Coliform bacteria are the commonly-used bacterial indicator of sanitary quality of foods and water. They are defined as rod-shaped Gram-negative non-spore forming organisms that ferment lactose with the production of acid and gas when incubated at 35-37°C. Coliforms are abundant in the feces of warm-blooded animals, but can also be found in the aquatic environment, in soil and on vegetation. In most instances, coliforms themselves are not the cause of sickness, but they are easy to culture and their presence is used to indicate that other pathogenic organisms of fecal origin may be present. Fecal pathogens include bacteria, viruses, protozoa or parasites.

Typical generally include:

• Citrobacter
• Enterobacter
• Escherichia
• Hafnia
• Klebsiella
• Serratia
• Yersinia.

Escherichia coli (E. coli), a rod-shaped member of the coliform group, can be distinguished from most other coliforms by its ability to ferment lactose at 44°C, and by its growth and colour reaction on certain types of culture media. Unlike the general coliform group, E. coli are almost exclusively of faecal origin and their presence is thus an effective confirmation of faecal contamination. Typically, E. coli are about 11% of the coliforms in human faeces.

Untreated organic matter that contains fecal coliform can be harmful to the environment. Aerobic decomposition of this material can reduce dissolved oxygen levels if discharged into rivers or waterways. This may reduce the oxygen level enough to kill fish and other aquatic life. Reduction of fecal coliform in wastewater may require the use of chlorine and other disinfectant chemicals. Such materials may kill the fecal coliform and disease bacteria. They also kill bacteria essential to the proper balance of the aquatic environment, endangering the survival of species dependent on those bacteria. So, higher levels of fecal coliform require higher levels of chlorine, threatening those aquatic organisms.

Fecal coliform, like other bacteria, can usually be killed by boiling water or by treating with chlorine. Washing thoroughly with soap after contact with contaminated water can also help prevent infections. Gloves should always be worn when testing for fecal coliform. Municipalities that maintain a public water supply will typically monitor and treat for fecal coliforms.

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