Study: Showerhead Bacteria Associated with Lung Disease

A new study has discovered a correlation between high levels of pathogenic mycobacteria on showerheads and nontuberculous mycobacterial (NTM) lung infections. 

According to the researchers, while most bacteria found in showerheads and other household waterways are innocuous, some are potential pathogens. Among these are genus Mycobacterium that lead to nontuberculous mycobacterial lung disease—which the researchers call an increasing public health concern in the United States and other developed countries. 

Researchers studied biofilm samples from 656 showerheads in the U.S. (n = 606) and Europe (n = 50) and evaluated the bacteria present using a cultivation-independent 16S rRNA gene sequencing approach. They found that, on average, the most bacteria found in the samples were members of the genus MycobacteriumMycobacterium genus represented an average of 13.5% of overall 16S rRNA gene reads—but presence varied greatly between samples, ranging from 0% (no presence of mycobacteria) to > 99% of bacterial 16S rRNA gene reads. In 238 samples, Mycobacterium comprised > 10% of 16S rRNA gene reads. 

American showerheads had, on average, 2.3 times the presence of Mycobacterium genus taxa than European ones. In the U.S., mycobacteria incidence was greater in homes with water from municipal water treatment plants than homes using well water. 

“Water treatment plants in the United States must maintain excess chlorine-based disinfectant within the distribution system, and we found, as expected, that those homes on municipal water had measured total chlorine concentrations 15 times higher, on average, than homes with well water,” the researchers wrote. 

Researchers also observed “significant correlations between the abundances of these mycobacteria found in showerheads sampled across the United States and NTM lung disease prevalence.” 

Regions with a high number of NTM lung disease patients (including Florida, Hawaii, southern California, and the mid-Atlantic states) were the same ones with significant potentially pathogenic mycobacteria presence on showerheads. 

The researchers wrote, “More generally, our results highlight the relevance of understanding how shifts in household water sources (i.e., from well to municipal water sources) and water treatment practices may be contributing to the apparent rise in NTM infections in U.S. and European populations,” also noting that their study highlights “the important role of showerheads in the transmission of NTM infections.” 

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Source: mBio