Coliform Bacteria and E.coli

Accreditation: UKAS accredited for potable, process, swimming pool and hospital waters.

Sample volume: 100mls of sample is required.

Turnaround time: 24 hours or up to 72 hours if positive.

Expression of results: cfu/100mls


Coliforms are a group of bacteria that are widespread in the environment. They are found in the soil, in water, on plants and associated with animals. If these organisms are detected action should be taken to determine their source. Their presence indicates a failure of the system and that there is the potential for other more harmful organisms to be present.

E.coli (Escherichia coli) is a member of the coliform group. This organism is associated with the guts of warm-blooded animals – including humans. The significance of this organism is that it does not last very long outside the host, and therefore is an indicator of recent or current faecal contamination. E.coli is used as an indicator organism because it is generally non-pathogenic but indicates that faecal contamination is present, and hence there is the risk of enteric pathogens e.g. Salmonella, typhoid etc being present. Within a population the ratio of E.coli to pathogens is very high, so if action is taken when one E.coli is isolated the probability of a pathogen being present is very small.

If coliforms/E.coli are detected they may be derived from sewage contamination, but depending on the sample point they may also have come from animals or birds. If the sample point is a kitchen tap a coliform failure may be due to the tap being contaminated from soil following the preparation of vegetables. An unsatisfactory sample result from a toilet tap may be a result of the tap becoming contaminated by being touched with dirty hands.