What Is Growing in My Shower?

Dear Home Ec 101,

We keep getting these pale pinkish stains on the shower curtains and at the base of the tub…
Our neighbor has the same issue, and he thinks it’s metal in the Mt P. water supply.
Could it be mold?

I’ve found a weak bleach solution or most any bath cleaner completely fades the stains without much scrubbing - but the spots will return in less than a week if I don’t spray on a near-daily basis.

Signed,
~Pretty in Pink

Heather says:

You are right on target cleaning with a weak bleach solution.  The microorganism behind your bathroom cleaning quandary is Serratia marcescens and it loves damp environments.  The bacteria was once used for experimentation due to its coloration (it made it easy to track growth, even without a microscope).  However it has been found to cause urinary tract infections and rarely pneumonia.

Chlorine is an effective preventative and will wipe it out temporarily.  Unfortunately chlorine evaporates more quickly than water and eventually the airborne bacteria will reproduce in sufficient numbers to create the pink stain in showers, and in toilets that are used infrequently.  Remember to periodically clean your showerhead if you notice the telltale pink discoloration.