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Analytical Methods

INDICATOR BACTERIA CULTURE METHODS

Indicator bacteria are routinely measured by means of membrane-filtration or liquid broth most-probable number techniques.

  • Total coliforms, fecal coliforms, and Escherichia coli (E. coli) are in the total-coliform group.
  • Total coliforms are found in animal wastes, soils, on vegetation, and in industrial wastes.
  • Fecal coliforms are total coliforms that are able to grow at elevated temperatures and are often, but not always, associated with fecal contamination.
  • E. coli is one species in the fecal-coliform group, is a natural inhabitant of the gastrointestinal tract of warmblooded animals, and is used to provide direct evidence of fecal contamination.
  • Enterococci are a group of bacteria that have a different shape (the cells are round) and survival characteristics than total coliforms. They are generally associated with fecal contamination.
  • Clostridium perfringens (C. perfringens) is a spore-forming bacterium that is present in human and animal wastes, but in lower concentrations than standard bacterial indicators. Because spores are resistant to environmental stress, they may be useful surrogates for other stress-resistant pathogens.

Find out more about the analytical methods used for standard bacterial indicators.


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MI agar method for total coliforms and Escherichia coli

MI agar method for total coliforms and Escherichia coli


mENDO method for total coliforms.

mENDO method for total coliforms


Colilert method for total coliforms and Escherichia coli

Colilert method for total coliforms and Escherichia coli


Modified mTEC agar method for Escherichia coli

Modified mTEC agar method for Escherichia coli


mFC agar method for fecal coliforms

mFC agar method for fecal coliforms


mEI agar method for enterococci

mEI agar method for enterococci


Clostridium perfringens, using the mCP agar method

Clostridium perfringens, using the mCP agar method