Bathing water and E.Coli. Help!

Doug Rice drice at
Mon Aug 19 10:31:07 EST 1996

In article <aCMwRBAD1bFyEwLQ at> Gordon West <GordonWest at> writes:
>From: Gordon West <GordonWest at>
>Subject: Bathing water and E.Coli. Help!
>Date: Sat, 17 Aug 1996 13:38:27 +0100

>Everything seems to work fine but I am finding E. Coli everywhere
>including my garden pond but not tap water or the water butt. I suspect
>that my tests are showing positive when they shouldnt.
>These tests are for drinking water. Is there a more relaxed test for
>bathing water ?
>Does anyone know what the EEC directives are for bathing water quality ?
>Gordon West
>Isle of Wight, UK

As long as your broths and agars are sterile, you are probably isolating the 
organisms you are looking for.  It is a good idea to run negative controls to 
assure your media sterility.

I would recommend that you transfer positive LST tubes to tubes of EC broth 
(again with an inverted durham).  The EC broth is more selective and will 
eliminate the coliforms and allow the fecal coliforms to thrive.  Streaking 
positive EC tubes to EMB is still the best method.  If you have a green sheen 
colony on EMB you can pick it into a tube of LST containing MUG 
(4-methyl-B-D-glucuronate).  Within four hours E. coli will have broken the 
MUG molecule into a flourescent compound that glows blue under UV light (black 
flourescent light will work).

E. coli can be fairly common in bathing waters.  Lakes, ponds, and streams 
will also contain variable numbers of this bug due to geese, ducks, pets and 
livestock.  To help define the source of fecal contamination a fecal 
streptococci count should also be completed.  Human tend to have a lower 
percentage of strep than do most other mammals.
Good luck

Douglas A. Rice
CSU-Environmental Quality Laboratory Director
Applied microbiology of food, air, water and soil.
drice at
voice:  (970) 491-6503
"Moderation is for Monks, take big bites out of life."

More information about the Microbio mailing list