HiCrome™ ECD Agar w/ MUG

Intended use

Recommended for the detection of Escherichia coli in water and food samples by using a combination of chromogenic and fluorogenic substrate.

Composition**

Final pH ( at 25°C) 7.0±0.2

**Formula adjusted, standardized to suit performance parameters

Directions

Suspend 53.17 gram in 1000 ml purified/distilled water. Heat to boiling to dissolve the medium completely. Sterilize by autoclaving at 15 lbs pressure (121°C) for 15 minutes. Cool to 45-50°C. Mix well and pour into sterile Petri plates.

Principle And Interpretation

HiCrome™ ECD Agar w/ MUG is recommended for rapid detection of Escherichia coli by using a combination of chromogenic and fluorogenic substrates. The presence of Escherichia coli is indicated by blue coloured colony formation due to cleavage of chromogenic substrate. Fluorogenic substrate permits rapid detection of Escherichia coli when medium is observed for fluorescence using UV light (1,2). Fluorogenic substrate also detects anaerogenic strains, which may not be detected in conventional procedure (1). It is hydrolysed by enzyme ß-D-glucuronidase, possessed by Escherichia coli to yield a fluorescent end product. The reaction is indicated by a blue fluorescence under UV light. Tryptone provides carbon, nitrogen substances, long chain amino acids, vitamins and other essential nutrients. Lactose is the fermentable carbohydrate. Sodium chloride maintains osmotic equilibrium. The medium has a strong buffering system to control the pH in the presence of fermentative action. The bile salt mixture inhibits gram-positive bacteria especially Bacillus species and faecal Streptococci.

Type of specimen

Food samples; Water samples.

Specimen Collection and Handling:

For food samples, follow appropriate techniques for sample collection and processing as per guidelines (3). For water samples, follow appropriate techniques for sample collection, processing as per guidelines and local standards (4). After use, contaminated materials must be sterilized by autoclaving before discarding.

Warning and Precautions :

Read the label before opening the container. Wear protective gloves/protective clothing/eye protection/ face protection. Follow good microbiological lab practices while handling specimens and culture. Standard precautions as per established guidelines should be followed while handling specimens. Safety guidelines may be referred in individual safety data sheets.

Limitations

1. ß-glucuronidase is present in 97% of E.coli strains, however few E.coli may be negative.
2. Slight colour variation may be observed depending upon the utilization of the substrate by the organism.
3. Further biochemical and serological test needs to be carried out for confirmation.

Performance and Evaluation

Performance of the medium is expected when used as per the direction on the label within the expiry period when stored at recommended temperature.

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 gel forms in Petri plates

Reaction Reaction of 5.32% 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 44-45°C for 18-24 hours.

Key : (*) Corresponding WDCM numbers.

Storage and Shelf Life

Store between 15-25°C in a tightly closed container and the prepared medium at 2-8°C. Use before expiry date on the label. On opening, product should be properly stored dry, after tightly capping the bottle in order to prevent lump formation due to the hygroscopic nature of the product. Improper storage of the product may lead to lump formation. Store in dry ventilated area protected from extremes of temperature and sources of ignition Seal the container tightly after use. Product performance is best if used within stated expiry period.

Disposal

User must ensure safe disposal by autoclaving and/or incineration of used or unusable preparations of this product. Follow established laboratory procedures in disposing of infectious materials and material that comes into contact with sample must be decontaminated and disposed of in accordance with current laboratory techniques (5,6).

Reference

1. Feng PCS and Hartman PAS, (1982), Appl. Environ. Microbiol. 43:132.
2. Lipps WC, Braun-Howland EB, Baxter TE,eds. Standard methods for the Examination of Water and Wastewater, 24th ed. Washington DC:APHA Press; 2023.
3. Robinson (1984), Appl. Environ. Microbiol., 48:285.
4. Salfinger Y., and Tortorello M.L. , 2015, Compendium of Methods for the Microbiological Examination of Foods, 5th Ed.,American Public Health Association, Washington, D.C.
5. Isenberg, H.D. Clinical Microbiology Procedures Handbook. 2nd Edition.
6. Jorgensen, J.H., Pfaller, M.A., Carroll, K.C., Funke, G., Landry, M.L., Richter, S.S and Warnock., D.W. (2015) Manual of Clinical Microbiology, 11th Edition. Vol. 1.