What color does Colilert change to in the presence of total coliform?

Colilert is a widely used test that determines the presence of total coliform bacteria and E. coli in drinking water samples. In the presence of total coliform, the Colilert medium undergoes a color change to yellow due to the enzymatic reaction of the coliform bacteria with the substrate. This substrate releases a chromogenic compound that becomes yellow when hydrolyzed, indicating the presence of coliforms.

Understanding the color change is crucial for laboratory analysts as it directly indicates whether the water sample meets safety standards for coliform levels, which is vital for public health. The clarity of this test helps in quickly assessing water quality, facilitating timely actions if contamination is detected.