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One technique for detecting indicator organisms is the use of chromogenic compounds, which are added to conventional or newly devised media used for isolation of the indicator bacteria. These chromogenic compounds are modified to change color or fluorescence by the addition of either enzymes or specific bacterial metabolites.
Similar to how there are various types of indicator organisms, there are also various types of indicator bacteria. The most common indicators are total coliforms, fecal coliforms, E. coli, and enterococci. [2] The presence of bacteria commonly found in human feces, termed coliform bacteria (e.g. E. coli), in surface water is a common indicator ...
Coliform bacteria include genera that originate in feces (e.g. Escherichia, Enterobacter, Klebsiella, Citrobacter). The fecal coliform assay is intended to be an indicator of fecal contamination; more specifically of E. coli which is an indicator microorganism for other pathogens that may be present in feces.
Coliform bacteria are defined as either motile or non-motile Gram-negative non-spore forming bacilli that possess β-galactosidase to produce acids and gases under their optimal growth temperature of 35–37 °C. [1] They can be aerobes or facultative aerobes, and are a commonly used indicator of low sanitary quality of foods, milk, and water. [2]
Lactose fermenters turn red or pink on MacConkey agar, and nonfermenters do not change color. The media inhibits growth of gram-positive organisms with crystal violet and bile salts, allowing for the selection and isolation of gram-negative bacteria. The media detects lactose fermentation by enteric bacteria with the pH indicator neutral red. [2]
A biological indicator is also the name given to a process for assessing the sterility of an environment through the use of resistant microorganism strains (e.g. Bacillus or Geobacillus). [5] Biological indicators can be described as the introduction of a highly resistant microorganisms to a given environment before sterilization , tests are ...
The common feature of all these routine screening procedures is that the primary analysis is for indicator organisms rather than the pathogens that might cause concern. . Indicator organisms are bacteria such as non-specific coliforms, Escherichia coli and Pseudomonas aeruginosa that are very commonly found in the human or animal gut and which, if detected, may suggest the presence of se
Koser found that citrate metabolism could be an indicator for bacteria found in natural environments. Additionally, citrate could be used to distinguish bacterial coilforms found in soil, and aquatic environments, such as Enterobacteiacea, and coilforms with fecal contamination. It was found that coilforms without fecal contamination grew ...