Composition

*  Dehydrated powder, hygroscopic in nature, store in a dry place, in tightly-sealed containers below 25°C and protect from direct Sunlight.

Instructions for Use

Dissolve 37gms in 1000ml distilled water. Gently heat to boiling with gentle swirling and dissolve the medium completely. Dispense in test tubes containing inverted Durham tubes. Sterilize by autoclaving at 15 psi (121°C) for 15 minutes. Cool the medium as quickly as possible for use.

Appearance: Yellow colour, clear solution

pH (at 25°C): 6.9 ± 0.2

Principle

EC BROTH is used for the selective enumeration of faecal and non-faecal coliforms in water. Medium contains Casein enzymatic hydrolysate, provides amino acids and nitrogen for the growth. Bile salt mixture inhibit gram-positive bacteria especially bacilli and faecal Streptococci sp. Sodium chloride maintains the osmotic balance of the medium. Monopotassium phosphate and Dipotassium phosphate are the buffering agents and helps to control the pH during fermentation of lactose. Lactose- positive bacteria metabolize Lactose and produces gas, (as indicated by Durham tubes) within 24 hour or less is a presumptive evidence of the presence of coliform bacteria or indicating fecal coliforms. Inoculate the tubes containing 10 ml of EC Broth and the Durham tubes and incubate at wished temperature for 24 – 48 hours. In case of gas formation the Durham tubes rises up. This medium can be used at 37°C for the detection of coliforms (no gas formation of E. coli) or use at 45-50°C for the isolation of Escherichia coli and other coliforms (gas formation of E. coli).

The identification criteria for E. coli and faecal coliforms is the fermentation of lactose to acid and gas within 24-48 hours at 44 – 45.5°C, dependent upon which method and/or material is used, for eg.,

Milk and milk products: 44.00C Water and wastewater: 44.50C Other material or foodstuffs: 45.50C Interpretation

Cultural characteristics observed after inoculating (103CFU/ml), on incubation at 44.5°C for 24 – 48 hours.

+++ = positive reaction

–       = negative reaction

References

1. American Public Health Association, American Water Works Association and Water Pollution Control Federation: Standard Methods for Examination of Water and Wasterwater, 20th ed., Washington. (1998).
2. L.J. Harris, M.E. Stiles, E. coli counts in vacuum-packed beef by the MPN technique, J. Food Prot. 55, 266. (1992).
3. Fishbein and Surkiewicz, Appl. Microbiol., 12:127. (1964).
4. Tennant et al., Can. J. Microbiol., 1:733. (1961).
5. Hajna and Perry, Am. 1 Publ. Health, 33:550. (1943).