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|
Technical Data |
| Nutrient Agar | M001 |
| Nutrient Agar is used for the cultivation of less fastidious microorganisms, can be enriched with blood or other biological fluids. |
| Composition** |
| Ingredients | Gms/Litre |
|---|---|
| Peptic digest of animal tissue | 5.000 |
| Sodium chloride | 5.000 |
| Beef extract | 1.500 |
| Yeast extract | 1.500 |
| Agar | 15.000 |
| Final pH ( at 25°C) | 7.4±0.2 |
| **Formula adjusted, standardized to suit performance parameters |
| Directions |
| Suspend 28 grams in 1000 ml distilled water. Heat to boiling to dissolve the medium completely. Dispense as desired and sterilize by autoclaving at 15 lbs pressure (121°C) for 15 minutes. Mix well before pouring. |
| Principle and Interpretation |
| Nutrient media are basic culture media used for maintaining microorganisms, cultivating fastidious organisms by enriching with serum or blood and are also used for purity checking prior to biochemical or serological testing (1, 2). Nutrient Agar is ideal for demonstration and teaching purposes where a more prolonged survival of cultures at ambient temperature is often required without risk of overgrowth that can occur with more nutritious substrate. This relatively simple formula has been retained and is still widely used in the microbiological examination of variety of materials and is also recommended by standard methods. It is one of the several non-selective media useful in routine cultivation of microorganisms (3, 4). It can be used for the cultivation and enumeration of bacteria which are not particularly fastidious. Addition of different biological fluids such as horse or sheep blood, serum, egg yolk etc. makes it suitable for the cultivation of related fastidious organisms. |
| Peptic digest of animal tissue, beef extract and yeast extract provide the necessary nitrogen compounds, carbon, vitamins and also some trace ingredients necessary for the growth of bacteria. Sodium chloride maintains the osmotic equilibrium of the medium. |
| Quality Control |
| Appearance |
| Cream to yellow homogeneous free flowing powder |
| Gelling |
| Firm, comparable with 1.5% Agar gel |
| Colour and Clarity |
| Light yellow coloured clear to slightly opalescent gel forms in Petri plates |
| Reaction |
| Reaction of 2.8% w/v aqueous solution at 25°C. pH : 7.4±0.2 |
| Cultural Response |
| M001: Cultural characteristics observed after an incubation at 35-37°C for 18-48 hours. |
| Organism | Inoculum (CFU) | Growth | Recovery | |||
| Escherichia coli ATCC 25922 | 50-100 | good-luxuriant | >=70% | |||
| Pseudomonas aeruginosa ATCC 27853 | 50-100 | good-luxuriant | >=70% | |||
| Salmonella Typhi ATCC 6539 | 50-100 | good-luxuriant | >=70% | |||
| Staphylococcus aureus ATCC 25923 | 50-100 | good-luxuriant | >=70% | |||
| Streptococcus pyogenes ATCC 19615 | 50-100 | good-luxuriant | >=70% |
| Reference |
| 1. Lapage S., Shelton J. and Mitchell T., 1970, Methods in Microbiology', Norris J. and Ribbons D., (Eds.), Vol. 3A, Academic Press, London. |
| 2. MacFaddin J. F., 2000, Biochemical Tests for Identification of Medical Bacteria, 3rd Ed., Lippincott, Williams and Wilkins, Baltimore. |
| 3. Downes F. P. and Ito K., (Ed.), 2001, Compendium of Methods for the Microbiological Examination of Foods, 4th Ed., American Public Health Association, Washington, D.C. |
| 4. American Public Health Association, Standard Methods for the Examination of Dairy |
| Products, 1978, 14th Ed., Washington D.C. |