EC Broth (E. coli Broth)

EC Broth (E. coli Broth)
Selective Enrichment Medium for Escherichia coli and Fecal Coliforms

Catalog Number: AS-1214

Overview
EC Broth (also known as E. coli Broth) is a selective enrichment liquid medium originally developed by Hajna and Perry (1951) for the detection, isolation, and enumeration of fecal coliforms, particularly Escherichia coli, in water, milk, food, and environmental samples.

The medium incorporates bile salts to inhibit Gram-positive bacteria and non-intestinal coliforms, while lactose serves as a fermentable carbohydrate to promote gas production in Durham tubes. A buffered phosphate system maintains stable pH and supports recovery of stressed or low-count organisms. Incubation at elevated temperature (44.5 °C) provides enhanced specificity for E. coli confirmation. EC Broth is widely used in the Most Probable Number (MPN) technique and complies with APHA, FDA-BAM, ISO 7251, and NF ISO 16649 standards.

Applications
• Selective enrichment and detection of fecal coliforms and E. coli in drinking, wastewater, and recreational water
• Enumeration of coliforms in milk, dairy products, and shellfish using MPN methods
• Isolation from food samples such as meat and vegetables for hygiene monitoring
• Confirmation of thermotolerant E. coli prior to subculture on EMB or MacConkey agar

Key Features & Benefits
• Bile salts selectively inhibit Gram-positive bacteria while allowing high recovery of E. coli
• Lactose fermentation produces gas in Durham tubes for rapid presumptive identification
• Elevated incubation at 44.5 °C enhances specificity for E. coli
• Buffered formulation supports injured cells from chlorinated or stressed environments
• Clear, light straw-coloured broth enables easy turbidity and gas observation
• Suitable for incubation at 37 °C (coliforms) or 44.5 °C (E. coli confirmation)

Principle of the Medium
EC Broth selectively enriches fecal coliforms through bile salt inhibition of competing flora. Lactose fermentation by coliforms results in acid and gas production, detected using Durham tubes. The phosphate buffer system stabilises pH during incubation, while elevated temperature incubation (44.5 °C) suppresses non-thermotolerant organisms, enabling presumptive confirmation of E. coli.

Typical Composition (per litre)
Tryptone (or Pancreatic Digest of Casein) – 20.0 g
Lactose – 5.0 g
Bile Salts No. 3 – 1.12 g
Sodium Chloride – 5.0 g
Dipotassium Phosphate – 4.0 g
Potassium Dihydrogen Phosphate – 1.5 g

Final pH: 6.9 ± 0.2 at 25 °C

Preparation
Suspend 36.62 g of dehydrated medium in 1 L of purified or distilled water.
Mix thoroughly until dissolved; gentle heating may be used, but avoid boiling.
Dispense into tubes containing inverted Durham tubes (e.g., 10 mL per tube).
Sterilise by autoclaving at 121 °C (15 psi) for 15 minutes with caps loosened.
Cool to room temperature and tighten caps.
The prepared broth should be clear and light straw-coloured without precipitate.

Incubation & Interpretation
Inoculate aseptically with homogenised sample dilutions.
Incubate aerobically:
• 37 °C for 24 ± 2 hours for coliform detection
• 44.5 ± 0.2 °C (water bath, water level above broth) for E. coli confirmation

Positive reaction: turbidity with gas in Durham tube
Negative reaction: clear broth with no gas

Presumptive positives should be confirmed by biochemical testing (e.g., IMViC).

Storage & Stability
Dehydrated medium: Store at 10–30 °C in a tightly closed container, protected from moisture and light
Prepared broth: Store at 2–8 °C in sealed tubes and use within 2 weeks
Discard if turbid without inoculation, contaminated, or discoloured

Intended Use
For laboratory research and microbiological quality control use only.
Not for human or veterinary consumption.
Handle using appropriate biosafety precautions (BSL-2).

Quality & Compliance
Manufactured under controlled conditions for batch-to-batch consistency.
Compliant with APHA, FDA-BAM, ISO 7251, and NF ISO 16649 methodologies.
Performance comparable to leading international reference media suppliers.

Customs & Trade Information
HS / AHECC Code: 3821.00.00
Prepared culture media for the development or maintenance of microorganisms