Brain Heart Infusion Agar (B.H.I. Agar) 1048 Condalab

Brain Heart Infusion Agar (BHI Agar) is a solid medium rich in nutrients, suitable for the cultivation of several fastidious strains of bacteria, fungi, and yeasts. This medium can be used for the cultivation of a wide variety of fastidious microorganisms such as streptococci, meningococci, and pneumococci. The recommendation of BHI Agar is in Standard Methods for water testing and in antimicrobial susceptibility tests. The nutritionally rich base of Beef heart, Calf brain infusions, and Peptone mixture provide nitrogen, vitamins, minerals, and amino acids that support the growth of a variety of microorganisms. Disodium phosphate acts as a buffer and dextrose is the fermentable carbohydrate providing carbon and energy. Sodium chloride maintains the osmotic balance and bacteriological agar is the solidifying agent.

If 10% sterile defibrinated blood is added, the medium can be used for the cultivation and isolation of Histoplasma capsulatum. With the addition of antibiotics, BHI Agar can be used for the isolation of fungi. Brain Heart Infusion Agar with cycloheximide and chloramphenicol restrict growth of bacteria and saprophytic fungi. It is recommended for the isolation of fungi difficult to grow such as H. capsulatum and Blastomyces dermatiditis. Adding polysorbate to BHIA allows for identification of Mycobacterium avium-intracellular complex organisms and M. tuberculosis from blood cultures.

Occasionally BHIA plates are used for general sensitivity tests. However, it is not suitable to determine haemolytic reactions as this medium has a high dextrose concentration and it may give atypical readings. To prepare a selective medium for fungi, the sterilized and melted medium should be cooled to 45-50 °C before adding the appropriate antibiotics. Occasionally a small amount of sediment may appear which should be resuspended with a gentle swirl before dispensing.