Detection of Coliforms
Fluorocult® media were introduced in 1986 to shorten the time to result and to reduce the costs per test. The principle of these Fluorocult® media is that an enzyme which is characteristic of the target organism splits a fluorogenic substrate into a sugar or amino acid component and methylumbelliferone. UV light makes methylumbelliferone visible and is thus used to evaluate fluorogenic culture media. The substance’s typical blue fluorescence indicates a positive result. The substrate MUG (4-methylumbelliferyl-β-D-glucuronide) is added to traditional media for the detection of Escherichia coli or E.coli O157. The substrate methylumbelliferylphosphate was introduced for the rapid detection of Clostridium perfringens.
Readycult® media enable testing for enterococci and coliforms / E.coli. They include KOVAC’s indole reagent to additionally confirm the presence of E.coli. These media are supplied in a ready-to-use snap-pack format for fast and easy preparation. Results are obtained within 18 to 24 hour of incubation. Any color change of the broth to blue-green, even if only in the upper section, is a positive result.
Readycult® Coliforms 100 is a rapid presence / absence test for the simultaneous detection of total coliforms and Escherichia coli in drinking water. Readycult® is supplied as a premeasured, single use, sterilized packet of media. If coliforms are present in the water sample, their β-galactosidase enzymes cleave the colorless X-GAL so that the culture medium changes its color from yellow to blue-green. If E.coli is present among the coliforms, their β-glucuronidase enzymes cleave the contained substrate MUG (4-methylumbelliferyl-β-D-glucuronide), producing blue fluorescence which is visible under UV light (366 nm). This MUG reaction is not totally specific for E.coli. A few other species of bacteria can also cleave MUG (mug positive), and certain strains of E.coli are known to be MUG-negative. A biochemical test for E.coli can be performed directly in the sample by adding KOVAC's indole reagent. The reagent reacts with indole to display a red ring in the presence of E.coli, due to the ability of this organism to produce indole from the amino acid tryptophan. A positive result proves the presence of E.coli with 99% certainty and eliminates the need for additional 24-48 hour confirmation steps. Readycult® Coliforms is also available as Readycult® Coliforms 50 for 50 ml samples.
Readycult® Enterococci 100 is a selective enrichment broth for the detection of Enterococcus and group D Streptococcus species in bacteriological water examinations. The peptone mixture guarantees rapid growth of enterococci. Sodium-azide largely inhibits any accompanying flora, especially Gram-negative bacteria. In a reaction that is stimulated by selected peptones, the chromogenic substrate X-GLU is cleaved by the enzyme β-D-Glucosidase, which is characteristic of enterococci. This results in a color change of the broth to intensive blue-green.
Detection of coliforms in the food and beverages industry