Product Description



  • U.S. EPA-approved, 24-hour test for drinking, wastewater and source waters.
  • International approvals include AOAC, IBWA, and EBWA.
  • Millions of tests performed worldwide every year.

  • Ease of use simplifies training.
  • Unit-dosed packaging eliminates media preparation.
  • No repeat testing due to clogged filters or heterotrophic interference.
  • Quality Control (QC) procedure can be done in 15 minutes.

  • Less than 1 minute of hands-on time.
  • Detects coliforms and E. coli simultaneously in 24 hours or less.
  • No confirmations needed.
  • No glassware cleaning or colony counting.
  • Identifies E. coli specifically, eliminating unnecessary public notification due to non-target organisms.
  • Suppresses up to 2 million heterotrophs per 100 mL.
  • Eliminates the subjective interpretation found in traditional methods.
  • Detects a single viable coliform or E. coli per sample.
  • Minimizes evening and weekend work.
  • Up to 12-month shelf life at room temperature.
  • Can be used for presence/absence (P/A) or quantification testing with Quanti-Tray and Quanti-Tray/2000.
  • The Colilert Test is also available predispensed in 10mL Most Probable Number (MPN) tubes.


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.

This approach is different from traditional media, which provide a nutrient-rich environment that supports the growth of both target organisms and nontargets. When nontargets grow and mimic target organisms, false positives occur. Growth of nontargets can also suppress target organisms and give false negatives in traditional media. To suppress nontargets, traditional media often include high levels of salts, detergents, or other selective agents that may inadvertently suppress target organisms and give further false negatives.

Only IDEXX reagents have been validated and approved for use with Quanti-Tray and Quanti-Tray/2000.


Step 1

Add reagent to sample and incubate at 35°C±0.5°C for 24 hours.

Step 2

Read results:

  • Colorless = negative
  • Yellow = total coliforms
  • Yellow/fluorescent = E. coli


Step 1

Add reagent to sample.


Step 2

Pour into Quanti-Tray (counts from 1–200) or Quanti-Tray/2000 (counts from 1–2,419).


Step 3

Seal in Quanti-Tray Sealer and place in 35°C ± 0.5°C incubator for 24 hours (in other countries, the temperature requirement may be different per regulatory requirements).


Step 4: Quanti-Tray

Quanti-Tray—Read results:

  • Yellow wells = total coliforms
  • Yellow/fluorescent wells = E. coli
  • Count positive wells and refer to MPN table

Step 4: Quanti-Tray/2000

Quanti-Tray/2000—Read results:

  • Yellow wells = total coliforms
  • Yellow/fluorescent wells = E. coli
  • Count positive wells and refer to MPN table

Product Information

Colilert Test (20-test pack)
Product Number: 98-12972-00
Catalog Number: WP020I

Colilert Test (100-test pack)
Product Number: 98-27163-00

Catalog Number: WP100I

Colilert Test (200-test pack)

Product Number: 98-12973-00
Catalog Number: WP200I

10mL Colilert Test (100-test pack)
Product Number: 98-14770-00

Catalog Number: W100I

10mL Colilert Test (200-test pack)
Product Number: 98-14771-00

Catalog Number: W200I

Snap pack and Quanti-Tray bundles are available.

How to use


Learn how to use the Colilert test

Wistia video thumbnail

There are no reviews yet.

Only logged in customers who have purchased this product may leave a review.