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Material Safety Data Sheet

Organisms

Organisms this product works with:

Dehydrated Culture Media

COOKED MEAT MEDIUM

Code: CM0081

an excellent medium for the primary growth and maintenance of aerobic and anaerobic organisms

Typical Formula*

gm/litre

Heart muscle

454.0

Peptone

10.0

`Lab-Lemco’ powder

10.0

Sodium chloride

5.0

Glucose

2.0

pH 7.2 ± 0.2 @ 25°C

 
* Adjusted as required to meet performance standards

Directions
Suspend 10g in 100ml of distilled water (or 1g amounts in 10ml volumes of water in tubes). Allow to stand for 15 minutes until the meat particles are thoroughly wetted. Sterilise by autoclaving at 121°C for 15 minutes. Do not cool the bottles rapidly because ebullition will expel the meat particles from the containers.

Description
Cooked Meat Medium prepared from heart tissue is a well established medium for the cultivation of anaerobic and aerobic organisms1.

It has the ability to initiate bacterial growth from very small inocula and to maintain the viability of cultures over long periods of time. Mixed cultures of bacteria survive in Cooked Meat Medium without displacing the slower growing organisms. The products of growth do not rapidly destroy the inoculated organisms and therefore it is an excellent medium for the storage of aerobic and anaerobic bacteria.

The addition of glucose to the formulation allows rapid, heavy growth of anaerobic bacteria in a short time and leads to a more rapid identification of important anaerobes. The improved growth also enhances GLC identification of anaerobic bacteria.

The improved clarity of the supernatant broth permits earlier detection of growth especially when combined with the increased growth of most organisms. Slower growing isolates will yield detectable growth within 45 hours incubation.

Technique
Anaerobic Culture
It is preferable to use freshly reconstituted and sterile medium which is inoculated as soon as it has cooled to approximately 35°C. Tubes which are not used on the day of preparation should be placed in a boiling water bath or steamer for about 15 minutes to remove dissolved oxygen. They should be allowed to cool without agitation and then inoculated.

Inoculation should be made near the bottom of the tube in the meat particles.

Clostridia may be divided into two main groups by their action on the medium.
(i) Saccharolytic Organisms
There is rapid production of acid and gas but no digestion of the meat. Cultures may have a slightly sour smell, with reddened protein.
(ii) Proteolytic Organisms
Proteolysis causes decomposition of the meat with the formation of foul-smelling sulphur compounds and blackening. However, some saccharolytic strains also produce Hydrogen sulphide which will cause blackening but to a lesser degree.
Aerobic Culture
The tube of medium is incubated with the cap loose and no seal is required. Aerobes grow at the top whilst more anaerobic species grow deeper in the medium.

Incubation
Aerobic organisms

Incubate for up to 7 days at 35°C with loosened caps. Examine daily for turbidity, gas or changes in the meat particles.
Anaerobic organisms
Use freshly reduced medium and incubate for up to 21 days at 35°C. Examine daily for changes in the medium. Make films and subculture at intervals.
Maintenance of stock cultures
Hold at room temperature after the initial incubation at 35°C. Subculture every 4-6 months.

Storage conditions and Shelf life
Store the dehydrated medium at 10-30°C and use before the expiry date on the label.
Store the prepared medium at room temperature, in the dark with tightened caps for up to 6 months.

Appearance
Dehydrated medium: Brown granules
Prepared medium: Dark straw with brown granules

Quality control

Positive controls:Expected results
Clostridium histolyticum ATCC® 19401Turbid growth; proteolysis
Clostridium perfringens ATCC® 13124Turbid growth; saccharolysis, proteolysis
Negative control: 
Uninoculated mediumNo change
* This organism is available as a Culti-loop®

Precautions
The excellent recovery properties of Cooked Meat Medium mean that mixed cultures commonly result from sample inoculation.
Blackening of the medium will not take place if the pH is acid.
Carbohydrate fermentation may inhibit proteolysis.

Reference
1. Robertson M. (1916) J. Path. Bact. 20. 327-349.

 
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