Enumeration of coliform bacteria and Escherichia coli
Enumeration of coliform bacteria and Escherichia coli
Enumeration of coliform bacteria and Escherichia coli
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ENUMERATION OF COLIFORM BACTERIA AND<br />
ESCHERICHIA COLI BY MEMBRANE<br />
FILTRATION<br />
SCOPE OF DOCUMENT<br />
The method described is applicable to the enumeration <strong>of</strong> <strong><strong>coli</strong>form</strong> <strong>bacteria</strong> <strong>and</strong> <strong>Escherichia</strong> <strong>coli</strong> in<br />
water samples intended for human consumption <strong>and</strong> in pool waters by the membrane filtration<br />
technique. It may be used for environmental <strong>and</strong> recreational water samples but not for designated<br />
bathing waters sampled under the bathing water regulations 2 . These samples are analysed using<br />
methods detailed by the Environment Agency.<br />
INTRODUCTION<br />
Background<br />
Coliform <strong>bacteria</strong> are widely regarded as the most reliable microbiological indicator <strong>of</strong> water quality.<br />
They are found in the human <strong>and</strong> animal intestine <strong>and</strong> may serve as indicators <strong>of</strong> potential faecal<br />
pollution but may also be environmental in origin. ‘Faecal <strong><strong>coli</strong>form</strong> <strong>bacteria</strong>’ <strong>and</strong> E. <strong>coli</strong> are only found in<br />
human <strong>and</strong> animal intestines <strong>and</strong> tests for their presence in water are necessary to confirm that pollution<br />
is <strong>of</strong> human <strong>and</strong>/or animal origin. The term ‘faecal <strong><strong>coli</strong>form</strong>’ is not precise <strong>and</strong> is consequently not used<br />
in this National St<strong>and</strong>ard Method (NSM). In the context <strong>of</strong> water microbiology in the United Kingdom<br />
faecal <strong><strong>coli</strong>form</strong> <strong>bacteria</strong> are regarded as being E. <strong>coli</strong>.<br />
Coliform <strong>bacteria</strong> <strong>and</strong> E. <strong>coli</strong> are sensitive to the disinfection processes used in water treatment <strong>and</strong> do<br />
not usually multiply in water particularly in temperate zones. These organisms should not be present in<br />
a 250 mL sample <strong>of</strong> mineral waters or drinking waters in bottles <strong>and</strong> containers or 100 mL for other<br />
waters <strong>of</strong> potable quality 3-11 .<br />
This method is based on the method described in the Microbiology <strong>of</strong> Drinking Water 2002 document 12 .<br />
ENUMERATION OF COLIFORM BACTERIA AND ESCHERICHIA COLI BY MEMBRANE FILTRATION<br />
Issue no: 4.1 Issue date: 03.10.07 Issued by St<strong>and</strong>ards Unit, Evaluations <strong>and</strong> St<strong>and</strong>ards Laboratory in conjunction with the<br />
Regional Food, Water <strong>and</strong> Environmental Coordinators Forum Page 5 <strong>of</strong> 15<br />
Reference no: W 2i4.1<br />
This SOP should be used in conjunction with the series <strong>of</strong> SOPs from the Health Protection Agency<br />
www.evaluations-st<strong>and</strong>ards.org.uk<br />
Email: st<strong>and</strong>ards@hpa.org.uk
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