E.Coli in Drinking Water
E.Coli in Drinking Water - This short paper covers
issues associated with E.coli in drinking
water. E.coli or Escherichia coli are bacteria that normally
live in the intestines of humans and animals. Although, most strains
of these bacteria are harmless, several are known to produce toxins
that can cause diarrhea. One particular E.coli strain called O157
can cause severe diarrhea and kidney damage.
Why this note?
There have been a number of media reports on
outbreaks of diarrhoeal illnesses caused by the E.coli O157
bacteria, including reports from North America involving water
supplies. The purpose of this note is to provide reassurance
about the safety of public water supplies in England and Wales.
Why the concern?
In contrast to the harmless E.coli strains normally found
in the gut of all warm-blooded animals, the O157 strain produces
a potent toxin. This causes severe diarrhoea and in some cases
renal failure and death. Toxigenic E.coli, including O157
and other strains, are carried by 10-15% of healthy ruminants,
including cattle, sheep, goats and deer. The bacteria may
be transmitted to humans by consumption of raw or undercooked
meats, or by faecal contamination of foodstuffs or water supplies.
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E-coli
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How does this affect drinking water?
Because E.coli are always present in human and animal faeces in
very high numbers, they are used as an indicator of faecal pollution
in the microbiological surveillance of drinking water. On very rare
occasions, low numbers of Ecoli are detected in drinking water.
This does not indicate that O157 is present, or that there is an
immediate risk to health. Detection of Ecoli does however necessitate
an immediate investigation of the water supply system in order to
identify and eliminate the source of pollution.
How is E.coli dealt with?
All Ecoli bacteria are rapidly inactivated by chlorine and other
disinfectants used in the treatment of public water supplies. Drinking
water related cases of infection are invariably associated with
unchlorinated supplies or with systems where there is poor maintenance
or operation of disinfection systems. In the UK, no O157 infections
have been associated with public water supplies. Some cases have
occurred where consumers use private water supplies that are not
disinfected.
© Crown copyright 2001 Reproduced courtesy
of the Drinking Water Inspectorate
dwi_enquiries@detr.gov.uk
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