I came across this little critter while doing some research on proteus organisms. Note where it is commonly found. It is a nasty little thing, especially for one with diminished immune response.
http://en.wikipedia.org/wiki/Proteus_vulgaris

Note where it is primarily found.

A tangential item of interest, it seems heliobacter pylori, accepted as a common cause of indigestion and ulcers, can be water-borne. May cause more problems than originally considered.