MUG Lauryl Sulphate Broth, Modified, 5 kg

The coliform group consists of several genera of bacteria belonging to the family Enterobacteriaceae . Lauryl Sulphate Broth formulated by Mallmann and Darby (1) is recommended by APHA for the detection and enumeration of coliform organisms in foods, water and waste water (2, 3). MUG is added in Lauryl Sulphate Broth as the fluorogenic compound which permits the rapid detection of Escherichia coli when observed under UV light where further confirmation is not required (2,4). MUG Lauryl Sulphate Broth, Modified is recommended by the ISO Committee (6) for enumeration of presumptive E.coli and other coliforms from milk and milk products. E.coli possesses the enzyme beta-glucuronidase and is capable of cleaving the fluorogenic substrate 4-Methylumbelliferyl beta-D-glucuronide (MUG) with the corresponding release of the fluorogen. MUG detects anaerogenic strains, which may not be detected in the conventional procedure. Feng and Hartman (5) used MUGcontaining medium for studying beta-glucuronidase activity and found that E.coli has 96-100% activity, while Salmonella species has 17% and Shigella species 40% activity and other genera were negative. For weakly positive strains, incubation should be carried out overnight. Robison (4) achieved no false negative results and about 5% false positive results. Casein enzymic hydrolysate provides nutrients while lactose acts as energy source. Sodium lauryl sulphate inhibits many organisms other than coliforms. 4-methylumbelliferyl- beta -D-glucuronide is hydrolyzed by the enzyme beta-glucuronidase to yield 4-methylumbelliferone, a fluorescent end product. Inoculate 10 ml of the test specimen into three tubes each of single strength and double strength . Incubate the tubes at 35°C for 24 hours. Observe for opacity and gas formation. For confirmation of presumptive E.coli , observe for fluorescence and perform indole reaction using Kovacs Reagent (R008) (6). Storage and Shelf-life: Store below 30°C in tightly closed container and the prepared medium at 2 8°C. Use before expiry date on the label. References: 1. Mallmann W. L. and Darby C. W., 1941, Am. J. Public Health, 31:127. 2. Downes F. P and Ito K., (Eds.), 2001, Compendium of Methods for the Microbiological Examination of Foods, 4th Ed., APHA, Washington, D.C. 3. Greenberg A. E., Trussell R. R. and Clesceri L. S., (Eds.), 1985, Standard Methods for the Examination of Water and Wastewater, 16th Ed., APHA, Washington, D.C. 4. Robison, 1984, Appl. Environ. Microbiol., 48:285. 5. Feng P. C. S. and Hartman P. A., 1982, Appl. Environ. Microbiol., 43 : 1320.6. International Organization for Standardization (ISO), ISO 11866-2:1997 (E)