What indicative property does the change of color in Colilert signify?

The change of color observed in the Colilert test indicates the presence of total coliform bacteria in a water sample. Colilert employs a substrate that, when metabolized by coliform bacteria, causes a visible color change, typically from yellow to a more intense shade. This reaction is due to the enzyme activity associated with total coliforms, reflecting fecal contamination and the general microbiological quality of drinking water.

It's important to understand that while this test is useful for indicating total coliform presence, it does not exclusively identify pathogenic organisms or all types of bacteria. Thus, the color change is specifically tied to the detection of total coliforms, making it a critical parameter in assessing water safety and microbiological quality.