16S rRNA gene surveys to quantify pathogens in environmental bioaerosols

This dissertation reports 16S rRNA gene surveys of bacterial communities in four different environments. First, the inoculum of a microbial fuel cell and an anode biofilm after three months of operation revealed an enrichment of several known electron-transferring bacteria. Second, shower water and aerosols collected from a stem cell transplant unit were studied with aid of gene surveys. Potential pathogens from shower water and aerosols have been suggested as an environmental source of infection for immunocompromised patients. We investigated four shower stalis before and after installing membrane-integrated showerheads and found a 99.6% and 82.4% reduction in bacterial counts within the water and aerosol, respectively. 16S rRNA gene surveys revealed potentially pathogenic organisms in both water and aerosol samples from the conventional shower. Most notable were the presence of Mycobacterium mucogenicum in the water and Pseudomonas aeruginosa in the aerosols. Results indicate membrane-integrated showerheads may protect immunocompromised patients from water-borne infections in the stem cell transplant unit, but epidemiological studies are necessary to investigate if membrane-integrated showerheads reduce hospital-acquired infections. Third, metalworking fluids and metalworking bioaerosols were investigated with gene surveys. Despite biocide use in the metalworking industry, the metalworking fluids sustain significant biological growth that can be aerosolized with high shear forces and excess heat incurred during machining processing. Metalworking fluid and aerosol samples were collected during two seasons near two machines, while HEPA filtration systems were either ON or OFF. These analyses did not show a significant difference in bacterial concentration with HEPA filtration, and 16S rRNA gene surveys determined bacteria of potential epidemiologic significance to be present at all times. Fourth, biofilms of eight extubated endotracheal (ET) tubes were studied to identify their community structures. ET tube biofilms were thought to harbor organisms that can lead to ventilator-associated pneumonia. 16S rRNA gene surveys of these biofilms revealed potentially pathogenic sequences in seven of the eight studied ET tubes, showing clearly that pathogenic organism may be harbored within El tube biofilms. Vie found, however, no correlation between intubation duration and 16S rRNA gene concentration. In addition, ET tube biofilm sequences indicated that initial biofilm colonization was caused by oral flora. Other organisms natural to the respiratory tract, GI tract, or the environment may proliferate in this biofilm over a longer time period.