HiMedia Laboratories GmbH, Marie-Curie-Str. 3, 64683, Einhausen, Germany.
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Intended Use
Recommended for isolation and identification of enteropathogenic Escherichia coli strains associated with infant diarrhoea.
Composition
| Ingredients | g/L |
|---|---|
| Peptone | 17.000 |
| Proteose peptone | 3.000 |
| D-Sorbitol | 10.000 |
| Bile salts mixture | 1.500 |
| Sodium chloride | 5.000 |
| Neutral red | 0.030 |
| Crystal violet | 0.001 |
| Agar | 13.500 |
| Final pH (at 25°C) | 7.1±0.2 |
**Formula adjusted, standardized to suit performance parameters.
Directions
Either streak, inoculate or surface spread the test inoculum (50-100 CFU) aseptically on the plate.
Principle And Interpretation
MacConkey Sorbitol Agar is based on the formulation described by Rappaport and Henigh (1). This medium is recommended for isolation of enteropathogenic Escherichia coli O157: H7, which ferments lactose but does not ferment sorbitol, hence produces colourless colonies. This organism has been recognized as a cause of hemorrhagic colitis (2). E.coli O157: H7 is a human pathogen associated with hemorrhagic colitis that results from the action of a shiga-like toxin (SLT) (3,4). On standard MacConkey Agar containing lactose, this strain is indistinguishable from other lactose- fermenting E.coli. In MacConkey Sorbitol Agar Base, lactose is replaced by sorbitol. Unlike most E.coli strains, E.coli O157:H7 ferments sorbitol slowly or not at all (5,6). The growth of E.coli O157:H7 on MacConkey Agar with Sorbitol shows colourless colonies and most of the fecal flora ferment sorbitol and appear pink. MacConkey Agar with Sorbitol therefore permits ready recognition of E.coli O157:H7 (3,4,7)
Peptone and proteose peptone supply necessary nutrients like nitrogenous and carbonaceous compounds, long chain amino acids, minerals, vitamins and trace ingredients for the growth of organisms. Crystal violet and bile salt mixture present in the medium inhibit growth of gram-positive bacteria. Sodium chloride maintains osmotic equilibrium. Neutral red is an indicator. D-Sorbitol is the fermentable carbohydrate.
Type of specimen
Clinical samples- stool, Food and Dairy samples.
Specimen Collection and Handling
For clinical samples follow appropriate techniques for handling specimens as per established guidelines (5,8).
For food and dairy samples, follow appropriate techniques for sample collection and processing as per guidelines (9,10,11). After use, contaminated materials must be sterilized by autoclaving before discarding.
Warning and Precautions
In Vitro diagnostic use. For professional use only. 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 clinical specimens. Safety guidelines may be referred in individual safety data sheets.
Limitations
- Individual organisms differ in their growth requirement and may show variable growth patterns on the medium.
- Each lot of the medium has been tested for the organisms specified on the COA. It is recommended to users to validate the medium for any specific microorganism other than mentioned in the COA based on the user's unique requirement.
- MacConkey Sorbitol Agar however should not be solely used to detect pathogenic E.coli O157: H7 strains as some non- toxic strains will also not ferment sorbitol (4).
- Further biochemical tests must be carried out for further 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
Sterile MacConkey Sorbitol Agar Plate in 90 mm disposable plates with smooth surface and absence of black particles/
cracks/bubbles
Colour of medium
Purplish red coloured medium
Quantity of medium
25 ml of medium in 90 mm disposable plates.
pH
6.90-7.30
Sterility Check
Passes release criteria
Cultural Response
Cultural characteristics observed after an incubation at 35-37°C for 18-24 hours.
| Organism | Inoculum (CFU) | Growth | Recovery | Colour of colony |
|---|---|---|---|---|
| Salmonella Typhi ATCC 6539 | 50-100 | luxuriant | >=50% | pink |
| Shigella flexneri ATCC 12022 (00126*) | 50-100 | luxuriant | >=50% | colourless |
| Escherichia coli ATCC 25922 (00013*) | 50-100 | luxuriant | >=50% | Pale pink-red |
| Escherichia coli serotype O11 and O55 | 50-100 | luxuriant | >=50% | Pale pink-red |
| Escherichia coli O157:H7 NCTC 29900 | 50-100 | luxuriant | >=50% | colourless |
Key: *Corresponding WDCM numbers.
Storage and Shelf Life
On receipt store between 20-30°C. Use before expiry date on the label. 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 clinical sample must be decontaminated and disposed of in accordance with current laboratory techniques (5,8).
| Product Name | MacConkey Sorbitol Agar Plate |
|---|---|
| SKU | MP298 |
| Customized Product Available | No |
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