Mycobacteria, especially Mycobacterium avium, are a well-known danger for people with lung disease and those suffering immune deficits such as HIV/AIDS. However, otherwise healthy people exposed to hot-water aerosols are also being sickened by M. avium which is why Norman Pace and his colleague Leah Feazel at the University of Colorado in Boulder began searching showerheads for reservoirs of these potential pathogens.
Warm, moist showerheads encourage microbial growth
Showerheads provide an ideal environment for microorganisms, especially those that form biofilms (communities of microbes that adhere to surfaces). M. avium is a notorious chlorine-resistant, biofilm-forming opportunistic pathogen. Thus the scientists swabbed their way through urban and rural showerheads and got results that surprised even them: there was a 100-fold greater abundance of mycobacterial sequences in the showerheads used by city dwellers versus those located in rural areas.
Mycobacteria apparently thrive in chlorine-treated municipal water which kills off most of their competitor-microbes. Indeed, when the scientists tried to clean one shower head with bleach, the mycobacteria within –in this case M. gordonae—increased in relative abundance.
Read more about the mycobacteria that might be sharing your shower in Microbe Magazine.