Bacteria (Prescence/Absence)

Coliforms and E.coli

We offer the EPA-approved IDEXX Colilert test, which simultaneously detects both total coliforms and E. coli specifically, within 24 hours. This precise test can detect a single viable coliform or E. coli per sample. One 100 mL test sample is inoculated into a single culture bottle to obtain qualitative information on the presence or absence of coliforms and E.coli, through the presence or absence of lactose fermentation. This test is based on the principle that coliforms and other pollution indicator organisms should not be present in a 100 mL water sample.

The Colilert Test uses proprietary Defined Substrate Technology (DST) to simultaneously detect total coliforms and E. coli. Two nutrient-indicators, ONPG and MUG, are the major sources of carbon in Colilert and can be metabolized by the coliform enzyme β-galactosidase and the E. coli enzyme β-glucuronidase, respectively.

As coliforms grow in the Colilert Test, they use β-galactosidase to metabolize ONPG and change it from colorless to yellow. 

E. coli use β-glucuronidase to metabolize MUG and create fluorescence. Since most non-coliforms do not have these enzymes, they are unable to grow and interfere. The few non-coliforms that do have these enzymes are selectively suppressed by the Colilert Test’s specifically formulated matrix.


Like Colilert, we offer the EPA-approved IDEXX Enterolert Test. This official test method (ASTM D6503-19) covers a simple procedure for the detection of enterococci in water and wastewater. The patented Defined Substrate Technology (DST) nutrient indicator detects enterococci in a 100 mL sample after incubation within 24 hours. Enterolert, utilizes a nutrient indicator that fluoresces when metabolized. The presence of this microorganism in water is an indication of fecal contamination and the possible presence of enteric pathogens.