Brain Heart Infusion Broth ISO

Calf brain infusion, enzymatic digest of animal tissue and beef heart infusion provide nitrogen, vitamins, minerals and amino acids essential for growth. Sodium chloride supplies essential electrolytes for transport and osmotic balance. Sodium hydrogen phosphate is a buffer. Glucose is the fermentable carbohydrate providing carbon and energy.

The coagulase test is considered positive if the clot volume is more than half of the original liquid volume.

Preparation

Suspend 37 grams of the medium in one liter of distilled water. Mix well and dissolve by heating with frequent agitation. Boil for one minute until complete dissolution. Dispense into appropriate containers and sterilize in autoclave at 121 °C for 15 minutes.

According to ISO 6888

For the confirmation of coagulase-positive staphylococci according to ISO 6888:

1. Collect the inoculum from the surface of each selected colony using a sterile wire and introduce the inoculum into a tube or bottle that contains the Brain-heart infusion.
2. Incubate at 35-37 °C for 24 ± 2 hours.
3. Under aseptic conditions, add 0.1 mL of each culture to 0.3 mL of rabbit plasma in sterile hemolysis tubes or bottles.
4. Incubate at 35-37 °C.
5. Examine the coagulase plasma by inclining the tube after incubating for 4 to 6 hours.

If the test is negative:

1. Re-examine after 24 hours of incubation or after the incubation period recommended by the manufacturer is over.
2. As a negative control for each plasma lot, add 0.1 mL of Brain-heart infusion to the quantity of rabbit plasma indicated by the manufacturer and incubate without inoculation.
3. For the test to be valid, the plasma control should not show any signs of coagulation.

• International Standard ISO 6888-1 Microbiology of food and animal feeding stuffs - Horizontal method for the enumeration of coagulase-positive staphylococci (Staphylococcus aureus and other species) - Part 1: Technique using Baird-Parker agar medium.