The Colitag System is a breakthrough in Coliform testing. The test enables the simultaneous detection, identification and confirmation of total coliforms and E.coli in 24 hours or less.

The examination of water for microbial pollution is a major health undertaking. Drinking water supplies, swimming pools and spas are all regularly monitored for the indicator organism Escherichia coli (E.coli). Currently there are two accepted methods in use – Multiple Tube fermentation (MTF) and Membrane Filtration (MF). Both are designed to enumerate the secondary indicator group, total coliforms.

There are several drawbacks to these current methods of bacteriological testing – in particular the time taken to generate confirmed positive results, usually two to five days. Moreover, the subjective nature of interpreting results, the lengthy and labour intensive procedure involved and the susceptibility to interference by non-coliform heterotrophic bacteria, all detract from these methods.

The Coliform Testing System

A simple, reliable technique is required which eliminates these drawbacks and enables the rapid, confirmed enumeration of both total coliforms and more importantly, E. coli.

Colitag is a pre-dispensed dry blended reagent formulation containing salts, nitrogen and carbon sources and specific indicator/nutrients for total coliform and E. coli. Positive samples are detected by a visible colour change.

Performing the Coliform test is simple. The reagent is supplied in pre-measured dosage tubes for dispensing into sterile containers. Simply fill a sterile tube to the level, mix and then incubate at 35 ° C. The formation of a yellow colour in 24 hours or less indicates the presence of total coliforms. Positive tubes are then checked for the presence of E.Coli by looking for fluorescence under UV light.

The Colitag™ Principle

In theory, coliforms are organisms that are closely related to E.Coli. Since E.Coli is present in the digestive tract, and not in the general environment, this organism is used as an indicator of Faecal contamination in water or food samples. Colitag™ incorporates a three stage process for definitive coliform testing.

• ONPG test indicates the presence of beta-galactosidase (unique characteristic of of coliform in general; coliforms utilise lactose to produce gas or acid.
• MUG test to identify the presence of beta-glucuronidase (unique characteristic of E.Coli). But one third of E.Coli are MUG-negative, meaning they do not have this enzyme in their metabolic pathway.
• Indole test – a second test specific for E.Coli, in case the MUG fails to identify the presence of E.Coli

You cannot rely on the MUG test alone to identify the E.Coli in a sample. The solution is to incorporate the Indole test in the media, but since lactose would interfere with the Indole test, ONPG is substituted.

A single inoculation can be performed with less than 2 minutes hands-on time. Conclusive results are available in 24 hours or less without the need for confirmatory tests or sub-cultures.

This breakthrough has been made possible by recent developments in defined substrate technology. This enables the simultaneous detection of total coliforms and E.coli by a simple colour reaction. Simply add water, incubate and read. Total coliforms are identified by a yellow colour in the incubated sample, E.coli is confirmed by fluorescence observed under UV light.

Colitag™ is a Trademark of CPI International Inc.