Abstract
The indoor microbial community is a mixture of microorganisms resulting from outdoor ecosystems that seed the built environment. However, the biogeography of the indoor microbial community is still inadequately studied. Dust from more than 3000 dwellings across France was analyzed by qPCR using 17 targets: 10 molds, 3 bacteria groups, and 4 mites. Thus, the first spatial description of the main indoor microbial allergens on the French territory, in relation with biogeographical factors influencing the distribution of microorganisms, was realized in this study. Ten microorganisms out of 17 exhibited increasing abundance profiles across the country: Five microorganisms (Dermatophagoïdes pteronyssinus, Dermatophagoïdes spp., Streptomyces spp., Cladosporium sphaerospermum, Epicoccum nigrum) from northeast to southwest, two (Cryptococcus spp., Alternaria alternata) from northwest to southeast, Mycobacteria from east to west, Aspergillus fumigatus from south to north, and Penicillium chrysogenum from south to northeast. These geographical patterns were partly linked to climate and land cover. Multivariate analysis showed that composition of communities seemed to depend on landscapes, with species related to closed and rather cold and humid landscapes (forests, located in the northeast) and others to more open, hot, and dry landscapes (herbaceous and coastal regions, located in the west). This study highlights the importance of geographical location and outdoor factors that shape communities. In order to study the effect of microorganisms on human health (allergic diseases in particular), it is important to identify biogeographic factors that structure microbial communities on large spatial scales and to quantify the exposure with quantitative tools, such as the multi-qPCR approach.
Highlights
Individual allergic sensitivity is the main risk factor for asthma development and the early childhood environment is important in the development of allergic diseases [1]
The present study addressed the biogeography of indoor microbial exposure, providing an assessment of the microbial composition of French dwellings in terms of molds, bacteria, and dust mites using a single standardized quantification method
Given the importance of seasonality on the distribution of microorganisms, the purpose of this paper was to be able to assess the respective weight of geographical location by taking into account the month effect by means of statistical processing (GAMMs and partial redundancy analysis (pRDA)) and to evaluate the influence of, probably, the two most important parameters
Summary
Individual allergic sensitivity is the main risk factor for asthma development and the early childhood environment is important in the development of allergic diseases [1] Both protective [2] and harmful effects [3,4,5] of environmental indoor microorganisms have been suggested, but the exact role of bacteria, molds and mites remains unknown, and there is no at-risk or protective threshold available for any species [6]. It is expected that the geographical location of a dwelling (and the associated climatic parameters and type of land use) may influence its microbial contamination [14,15,16,17] It has been shown, for example, that the geographical position of an outdoor dust sample can be identified, within a median error of 230 km, based on the fungal biome identified [18]. Geographical location as a factor influencing indoor microbial communities remains largely unstudied, with only three studies that evaluated fungal and/or bacterial contamination across the USA [19,20,21]
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