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Material Safety Data Sheet

Organisms

Organisms this product works with:

Dehydrated Culture Media

EC BROTH

Code: CM0853

A selective broth for the growth of coliforms and Escherichia coli from food and environmental samples.

Typical Formula*

gm/litre

Tryptone

20

Lactose

5.0

Bile salts No. 3

1.5

Di-potassium phosphate

4.0

Mono-potassium phosphate

1.5

Sodium chloride

5.0

pH 6.9 ± 0.2 @ 25°C

 
* Adjusted as required to meet performance standards

Directions
Dissolve 37g in 1 litre of distilled water. Dispense into final containers and sterilize by autoclaving at 121°C for 15 minutes.

Description
The original formulation described by Perry and Hajna1 with Tryptose as the nitrogen source was subsequently substituted for Tryptone . The medium has been shown to be a reliable medium producing dependable results in 24 to 48 hours2.

EC Broth is a selective medium for the differentiation of faecal coliforms and the confirmatory test for Escherichia coli from food and environmental samples3,4. It is also suitable for the enumeration of presumptive E. coli in milk and milk products using the most probable number technique2.

Escherichia coli is a common Gram-negative micro-organism which may be present in food and water samples. The presence of E. coli cells may be indicative of faecal contamination, although their ingestion does not necessarily have adverse effects on health. Nevertheless, certain strains are responsible for diarrhoeal disease and can also lead to more serious forms of illness.

The presence of E. coli in water is also regarded as a specific indicator of faecal pollution, but lack of rapid identification methods means that the non-specific group - faecal coliforms - is also used as the indicator of such pollution. In this regard, it is important to differentiate between coliforms of faecal origin and those from other sources.

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

Examination of shellfish5

44.5°C

Milk and milk products3

44.0°C

Water and wastewater4

44.5°C

Other foodstuffs5

45.5°C

The Quality Control of EC Broth CM0853 includes testing in accordance with ISO 11133:20146.

Technique
The formulation includes a buffered lactose broth and bile salts No.3. The presence of bile salts inhibits the growth of spore formers and enterococci, but allows the growth of E.coli and coliforms. Gas production from lactose fermentation is indicated by using inverted Durham tubes. Methods are summarised below but refer to the appropriate standard for the detailed technique.

1. Milk and Milk Products/Presumptive E. coli3 (ISO)
Tubes containing inverted Durham tubes with single and double strength Lauryl Tryptose Broth (CM0451) are inoculated with samples as described in the standard method. Incubate at 37°C for 24-48 hours and examine for gas production. Inoculate tubes showing gas production into a new series of tubes containing 10ml of EC Broth (CM0853) containing inverted Durham tubes, and incubate at 44°C for 24-48 hours. Transfer an inoculum from tubes giving rise to gas formation to tubes containing Tryptone Water (CM0087), and incubate for 24-48 hours at 44°C. Examine for indole production and calculate the Most Probable Number (MPN) of presumptive E. coli. For full details please refer to the ISO Standard Method.

2. Faecal Coliform Test4 (APHA)
For differentiation of faecal coliforms inoculate EC Broth (CM0853) fermentation tubes containing inverted Durham tubes, and incubate in a water bath at 44.5°C for 24 ± 2°C hours. Gas production and growth within 24 hours or less is considered a positive faecal coliform reaction. For full details please refer to the APHA Standard Method3.

3. Confirmatory Test for E. coli5 (FDA/BAM)
From each gassing Lauryl Tryptose Broth (CM0451) tube, transfer a loopful of suspension to EC Broth (CM0853) tubes containing inverted Durham tubes. Incubate at 45.5°C, and examine for gas production after 24 and 48 hours. Gassing tubes are streaked onto EMB Agar (CM0069) and incubated at 35°C for 18-24 hours. Transfer 2 suspicious colonies from each plate onto PCA (CM0325), incubate for 18-24 hours at 35°C and confirm with morphological and biochemical tests. For full details please refer to the FDA/BAM Standard Method4.

Storage conditions and Shelf Life
Store the dehydrated medium at 10-30°C and use before the expiry date on the label.
Store the prepared medium at 2-8°C for up to 4 weeks.

Appearance
Dehydrated medium: White, free-flowing powder
Prepared medium: Straw coloured solution

Quality control

(Incubation is at 37°C and 44°C for 24 to 48 hours)

Positive control:

Expected results

Escherichia coli ATCC® 25922 *
WDCM00013

Turbid growth; gas production

Negative controls:

 
Pseudomonas aeruginosa ATCC®27853*
WDCM00025
No growth
* This organism is available as a Culti-Loop®

References
1. Hajna, A. A. and Perry, C. A. (1943) Amer. J. Pub. Hlth. 33, 550-556.
2. Perry, C. A. and Hajna, A. A. (1944) Amer. J. Pub. Hlth. 34, 735-738.
3.International Organisation for Standardisation: Milk and Milk Products - Enumeration of presumptive Escherichia coli. Part 1. Most probable number technique ISO 11866-1 : 1997.
4. American Public Health Association (1998) Standard Methods for the Examination of Water and Wastewater. 20th Edn. APHA Inc. Washington DC.
5."Association of Official Analytical Chemists" F.D.A. Bacteriological Analytical Manual 8th Edition (1995) AOAC, Arlington Va.
6. International Organization for Standardization. ISO 11133:2014 Microbiology of food, animal feed and water - Preparation, production, storage and performance testing of culture media

 
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