We spend much of our lives indoors where we interact with building microbiomes. We have developed methodologies to identify the microbes to which target groups are routinely exposed.
The indoor environment impacts our health and well-being.
By some estimates, we spend 90 percent of our time indoors where we are subjected to a range of exposures - including building microbiomes originating in building users, the surrounding environment and building materials.
According to the EPA, these exposures can have variously neutral, adverse, or beneficial effects depending on the person, their health and microorganism types.
Some microbes are linked to allergies or may be antibiotic resistant or toxin-producing. Conversely, exposure to some other microorganisms early in life may have protective effects.
In the current project we developed methodologies to sample and identify building microbiomes with focus on nursery schools and nursing homes.
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More about the project
People spend much of their day indoors. Here they are exposed to the microorganisms and their products that are present in buildings, often referred to as the indoor microbiome. This contact is now known to have relevance for human health and development.
Ventilation design and rates in homes, and in public buildings such as nursery schools and healthcare facilities, must address a delicate balance between reducing pathogen loads and meeting current energy efficiency standards.
This balance received much attention after the current project period, where increased ventilation rates to reduce the risk of exposure to Covid-containing aerosols, required innovative thinking with regards to energy conservation.
With the advent of high throughput sequencing technologies, exact characterizations of microbial exposures can be attempted.
Through a series of three interrelated studies, we collected both floor dust and dust filter samples from heating, ventilation and air conditioning (HVAC) systems, and characterized the microbial composition of air entering and leaving buildings.
We developed methodologies for isolation of microbes, and microbial DNA and endotoxins from HVAC-filter dust (and nursery floors). Microbial DNA was identified using two NGS approaches, namely Oxford Nanopore MinION and Ilumina MiSeq.
Major findings
A general observation was that ventilation exhaust-filter dust and indoor floor samples had high proportions of human-associated bacterial taxa, some of clinical significance.
In addition, the results of endotoxin and antibiotic resistance gene-analyses showed the presence of both toxins (although at very low concentrations) and resistance genes of clinical relevance.
Culturing of filter samples showed there were far greater numbers of microbes leaving than entering building, and slightly high endotoxin concentrations.
The studies thus provided, albeit indirectly, a description of indoor microbial exposures and how indoor air differed from the surrounding environment.
Furthermore, HVAC performance is often compromised by faults in the system or maintenance. Thus, as part of the study we routinely checked how filters were installed and performing. On one occasion it was found that bag filters were installed with the wrong orientation, so that during pauses in ventilation (weekends), deflated filters trailed the floor where they picked up dust and moisture.
Culturing of indoor surfaces revealed areas of poor hygiene where there was a need for improved cleaning practices.
Early exposures to microbes are known to be important for the development of bodily microbiomes and immune function, and the study was pertinent in that it showed which organisms kindergarten children are exposed to.
Furthermore, the project showed that indoor microbial communities were clearly structured by human occupancy and that these changed over an 11 month-period from the first weeks of opening of a newly constructed kindergarten.
After isolation of DNA, concentration and identification are required to generate libraries of microbial taxa.
In a bench-mark study which won second prize as a faculty original publication, we found that Oxford Nanopore Minion technology achieved a good, and greater than Illumina MiSeq, taxonomic resolution of indoor microbial communities, particularly at the species level.
This suggested a potential use of the former for future studies of indoor microbial communities.
