Dehydrated Culture Medium
Enriched medium for the cultivation and maintenance of anaerobic bacteria, especially Clostridium species
Cat. No. AS-118312.5 g / 100 mLpH 7.2 ± 0.2Enriched mediumAnaerobe maintenance
At a glance
- Target organismsAnaerobes, Clostridium
- Incubation35–37 °C
- Time24–48 h
- Sterilisation121 °C, 15 min
Manufactured in Melbourne. TDS and SDS available. Batch COA on request.
Overview
Cooked Meat Medium, also known as Robertson's Cooked Meat Medium, is an enriched medium for the cultivation and maintenance of anaerobic bacteria, especially Clostridium species. It also supports many aerobic and facultative organisms.
The medium is supplied as dehydrated granules. Once rehydrated and sterilised, the heart-tissue particles settle at the bottom of the tube under a nutrient broth. Reducing substances in the meat lower the oxidation-reduction potential, so anaerobes can grow in the lower part of the tube.
Key features
- Built-in reducing conditions from sulfhydryl compounds in heart tissue
- Visible reactions: meat digestion and blackening show proteolytic activity
- A classic medium for keeping anaerobic stock cultures
Principle of the Medium
| Component | Function |
|---|---|
| Beef heart solids | Nutrients, plus reducing substances (sulfhydryl groups) that lower the oxidation-reduction potential |
| Proteose peptone | Nitrogen, amino acids and peptides |
| Dextrose | Fermentable carbohydrate and energy source |
| Sodium chloride | Maintains osmotic balance |
Inoculate near the bottom of the tube, among the meat particles. Anaerobes grow in the lower, reduced zone; aerobes grow near the surface.
Typical Composition
| Ingredient | g/L |
|---|---|
| Beef heart solids (equivalent to 454 g beef heart) | 98.00 |
| Proteose peptone | 20.00 |
| Dextrose (glucose) | 2.00 |
| Sodium chloride | 5.00 |
| Total | 125.00 |
Final pH 7.2 ± 0.2 at 25 °C. Formula may be adjusted and/or supplemented to meet performance specifications.
Reading the Results
| Observation | Indicates |
|---|---|
| Turbidity and/or gas bubbles | Growth |
| Meat particles turn pink or red, gas, sour odour | Saccharolytic activity (for example C. perfringens) |
| Meat particles blacken and break down, foul odour | Proteolytic activity (for example C. sporogenes) |
Applications
| Field | Typical use |
|---|---|
| Food microbiology | Enrichment and cultivation of Clostridium species, including C. perfringens |
| Culture collections and research | Maintenance and storage of anaerobic stock cultures |
| Spore studies | Recovery of spore-forming anaerobes after heat treatment |
| Teaching laboratories | Demonstrating saccharolytic and proteolytic clostridia |
Comparable Products
| Manufacturer | Product | Relationship |
|---|---|---|
| HiMedia Laboratories | M149 Cooked Medium (R.C. Medium) | Comparable published formulation |
| US FDA BAM | Media M42 Cooked Meat Medium | Comparable published formulation |
Frequently Asked Questions
Why do I need to boil the medium before use?
Stored medium absorbs oxygen. Boiling or steaming for a few minutes, then cooling without shaking, removes dissolved oxygen and restores the reducing conditions anaerobes need.
How do I tell saccharolytic from proteolytic clostridia?
Saccharolytic species such as C. perfringens turn the meat pink or red with gas and a sour odour. Proteolytic species such as C. sporogenes blacken and break down the meat with a foul odour.
How much do I use per tube?
1.25 g per 10 mL tube (125 g/L). A 500 g pack makes about 400 tubes.
Will aerobes grow in it?
Yes. The medium is non-selective, so aerobic and facultative organisms grow near the surface.
Intended use: For laboratory microbiological testing, quality control and research use only. Not intended for direct use in food, human or veterinary therapeutic applications, diagnosis, or consumption.
Mode of Action
Beef heart solids supply nutrients and sulfhydryl-containing reducing substances that lower the oxidation-reduction potential, allowing anaerobes to grow among the meat particles. Proteose peptone and dextrose provide nitrogen and energy, and sodium chloride maintains osmotic balance.
