Rapid detection of E. coli from water and food samples by fluorogenic detection methods.
Lauryl Sulfate Broth was formulated by Mallmann and Darby for detection of coliform bacteria in water. This is a selective medium because it contains sodium lauryl sulfate which inhibits Gram positive microorganisms. Lactose is added to detect rapid lactose fermentation by coliforms. The addition of 4- methylumbelliferyl-B-D-glucuronide (MUG) to Lauryl Sulfate Broth allows for the rapid detection (4-24 hours) of E. coli-When the incubated medium is observed for fluorescence using a long-wave UV light (365 nm) source. It can also detect anaerogenic E-coli strains. Most strains of E. coli produce B- glucuronidase which hydrolyzes MUG to the fluorogenic compound 4- methyl-umbelliferone. Studies by Feng and Hartman noted that most E coli strains (96%) and all enterotoxigenic E coli strains (100%) and a moderate number of Salmonella (17%) and Shigella (40%) stains produce B-glucuronidase. False positives can also be caused by Streptococcus sp.
Quality Control Summary:
Expected cultural response after 18-24 hours at 35.0 degrees C.
Organism Result
Escherichia coli ATCC 25922 Growth, Gas +, Fluorescence +
Proteus mirabilis ATCC 12453 Growth, Gas -, Fluorescence -
Staphylococcus aureus ATCC 25923 No Growth
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