Indoor airborne bacterial communities are influenced by ventilation, occupancy, and outdoor air source

Abstract

Architects and engineers are beginning to consider a new dimension of indoor air: the structure and composition of airborne microbial communities. A first step in this emerging field is to understand the forces that shape the diversity of bioaerosols across space and time within the built environment. In an effort to elucidate the relative influences of three likely drivers of indoor bioaerosol diversity – variation in outdoor bioaerosols, ventilation strategy, and occupancy load – we conducted an intensive temporal study of indoor airborne bacterial communities in a high-traffic university building with a hybrid HVAC (mechanically and naturally ventilated) system. Indoor air communities closely tracked outdoor air communities, but human-associated bacterial genera were more than twice as abundant in indoor air compared with outdoor air. Ventilation had a demonstrated effect on indoor airborne bacterial community composition; changes in outdoor air communities were detected inside following a time lag associated with differing ventilation strategies relevant to modern building design. Our results indicate that both occupancy patterns and ventilation strategies are important for understanding airborne microbial community dynamics in the built environment.

Characterization of culturable airborne bacteria and antibiotic susceptibility profiles of indoor and immediate-outdoor environments of a research institute

“…This data supports a study conducted on understanding airborne microbial dynamics in built environments, which indicated that indoor airborne bacterial communities are influenced by outdoor air source and ventilation 26 . Classrooms and laboratories sampled were air-conditioned; therefore bacterial contamination of air reported in this study is inevitable, especially when the air conditioner blades are not properly or frequently cleaned.…”

The bacterial composition of ventilation filter dust in Norwegian pre-school nurseries

“…The genera indicated were Micrococcus, Streptococcus, Corynebacterium, Propionibacterium, and Staphylococcus. 14,17,[30][31][32] Sequences classified as Micrococcus and Streptococcus were dominant in exhaust samples making up 16% and 8% of the sequences respectively. Some genera which include primary pathogenic species, such as Legionella sp., Burkholderia sp., Neisseria sp., and Mycobacterium sp.…”

Humans differ in their personal microbial cloud.

“…These are hereafter referred to as "targeted OTUs." Specifically, we selected these families based on three criteria: (1) OTUs representing these families were consistently significant predictors of human occupants vs background air in the first experiment (Table 3); (2) the relative abundances of these families were always elevated in occupied samples compared to unoccupied samples; and (3) all of these families are consistently detected as members of the healthy human microbiome (HMP Consortium, 2012;Grice & Segre, 2011;Ravel et al, 2011), and as indicators for human occupancy in the built environment (Fierer et al, 2010;Flores et al, 2011;Meadow et al, 2013;Kembel et al, 2014;Meadow et al, 2014).…”

“…Humans harbor diverse microbial assemblages in and on our bodies (HMP Consortium, 2012), and these distinctly human-associated bacteria can be readily detected inside of buildings on surfaces, in dust, and as bioaerosols Täubel et al, 2009;Fierer et al, 2010;Flores et al, 2011;Flores et al, 2013;Meadow et al, 2013;Kembel et al, 2012;Kembel et al, 2014). Human-associated bacteria disperse into and throughout the built environment by three primary mechanisms: (1) direct human contact with indoor surfaces; (2) bioaerosol particle emission from our breath, clothes, skin and hair; and (3) resuspension of indoor dust containing previously shed human skin cells, hair and other bacteria-laden particles.…”

“…Research on bioaerosols to date has rarely focused on the direct emission of bioaerosols from human sources, because it is difficult to disentangle direct emission from resuspension of dust observationally (Meadow et al, 2013;Qian et al, 2012;Qian, Peccia & Ferro, 2014;Nazaroff, 2014;Hospodsky et al, 2014;Bhangar et al, 2015;Adams et al, 2015). Previous attempts to account for dust resuspension in indoor bioaerosols indicate that active human emission, as opposed to resuspended particulate matter, is an underestimated part of the total indoor airborne bacterial pool in buildings (Qian, Peccia & Ferro, 2014).…”