MUG Nutrient Agar

MUG Nutrient Agar is used for detection of Escherichia coli in water and food samples by a fluorogenic procedure.

Composition**

**Formula adjusted, standardized to suit performance parameters

Directions

Suspend 28.1 grams in 1000 ml distilled water. Heat to boiling to dissolve the medium completely. Sterilize by autoclaving at 15 lbs pressure (121°C) for 15 minutes. Mix well and pour into sterile Petri plates.

Principle And Interpretation

Escherichia coli is the member of faecal coliform group, presence of which in water indicates faecal contamination. These bacteria possess the enzyme b-glucuronidase and are capable of cleaving the fluorogenic substrate 4-Methylumbelliferyl beta-D-Glucuronide (MUG) with the release of the corresponding fluorogen, 4-Methylumbelliferone (1). Therefore incorporation of MUG and subsequent fluoroscense is confirmatory for presence of E. coli with no further confirmation required (2). MUG Nutrient Agar is recommended for detection of E. coli in water and food samples by a fluorogenic method. Presumptive E. coli in the samples can be directly inoculated into the medium.

Peptic digest of animal tissue, beef extract and yeast extract provide nitrogenous compounds and vitamin B complex. MUG is cleaved by the enzyme beta-glucuronidase of E.coli to release 4-methylumbelliferone which produces visible green-blue fluorescence under long wave UV light (1). Some strains of Salmonella and Shigella species also produce glucuronidase (3). Refer appropriate references for standard procedures (1).

Quality Control

Appearance Cream to yellow homogeneous free flowing powder

Gelling Firm, comparable with 1.5% Agar gel

Colour and Clarity of prepared medium Light amber coloured clear to slightly opalescent gel forms in Petri plates

Reaction Reaction of 2.81% w/v aqueous solution at 25°C. pH : 7.4±0.2

pH 7.20-7.60

Cultural Response

M1461: Cultural characteristics observed after an incubation at 35-37°C for 18-24 hours.

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.

Reference

1. Eaton A. D., Clesceri L. S. and Greenberg A. E. (ed.), 1995, Standard Methods for the Examination of Water and Wastewater, 19th Ed., American Public Health Association, Washington, D.C.
2. Feng J. S. and Hartman P. A., 1982, Appl. Environ. Microbiol., 43:1320
3. McFaddin J. F., 1985, Media for Isolation-Cultivation-Identification-Maintenance of Medical Bacteria. Vol. I, Williams and Wilkins, Baltimore.