Coliform Bacteria

Coliform bacteria (coliforms) are a large group of various species of bacteria including Citrobacter, Enterobacter, Escherichia, and Klebsiella. They include both fecal coliform bacteria of the family Enterobacteriaceae (bacteria that are found naturally in the intestines of warm-blooded animals) and non-fecal coliform bacteria.

Coliforms may be aerobes or facultative anaerobes that are non-spore-forming, gream-negative, rod-shaped bacteria. They get their energy by fermenting lactose, a sugar. During fermentation, the sugar is converted into energy, a gas, and an acid. These bacteria have an enzyme called galactosidase necessary to break down sugar. E. coli produces the enzyme glucuronidase in addition to galactosidase.

Coliform bacteria are indicator organisms. Their normal habitat is mammalian gut as well soil and warm water. Many coliform bacteria do not cause disease. However, if coliforms are detected in drinking water it indicates that there may be more dangerous bacteria also present in the supply, such as Salmonella and Escherichia coli (E. coli). Infection with these bacteria may lead to severe diarrheal disease.1 Besides fecal coliforms, other organisms that serve as indicators of microbial contamination and potential health risks include Enterococcus and Streptococcus3.

Safety Standards of Drinking and Recreational Water

Water authorities check waterways to be sure that total coliform (TC) and fecal coliform (FC) fall within safe exposure levels with safe standards being 1 TC bacterial colony per 100 ml drinking water and 200 FC bacterial colony for swimming.2 Most often TC found in the environment are 10 times greater than FC. Water monitoring for coliforms is also necessary to determine if the water is suitable for eating fish and harvesting filter feeders such as clams, oysters and scallops. Filter feeders tend to concentrate contaminants including bacteria which continue to grow in them. Consumption of oysters with pathogenic bacteria or viruses has resulted in outbreaks of gastrointestinal disease.5

ScallopScallops and other filter feeders tend to concentrate coliform bacteria which continue to grow in them.

Waterborne Diseases Linked to Presence of Coliforms

Example of waterborne diseases for which coliforms serve as indicators:

  • Shigella spp. - shigellosis
  • Salmonella typhimurium - salmonellosis
  • Salmonella typhi - typhoid fever
  • Escheriachia coli - gastroenteritis
  • Campylobacter jejuni - gastroenteritis
  • Vibrio species - gastroenteritis
  • Pseudomonas - infections
  • Legionella - Pontiac fever
  • Leptospira - leptospirosis
  • Hepatitis A virus - hepatitis
  • Norwalk-like agent (virus) - gastroenteritis
  • Rotaviruses - gastroenteritis
  • Polioviruses - poliomyelitis
  • Giardia lamblia (protozoan) - giardiasis
  • Cryptosporidium (protozoan) - cryptosporidiosis
  • Entamoeba histolytica (protozoan) - amebiasis
  • Ascaris spp. (helminth ) - ascariasis
  • Ancylostoma spp. (helminth ) -
  • Necator spp. (helminth ) - anemia
  • Ascaris spp. (helminth ) - anemia
  • Trichuris spp. (helminth ) - gastroenteritis4

Alternative microbial indicators have been evaluated as indicators of fecal pollution (human and nonhuman) such as Clostridium perfringens, Streptococcus bovis, Rhodococcus coprophilus, sorbitol-fermenting bifidobacteria (human fecal pollution), Coliphages, and Staphylococcus aureus.


  1. Facilities Manager's Desk Reference. Jane M. Wiggins
  2. Environmental Science Experiments. Pamela Walker, Elaine Wood
  3. Wastewater pathogens. Michael H. Gerardi, Melvin Charles Zimmerman
  4. Changing land use patterns in the coastal zone: managing environmental quality in rapidly developing regions. Gary S. Kleppel
  5. Handbook of water analysis. Leo M. L. Nollet



Home Contact RSS