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Bacteria thrive in shower heads and in household water distribution systems. Although most of these bacteria are harmless, some are potentially pathogenic, including members of the genus. mycobacterium may cause lung infections with non-tuberculous mycobacteria (NTM). In a new study published in the journal mbioResearchers at Boulder, a research team led by the University of Colorado, have found that showerheads often host abundant communities of mycobacteria whose composition varies according to geographic location, chemical composition of the water and the water source. They also identified geographic areas in the United States where showerheads have a particularly high abundance of potentially pathogenic mycobacterial lineages, and these "hot spots" typically overlap areas where lung disease due to NCDs is most prevalent.
Mycobacteria are frequently abundant in showerheads and many showerheads harbor mycobacterial lineages including known pathogens.
"Bacteria grow and persist in the biofilms that cover the inside of showerheads and shower hoses, despite the seemingly inhospitable conditions found in these habitats," said Dr. Matthew Gebert, lead author of the study. Study of the Cooperative Institute for Environmental Science Research at the University of Colorado at Boulder. and colleagues.
"These bacteria must tolerate rapid fluctuations in temperature, long periods of stagnation or desiccation, followed by turbulent, high-shear flows, and low levels of nutrients and organic carbon typical of most drinking water sources. "
"In many cases, the bacteria associated with the showerhead must also be able to tolerate the residues of chemical disinfectants, including chlorinated compounds, which are often added to municipal drinking water to limit bacterial contamination.
"Most bacteria likely to become aerosolized and inhaled when using the shower are probably harmless. However, this is not always the case. "
"Bacteria in the genus mycobacterium are usually detected in showerhead biofilms and throughout the water distribution system. "
There are nearly 200 described species of NTM mycobacteria, defined as members of the genus that are not Mycobacterium tuberculosis or M. leprae – which respectively cause tuberculosis and leprosy.
Despite their importance, the diversity, distribution and environmental predictors of mycobacteria associated with the showerhead remain largely unresolved.
To fill these knowledge gaps, Dr. Gebert and his co-authors collaborated with citizen scientists to collect showerhead biofilm samples and associated water chemistry data from 656 households in the United States. United and in 13 European countries.
They found that showerheads often harbor many mycobacterial communities whose composition varies according to geographic location, chemical composition of water and water source.
Households receiving water treated with chlorinated disinfectants had a particularly high abundance of certain mycobacteria.
"By exploiting DNA sequencing technology, we were able to identify the bacterial species that lived in the silt of the showerhead and their abundance," said the study's authors.
"Mycobacteria were much more abundant in showerheads receiving municipal tap water than in those receiving well water, and more abundant in US households than in Europeans."
"These trends are probably due in part to differences in the use of chlorine disinfectants. Mycobacteria tend to be somewhat resistant to chlorine-based disinfectants used more frequently in the United States than in Europe. Thus, in Europe, other bacterial species could better develop and surpass the strains that cause the disease. "
"Shower head materials also seemed to affect the presence of mycobacteria in metal shower heads as well as in plastic ones. Plastic leaches certain chemicals that support various bacterial communities, possibly preventing mycobacteria from becoming too abundant.
When the researchers mapped where the potentially pathogenic mycobacteria were growing, the maps revealed "hot spots" roughly corresponding to areas where NTM lung disease is most prevalent – parts of southern California, southern California Florida and New York, highlighting the potentially important role of these leading bacteria in the transmission of the disease.
"Our results highlight the relevance of mycobacteria in showerhead biofilms for public health and advance our understanding of the dynamics of NCD transmission," they said.
"This study demonstrates that mycobacterial distributions in showerhead biofilms are often predictable from the chemistry of the focus and the chemistry of the water."
"The results will help develop strategies to reduce exposures to these emerging pathogens."
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Matthew J. Gebert et al. Ecological analyzes of mycobacteria in Showerhead biofilms and their relevance to human health. mbio, published online October 30, 1818; doi: 10.1128 / mBio.01614-18
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