So you are in the shower soaping up and giving yourself a good scrubdown...

Gotta get rid of any lurking bacteria...

Yes, but what if, by simply showering, you were exposing yourself to a dangerous microbe?

Aha... you're talking about the shower head bacteria.

That's right! We've actually known that shower heads harbor microbes because they're warm, moist environments that are ideal for the formation of biofilms.

Biofilms are naturally occurring collections of microbes that adhere to many surfaces and form layers inside places such as pipes and showerheads.

But scientists were not able to identify the bacteria there because the samples were tough to culture in the lab. So, using some nifty molecular biology, researchers in this study isolated all the bacterial DNA present in 45 shower heads from 9 cities in the U.S.

They sequenced the DNA to identify the different types of bacteria present. Then they compared the results with genes of known bacteria and found many of the bacteria are common in soil and water.

What was unexpected was finding an unusually high number of the microbe Mycobacterium avium. It is normally not a threat to healthy people, but it is a threat to anyone whose immune system is compromised.

That's transplant recipients or anyone with chronic illnesses that interfere with their immune system.

The study showed twenty percent of showerheads sampled had mycobacterium avium.

But when researchers created a technique to specifically identify this microbe, nearly 80 percent of the showerheads tested positive.

The reason this bacterium is so common in showerheads is that it is resistant to chlorine, which water treatment plants use to purify our drinking water. In fact, the study found chlorine actually made it thrive.

Hey, maybe Mycobacterium avium caused Hamlet to say "will these hands never be clean"...