Main content area

Potentially Pathogenic Bacteria in Shower Water and Air of a Stem Cell Transplant Unit

Perkins, Sarah D., Mayfield, Jennie, Fraser, Victoria, Angenent, Largus T.
Applied and environmental microbiology 2009 v.75 no.16 pp. 5363-5372
Mycobacterium mucogenicum, Pseudomonas aeruginosa, aerosols, air, bacteria, cell transplantation, cross infection, disease control, epidemiological studies, hospitals, indoor environmental quality, microbial contamination, microbial load, nucleotide sequences, pathogens, plate count, polymerase chain reaction, public water supply, quantitative analysis, ribosomal RNA, risk reduction, stem cells, surveys, tap water, water pollution, waterborne diseases
Potential pathogens from shower water and aerosolized shower mist (i.e., shower aerosol) have been suggested as an environmental source of infection for immunocompromised patients. To quantify the microbial load in shower water and aerosol samples, we used culture, microscopic, and quantitative PCR methods to investigate four shower stalls in a stem cell transplant unit at Barnes-Jewish Hospital in St. Louis, MO. We also tested membrane-integrated showerheads as a possible mitigation strategy. In addition to quantification, a 16S rRNA gene sequencing survey was used to characterize the abundant bacterial populations within shower water and aerosols. The average total bacterial counts were 2.2 x 10⁷ cells/liter in shower water and 3.4 x 10⁴ cells/m³ in shower aerosol, and these counts were reduced to 6.3 x 10⁴ cells/liter (99.6% efficiency) and 8.9 x 10³ cells/m³ (82.4% efficiency), respectively, after membrane-integrated showerheads were installed. Potentially pathogenic organisms were found in both water and aerosol samples from the conventional showers. Most notable was the presence of Mycobacterium mucogenicum (99.5% identity) in the water and Pseudomonas aeruginosa (99.3% identity) in the aerosol samples. Membrane-integrated showerheads may protect immunocompromised patients from waterborne infections in a stem cell transplant unit because of efficient capture of vast numbers of potentially pathogenic bacteria from hospital water. However, an in-depth epidemiological study is necessary to investigate whether membrane-integrated showerheads reduce hospital-acquired infections. The microbial load in shower aerosols with conventional showerheads was elevated compared to the load in HEPA-filtered background air in the stem cell unit, but it was considerably lower than typical indoor air. Thus, in shower environments without HEPA filtration, the increase in microbial load due to shower water aerosolization would not have been distinguishable from anticipated variations in background levels.