A common indicator of the sanitary quality of foods and water is the presence of Coliform bacteria. These are rod-shaped, Gram-negative, non-spore forming bacteria. They are found in a wide range of environments from aquatic, soil or vegetation – most well known are their presence in the faeces of warm-blooded animals. Although they themselves don’t often cause serious illness they are an indicator of other pathogenic organisms of faecal origin which may be present in a water sample.
Palintest have created a quick and simple test to detect the presence of the bacteria in liquid samples. 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 in drinking water, surface and source water samples. Positive samples are detected by a visible colour change.
The test is based on the detection of two enzymes ß-glucuronidase and R-galactosidase, which are characteristic of E.coli and the coliform groups, respectively. Colitag detects Total Coliforms using the chromogenic substrate ortho-nitrophenyl-ß-D-galactopyranoside (ONPG). Upon hydrolysis by ßgalactosidase, ONPG produces a distinct yellow colour, confirming the presence of coliforms in the sample. For detection of E.coli, Colitag utilizes the fluorogenic enzyme substrate 4-methylumbelliferyl-ß-D-glucuronide (MUG). Upon hydrolysis by ß-glucuronidase, MUG releases 4-methylumbelliferone. This reaction byproduct fluoresces when exposed to UV light. The ß-glucuronidase enzyme is specific to E.coli and observation of fluorescence differentiates this organism from
other members of the coliform group.
What is the method?
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. In addition, if any E.coli bacteria are present in the sample, a bright blue fluorescence is emitted when the sample is subjected to long wavelength (366 nm) ultraviolet (UV) light placed 3 -4 cms away.
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