors a clear choice could be made with regard to optimal elution conditions and the use of validated EIAs with calibrated standards, thus making significant progress towards a completely standardized procedure for airborne alpha-amylase measurements.