NEET MDS

The Power Course

Robertson's Cooked Meat (RCM) media, contains meat of:



Choices

1 ) Beef Heart
2 ) Ox brain
3 ) Sheep brain
4 ) Ox liver

Explanation


Robertson's cooked meat media:

It was originally developed by Robertson in 1916 for the cultivation of anaerobes isolated from wounds. It is a liquid enrichment media also known as Cooked Meat Broth (CMB).  This media contains pieces of fat-free minced cooked meat of ox/beef heart and nutrient broth. It is mainly used for the cultivation of microaerophilic, and anaerobic microorganisms, especially Clostridium species. It helps to differentiate between putrefactive and saccharolytic species.

Procedure to use Robertson's cooked meat media:

Prior to inoculation, this medium is boiled to make it oxygen-free. Followed, inoculation to be done and cover it with a layer of sterile liquid paraffin oil. This paraffin cover prevents the entry of oxygen in the medium thus aiding to create an anaerobic or reduced environment. 

Significance of ingredients:

1. Unsaturated fatty acids: These are from the cooked meat.  They utilize oxygen for auto-oxidation. This reaction is catalyzed by haematin in the meat.

2. Glutathione and cysteine: These two are the reducing agents present in meat which utilize oxygen and create an anaerobic environment. 

3. Sulphydryl compounds: They contribute to reduced oxidation-reduction potential. This is produced more by cooking the meat. 

Interpretation of culture: 

Two types of interpretations can be made based on saccharolytic or proteolytic reactions.

1. Saccharolytic reaction: Indicated by reddening of the meat with a rancid smell due to carbohydrate decomposition.

2. Proteolytic reaction: This is shown by the blacking of the meat with a very unpleasant smells due to protein decomposition

Eg:

1. Clostridium perfringens: Saccharolytic anaerobes (turn the color of meat pieces into red)

2. Clostridium tetani: Proteolytic anaerobes (blacking of the meat)

Uses of Robertson’s Cooked Meat medium: 

1. Used for cultivation of aerobic, microaerophilic, and anaerobic microorganisms, especially Clostridium species.

2. It helps in the growth of both spore-forming and non-spore forming obligate anaerobes.

3. RCM is useful for cultivating organisms from a very small inoculum.

4. This Cooked Meat Medium also preserves the viability of organisms over a long period of time which is useful in maintaining anaerobic stock organisms.

5. The Food and Drug Administration (FDA) recommends the use of this media in the identification of Clostridium perfringens from food.


Answer

Beef Heart

Last Modified : 25-Dec-2019

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