Quantity and diversity of environmental microbial exposure and development of asthma: a birth cohort study

Abstract

BackgroundEarly-life exposure to environmental microbial agents may be associated with the development of allergies. The aim of the study was to identify better ways to characterize microbial exposure as a predictor of respiratory symptoms and allergies.MethodsA birth cohort of 410 children was followed up until 6 years of age. Bacterial endotoxin, 3-hydroxy fatty acids, N-acetyl-muramic acid, fungal extracellular polysaccharides (EPS) from Penicillium and Aspergillus spp., β-D-glucan, ergosterol, and bacterial or fungal quantitative polymerase chain reactions (qPCRs) were analyzed from dust samples collected at 2 months of age. Asthma, wheezing, cough, and atopic dermatitis were assessed using repeated questionnaires. Specific IgEs were determined at the age of 1 and 6 years.ResultsOnly few associations were found between single microbial markers and the studied outcomes. In contrast, a score for the total quantity of microbial exposure, that is, sum of indicators for fungi (ergosterol), Gram-positive (muramic acid) bacteria, and Gram-negative (endotoxin) bacteria, was significantly (inverted-U shape) associated with asthma incidence (P < 0.001): the highest risk was found at medium levels (adjusted odds ratio (aOR) 2.24, 95% confidence interval (95% CI) 0.87–5.75 for 3rd quintile) and the lowest risk at the highest level (aOR 0.34, 95% CI 0.09–1.36 for 5th quintile). The microbial diversity score, that is, sum of detected qPCRs, was inversely associated with risk of wheezing and was significantly (inverted-U shape) associated with sensitization to inhalant allergens.ConclusionScore for quantity of microbial exposure predicted asthma better than single microbial markers independently of microbial diversity and amount of dust. Better indicators of total quantity and diversity of microbial exposure are needed in studies on the development of asthma.

Microbiological characterization of 3193 French dwellings of Elfe cohort children

“…The 10 targets were simultaneously analyzed and provided essential information about the microbiology of different dwellings. It is for this reason that our study is original with respect to those that target only fungi communities (Reponen et al, 2013;Reponen et al, 2011;Vesper et al, 2007b;Vesper et al, 2007c) or studies which characterized cumulative microorganism exposure (Ege et al, 2011;Karvonen et al, 2014;Roussel et al, 2011).…”

“…In the PARSIFAL study (Ege et al, 2011;Schram-Bijkerk et al, 2005), dust endotoxins, Aspergillus and Penicillium extracellular polysaccharides and β-1,3-glucan levels were higher in control children's dwellings than in wheezers' homes. In the PASTURE study (Karvonen et al, 2014), children exposed to molds, bacteria and/or endotoxins developed fewer allergic diseases than children less exposed.…”

“…The birth cohort Epidemiology of Home Allergens and Asthma Study (EHAAS) analyzed fungal and bacterial biomarkers such as β-d glucans, endotoxins, muramic acid and ergosterol in family room dust samples (Sordillo et al, 2011). Finally, only a few studies have done specific microbial measurement with standardized tools like quantitative Polymerase Chain Reaction (qPCR) (Karvonen et al, 2014;Reponen et al, 2012;Reponen et al, 2011).…”

The Role of Dendritic Cells and Monocytes in the Maintenance and Loss of Respiratory Tolerance

“…Epidemiological studies have established environmental exposures that can increase or decrease a child’s risk of developing asthma and/or atopy. Factors that decrease risk include growing up on farms, consumption of raw milk, and exposure to microbial products early in life (2–6). One recent epidemiological study of over 8000 children found exposure to specific types of farming, including exposure to hay, pigs, and poultry, provided protection from asthma (7).…”

Early age exposure to moisture damage and systemic inflammation at the age of 6 years

“…30 Taken together, our current and previous findings can be seen as surrogates from a rich microbial exposure, which is inversely associated with the development of asthma. 31 A key strength of this study was the objectively inspectorbased report of moisture damage and mold within the homes using standardized methods. Moreover, this is the first prospective study looking at early age exposure to moisture damage and mold in relation to inflammatory markers among children assessed in later childhood.…”