Characterization of the microbial community aerosolized in residential showers

A wide range of microorganisms are present in the tap water that reaches residential homes, including potential pathogens. Additionally, biofilms that contain potential pathogens grow in residential premise plumbing, in showerheads, and on shower-associated surfaces. Showers produce respirable droplets, and thus may aerosolize microbes from the water or from shower-associated biofilms. Inhalation of bioaerosols containing potential pathogens is an important human infection route, and previous studies have implicated showers as a source of airborne microbial infections. However, no previous studies have fully characterized the transient changes in the airborne microbial community resulting from residential shower operation. This study is the first to characterize the short-term changes in the airborne bacterial community resulting from shower operation using molecular methods. Shower aerosol samples were collected with a high-throughput bioaerosol sampler, which allowed the collection of short-duration samples to provide a time-series picture of the transient changes in the airborne microbial community during shower operation. Culture-independent molecular methods were used to quantify the microbial aerosol loads during shower operation, and to identify the genus-level diversity and relative abundances of bacteria present in shower bioaerosols. The results of this research show that residential shower operation does result in an increase in airborne bacterial loads, and impacts the airborne bacterial community diversity. The relative abundances of many specific bacterial genera, some of which contain pathogenic species, were increased during shower operation. Overall, the airborne bacterial community during shower operation is different than the ambient, background airborne community. This research additionally compared different methods to extract DNA from short-duration, environmental bioaerosol samples. The results indicate that different extraction methods can significantly impact resultant microbial quantity and diversity estimates. An extraction method for bioaerosol samples should be chosen carefully based on the specific goals of each research project.