Bacteria May Lurk on Your Showerhead
Researchers Say Some Microorganisms on Showerheads May Be Small Enough to Be Inhaled
By
Kathleen Doheny
WebMD Health News
Reviewed By
Louise Chang, MD
Sept. 14, 2009 -- Showerheads in your home may harbor potentially infectious
bacteria and enrich their growth, according to a new study.
Researchers from the University of Colorado sampled gunk, which they call
biofilm, from 45 germy showerheads in nine U.S. cities, then analyzed the
ribosomal RNA gene sequences from the swab samples to figure out exactly what
microorgamisms lurked there. They compared them with swabs from water before it
entered the showerhead.
"What we show is the showerhead biofilm contains Mycobacterium avium
concentrations relative to other organisms 100-fold higher than in water
[before it comes out of the showerhead]," says Norman R. Pace, the study's
senior author and distinguished professor of molecular, cellular and
developmental biology at the University of Colorado, Boulder.
The study is part of a larger effort the team is involved in, focusing on
the microbiology of the indoor environment and how it may contribute to
illness. The current study received funding from the National Institute of
Occupational Safety and Health and the Alfred P. Sloan Foundation.
"We don't know a whole lot about Mycobacterium avium prevalence,"
Pace tells WebMD. "It's hard to detect and largely ignored.''
Researchers do know that infections caused by the Mycobacterium avium
complex occur often in patients with conditions that hamper cellular immunity
such as AIDS and in patients who have chronic lung disease such as emphysema,
according to the Infectious Diseases Society of America.
But the infections are not reported nationally to the CDC, whose researchers
suspect the infections are probably environmentally acquired.
Pace says his previous studies of swimming pools and their biofilms, which
commonly include Mycobacterium avium, got him to think about showers and
germy showerheads, leading to the current study, which is published online in
the journal PNAS Early Edition.
Searching for Germs
Pace's team swabbed the interior surfaces of the 45 showerheads from nine
U.S. cities, including New York City, and eight others in Colorado, North
Dakota, Illinois, and Tennessee.
Though they found varied microorganisms, Pace says that particularly
striking was the non-tuberculous mycobacteria such as Mycobacterium
avium. ''Exactly how much Mycobacterium is coming out during the shower is
not clear," he says, since the swab was taken from the showerhead itself.
Some of the particles coming from showerheads, he says, are tiny enough to
be inhaled into the airways.
In the paper, the researchers write: "We conclude that showerheads may
present a significant potential exposure to aerosolized microbes, including
documented opportunistic pathogens."
Paces adds that the potential health risk needs more research, particularly
in patients with compromised immune or pulmonary systems, such as those with
AIDS or emphysema.
The new study gives a better sense of exactly how germy the showerheads are,
Pace says, than earlier research, which focused on culture-based techniques
rather than genetic sequencing.
Until more research is done, Pace suggests inspecting your showerhead. If
it's full of crusty crud, he says, "Get a new showerhead." He prefers all metal
models to plastic, saying that plastic is more conductive to microorganisms
sticking.
His hygiene advice: While a normal, healthy person need not be concerned, he
says those with immune system or lung problems may want to take baths instead
of showers.
Not so fast on ditching your shower, says Aaron E. Glatt, MD, a spokesman
for the Infectious Diseases Society of America and president and CEO of the New
Island Hospital in Bethpage, N.Y., who reviewed the study for WebMD.
"Nobody should be changing their personal hygiene preferences based on this
article," Glatt says.
The research, he says, is a basic science investigation. "Before a basic
science study can be translated to practical clinical advice, there needs to be
a lot of additional scrutiny. Mycobacterium avium and the other
non-tuberculous mycobacteria are ubiquitous," he says.
"For healthy people, they don't represent a significant pathogen," he says.
"For the immunocompromised, he says, they are more of a concern. Still, he
says, more study is needed to see if the findings have importance clinically
and would warrant new advice to people.
Meanwhile? "Cleaning the showerhead is a reasonable thing to do."
SOURCES: Norman Pace, PhD, distinguished professor of molecular, cellular and developmental biology, University of Colorado, Boulder.
Aaron E. Glatt, MD, spokesman, Infectious Diseases Society of America; president and CEO, New Island Hospital, Bethpage, N.Y.
Feazel, L. PNAS Early Edition, September 2009.
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