When a Colilert sample fluoresces, it is an indication of the presence of E. coli. The Colilert test uses a medium that contains nutrients and indicator compounds that specifically react with coliform bacteria.
In the presence of E. coli, the enzymes produced by these bacteria act on the compound in the reagent, resulting in fluorescence. This is a significant aspect of using the Colilert test, as it allows for the rapid and specific identification of E. coli, which is a crucial marker for fecal contamination in drinking water.
The other choices do not reflect the specific outcome of fluorescence in the Colilert test. While coliform bacteria are indeed detected in the test, they do not cause fluorescence; the test is designed specifically to highlight the presence of E. coli through this reaction. Salmonella, on the other hand, is not detected by the Colilert method, which focuses primarily on coliforms and E. coli. Therefore, the accurate identification of E. coli through fluorescence underlines its importance in evaluating water safety and quality.