The research is based on a study of three North American cities. The research is based out the main contributor to microorganisms in the built environment coming from organisms carried by rafts of human skin, which people shed on a regular basis. A secondary source is transfer via shoes, often taking organisms from the outside environment inside a building.
The study was relatively small in that a selection of offices were monitored in each of the cities. However, a degree of experimental robustness was added through the study running for one year, with samples taken at regular intervals. The cities were: Flagstaff, San Diego and Toronto.
Within the offices, different types of surfaces were sampled. These included a painted wall, a ceiling tile, and carpet. Samples were also taken from the people who worked in the offices. As well as collecting microorganisms other data relating to the indoor environment was measured, including temperature and humidity. A note was also taken of occupancy.
The microorganisms collected were characterized using advanced molecular biology methods, examining a highly conserved region of the bacterial genome called the 16S rRNA segment. This region is not prone to changing due to environmental factors. For fungi, a different approach was used at the genetic level.
The key findings were:
Floor samples contain the highest numbers of microorganisms;
The numbers of microorganisms did not significantly alter over time;
Many microorganisms derived from human skin, especially from the nasal area;
Temperature and humidity were not significant factors in shaping the microbial profile;
The majority of the microorganisms came from the outside environment;
Each city had a different microbial profile (which the researchers are calling a “signature.”)
Thus the overall finding was that geography is a key determinant of the types of microorganisms recovered from the indoor environment. This is due to the majority of isolates, found inside, come from the outside.
The research suggests that, in the absence of disasters like flooding, a general microbial profile can be built up for each city environment.
The findings are not only of academic interest, for observing changes in the microbial profile can help inform about factors that might impact upon human health.
The research, carried out at the Northern Arizona University in Flagstaff, is published in the journal mSystems and the research paper is titled “Geography and Location Are the Primary Drivers of Office Microbiome Composition.”
