IDEXX Colilert®-24 Enzyme Substrate Test System with Quanti-Tray® Sealer WPI200I

Overview

The IDEXX Colilert®-24 Enzyme Substrate Test System with Quanti-Tray® Sealer WPI200I is a standardized, regulatory-compliant solution for the simultaneous detection and quantification of total coliforms and Escherichia coli in drinking water, source water, and environmental water samples. Engineered for precision and reproducibility, this system implements IDEXX’s patented Defined Substrate Technology (DST)—a dual-enzyme chromogenic/fluorogenic assay based on the metabolic activity of β-galactosidase (for total coliforms) and β-glucuronidase (for E. coli). When present, coliform bacteria hydrolyze ortho-nitrophenyl-β-D-galactopyranoside (ONPG), yielding a yellow color change; E. coli further cleaves 4-methylumbelliferyl-β-D-glucuronide (MUG), emitting blue fluorescence under 365 nm UV light. This biochemical specificity eliminates interference from non-target heterotrophic microorganisms—enabling unambiguous, objective interpretation without confirmatory testing. The system is validated per U.S. EPA Method 1603 and included in the *Standard Methods for the Examination of Water and Wastewater* (23rd ed., Method 9223B). It complies fully with GB/T 5750.12–2006 (China’s Standard Methods for Drinking Water Examination) and supports GLP-aligned workflows in municipal, regulatory, and third-party laboratory environments.

Key Features

• Simultaneous detection of total coliforms and E. coli within 24 hours—no incubation extension or secondary confirmation required.
• Single-dose, lyophilized reagent format (Colilert®-24) eliminates media preparation, sterility concerns, and batch-to-batch variability.
• Integrated Quanti-Tray® Sealer WPI200I enables rapid, repeatable sealing of 51-well (Quanti-Tray®) or 97-well (Quanti-Tray®/2000) trays in ≤17 seconds per tray, with temperature-controlled heating rollers (180 ± 2 °C surface, 200 ± 10 °C internal).
• Robust mechanical architecture: 16 kg portable design (30 × 39 × 27 cm), CE-certified, rated for continuous operation of up to 40,000 seals, with noise emission <50 dB(A) and ambient operating range of –10 to 50 °C.
• Pre-programmed counting logic and automatic stop function ensure traceable, auditable seal integrity—zero leakage or puncture in >99.9% of sealed trays under ISO 17025–aligned validation protocols.
• Room-temperature shelf life of 12 months for Colilert®-24 reagents; all kits include lot-specific certificates of analysis, SNAP packaging, and expiration dating per ISO 9001 and ISO 14001 quality management requirements.

Sample Compatibility & Compliance

The Colilert®-24/WPI200I platform accepts raw, filtered, chlorinated, or low-turbidity water matrices—including tap water, groundwater, surface water, wastewater effluent, and recreational water. It is explicitly validated for 100 mL and 250 mL sample volumes, with demonstrated inhibition of up to 2 × 10⁶ CFU/mL heterotrophic bacteria per 100 mL and 5 × 10⁶ CFU/mL per 250 mL. Regulatory alignment includes: U.S. EPA Certification (Method 1603), Chinese National Standard GB/T 5750.12–2006, ISO 9308-1:2014 (water quality — enumeration of E. coli and coliform bacteria), and ASTM D6162–22 (standard test method for E. coli in water by membrane filtration). The system meets data integrity requirements under FDA 21 CFR Part 11 when paired with compliant LIMS integration and audit-trail-enabled software.

Software & Data Management

While the WPI200I sealer operates via embedded firmware (two-button interface: power and rewind), full traceability is achieved through optional integration with IDEXX’s Quanti-Tray® Reader Software or third-party LIMS platforms supporting HL7 or ASTM E1384 message formats. All seal cycles are timestamped and logged internally, including tray type (51-well or 97-well), seal count, thermal profile verification, and error codes. For laboratories under GLP or GMP oversight, the system supports IQ/OQ documentation packages, calibration logs (thermal verification every 6 months), and preventive maintenance records accessible via USB export. Raw fluorescence and colorimetric results from Colilert®-24 incubations are recorded manually or via digital UV readers compliant with ISO/IEC 17025 clause 7.7.

Applications

This system serves as the reference method for routine compliance monitoring in municipal water utilities, environmental health departments, and contract testing laboratories. It supports emergency response deployments (e.g., post-flooding or infrastructure failure), field-based surveillance in remote areas, and high-throughput screening in centralized labs processing >500 samples weekly. Validated use cases include: potable water safety verification per WHO Guidelines for Drinking-water Quality; source water vulnerability assessment; wastewater disinfection efficacy evaluation; beach water quality reporting; and validation of point-of-use treatment devices. Its quantitative MPN output (via Quanti-Tray® or Quanti-Tray®/2000) satisfies reporting thresholds for regulatory submissions to CNCA, MEP, or provincial CDC authorities.

FAQ

Is Colilert®-24 compatible with non-IDEXX quantitative trays?

No—only IDEXX-manufactured Quanti-Tray® and Quanti-Tray®/2000 trays are validated for use with Colilert®-24 and the WPI200I sealer due to precise dimensional tolerances and polymer formulation required for hermetic sealing.

Does the WPI200I require annual recalibration?

Thermal verification using NIST-traceable thermocouples is recommended every six months; full recalibration is not required unless physical damage or performance deviation (>±2 °C) is observed.

Can Colilert®-24 detect injured or stressed E. coli cells?

Yes—the DST assay detects enzymatically active cells only, providing a physiologically relevant viability endpoint superior to membrane filtration or culture-based methods that may recover non-viable organisms.

What is the minimum sample volume for accurate MPN estimation?

The validated range is 100 mL (Quanti-Tray®) or 250 mL (Quanti-Tray®/2000); smaller volumes reduce statistical confidence and are not supported under GB/T 5750.12–2006 or EPA Method 1603.

How is QC performed for each batch of Colilert®-24?

Each lot undergoes independent verification per ISO 11133:2014 using certified reference strains (E. coli ATCC 11775, Klebsiella pneumoniae ATCC 13883); QC documentation is supplied with every kit and archived for ≥5 years per GLP retention rules.