Preparation
- Suspend 12.5 g of granules in 100 mL of cold purified or distilled water, or add 1.25 g to each tube with 10 mL of water.
- Mix and allow to stand for 15 minutes so all particles are wetted.
- Dispense into tubes or flasks, keeping the particles evenly distributed.
- Sterilise by autoclaving at 121 °C for 15 minutes.
- Use on the day of preparation. Otherwise, boil or steam for a few minutes and cool without agitation before inoculation, to remove dissolved oxygen.
Incubation and Interpretation
| Parameter | Condition |
|---|---|
| Inoculation | Close to the bottom of the tube, among the meat particles |
| Temperature | 35–37 °C |
| Time | 24–48 hours (slow-growing isolates may need longer) |
| Spore test | Heat one inoculated tube at 80 °C for 10 minutes, then incubate as above |
Reactions in the meat are presumptive. Confirm identity with further biochemical, serological or molecular tests.
Limitations
- Non-selective: aerobes and facultative organisms will also grow.
- Stored medium must be boiled or steamed and cooled before use to restore reducing conditions.
- Toxigenic Clostridium species must be handled under appropriate biosafety containment and any applicable regulations.
Literature and References
- Robertson M. Notes upon certain anaerobes isolated from wounds. J Pathol Bacteriol. 1916;20:327–349.
- US Food and Drug Administration. Bacteriological Analytical Manual, Media M42: Cooked Meat Medium.
- MacFaddin JF. Media for Isolation–Cultivation–Identification–Maintenance of Medical Bacteria, Vol. I. Williams & Wilkins; 1985.
- Atlas RM. Handbook of Microbiological Media, 4th ed. CRC Press; 2010.
- Salfinger Y, Tortorello ML (eds). Compendium of Methods for the Microbiological Examination of Foods, 5th ed. APHA; 2015.
Hazard Identification
Not classified as hazardous according to the GHS (Rev. 7) as adopted in Australia under the model WHS Regulations. Not Dangerous Goods under the ADG Code.
Dust may cause mild mechanical irritation of the eyes and respiratory tract. Contains material of bovine origin.
Composition
| Ingredient | CAS No. | % w/w |
|---|---|---|
| Beef heart solids | Not available | 78.4 |
| Proteose peptone | 73049-73-7 | 16.0 |
| D-Glucose (dextrose) | 50-99-7 | 1.6 |
| Sodium chloride | 7647-14-5 | 4.0 |
First Aid
| Route | Action |
|---|---|
| Inhalation | Move to fresh air. Seek medical advice if symptoms persist. |
| Skin | Wash with soap and water. |
| Eyes | Rinse with water for several minutes. Seek medical advice if irritation persists. |
| Ingestion | Rinse mouth. Do not induce vomiting. Seek medical advice if unwell. |
Poisons Information Centre (Australia, 24 h): 13 11 26
Handling, Spills and Disposal
- Avoid generating and breathing dust.
- Spills: sweep up or HEPA-vacuum without raising dust; wash the area with water.
- Unused product: dispose of as non-hazardous waste under local regulations.
- Inoculated medium: treat as biohazardous and decontaminate (for example by autoclaving) before disposal.
Quality Control Specification
Each batch is tested for growth performance. Incubation at 35–37 °C for 40–48 hours.
| QC organism | Strain | Inoculum (CFU) | Expected result |
|---|---|---|---|
| Clostridium perfringens | ATCC 12924 | 50–100 (≤ 100) | Luxuriant growth |
| Clostridium sporogenes | ATCC 11437 | 50–100 (≤ 100) | Luxuriant growth |
| Enterococcus faecalis | ATCC 29212 | 50–100 (≤ 100) | Luxuriant growth |
Physical and Chemical Tests
| Test | Specification |
|---|---|
| Appearance, powder | Brown granules |
| Appearance, prepared medium | Amber, clear to slightly opalescent broth over insoluble particles |
| pH, prepared medium (25 °C) | 7.00–7.40 |
The information on this page is provided in good faith as a guide to the properties and use of this product and does not constitute a warranty of fitness for a particular purpose. Users are responsible for confirming suitability for their application. Ausamics Pty Ltd · ABN 56 676 640 467 · 36/25 Trafalgar Road, Epping VIC 3076, Australia · support@ausamics.com