What is the most commonly used method in labs for testing total coliform and E. coli?

The most commonly used method in laboratories for testing total coliform and E. coli is the Colilert test. This method utilizes a specific nutrient indicator system that allows for the simultaneous detection and quantification of both total coliforms and E. coli in water samples.

The Colilert test involves adding a reagent to water samples, which can then be incubated. If coliforms are present, the sample will change color and produce a fluorescent signal under UV light. This dual response provides a straightforward way to not only confirm the presence of these bacteria but also to quantify their levels. The ease of use, rapid results, and precision in detecting these common indicators of water quality contribute to the popularity of the Colilert method in routine water testing protocols.

Other methods, such as membrane filtration and multiple-tube fermentation, are also valid techniques for testing bacterial contamination, but the Colilert test has gained preference in many lab settings due to its efficiency and clarity in results.