Water, Sewage & Effluent July August 2018 | Page 30

Escherichia coli:
indicator of bacteriological
quality of water
Faecal coliform bacteria in a waterway is an indication of sewage – and of
the possible presence of other pathogenic organisms.
By Anna Loots
Escherichia coli (also known as E. coli)
is a Gram-negative, anaerobic, rod-
shaped, coliform bacterium of the genus
Escherichia that lives in large numbers
in the intestines of mainly warm-blooded
organisms. Most E. coli strains are
harmless, but others cause serious food
poisoning in their hosts. One such strain is
Escherichia coli O157: H7, mainly present
in the digestive tracts of cattle.
The harmless strains are part of the
normal microbiota of the gut, and can
benefit their hosts by producing vitamin
K2, and also preventing colonisation of
the intestine with pathogenic bacteria.
E. coli is expelled into the environment
within faecal matter.
The major route through which
pathogenic strains of the bacterium
cause disease E. coli and other facultative
anaerobes, are faecal/oral transmission.
Cells may survive outside the body
for a limited amount of time, which
make them potential indicators of
organisms to test environmental
samples for faecal contamination. A
growing body of research, though, has
examined environmentally persistent
E. coli, which can survive for extended
periods outside a host.
E. coli is the most widely studied
prokaryotic model organism.
Swimming in water with high levels of faecal coliform
bacteria increases the chance of developing illness
from pathogens entering the body through the
mouth, nose, ears, or cuts in the skin.
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Water Sewage & Effluent July/August 2018
Background