MUG Bromocresol Purple Broth w/ Lactose

MUG Bromocresol Purple Broth w/ Lactose is used for identification of Escherichia coli and coliform bacteria from water samples by a fluorogenic assay method.

Composition**

Final pH ( at 25°C): 7.0±0.2

**Formula adjusted, standardized to suit performance parameters

Directions

Suspend 36.03 grams or if desired, suspend 72.06 grams in 1000 ml distilled water to prepare double strength medium. Heat if necessary to dissolve the medium completely. Dispense into test tubes containing inverted Durhams tubes. Sterilize by autoclaving at 115°C for 20 minutes.

Principle And Interpretation

Escherichia coli is a member of the faecal coliform group of bacteria. Detection of E. coli in water indicates faecal contamination. Enzymatic assay have been developed that allow the identification of this organism.

MUG-Bromocresol Purple Broth w/Lactose is used for identification of E. coli and coliform bacteria from water samples by a fluorogenic assay method (1).

In MUG-Bromocresol Purple Broth w/ Lactose, casein enzymic hydrolysate and papaic digest of soyabean meal provide carbon, nitrogen and other essential growth factors. Sodium chloride maintains the osmotic balance of the medium. The medium is supplemented with lactose as a carbon source. Bromocresol purple is a pH indicator which has yellow colour at acidic pH and purple colour at alkaline pH. Due to the fermentation of lactose, acid is produced which turns the medium yellow. Gas in the Durhams tubes after incubation indicates the presence of E. coli and/ or coliform bacteria. To confirm the detection, cover the culture with 5 mm layer of Kovacs indole reagent (R008). Development of a red ring after 1-2 minutes confirms presence of Escherichia coli.

All commensal E. coli produce ß-glucuronidase which cleave MUG to release 4-methylumbelliferone, a fluorescent compound. The fluorescence can be observed by exposure to long wave UV light (366 nm). The plates are exposed to ammonia fumes to increase fluorescence as suggested by Freir and Hartman (3).

Quality Control

Appearance Cream to yellow homogeneous free flowing powder

Colour and Clarity of prepared medium Purple coloured clear solution without any precipitate

Reaction Reaction of 3.6% w/v aqueous solution at 25°C. pH : 7.0±0.2

pH 6.80-7.20

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

Cultural Response

Storage and Shelf Life

Store below 30°C and the prepared medium at 2 - 8°C. Use before expiry date on the label.

Reference

1. Kolbeck K. et al, 1992, Zbl. Hyg., 193, 31437.
2. Maddocks J. L. and Greenan M. J. (1975) J. Clin. Pathol. 28. 686-687.
3. Freir T. A. and Hartman P. A. (1987) Appl. Env. Microbiol. 53. 1246-1250.