Brain Heart Infusion (BHI) broth is a general-purpose liquid medium used for the cultivation and maintenance of a wide variety of fastidious and non-fastidious microorganisms, including aerobic and anaerobic bacteria, yeast, and molds from a variety of clinical and non-clinical specimens.
The initial BHI was made by Rosenow, in which he added calf brain tissue to dextrose broth to grow streptococci. At present, various modifications of BHI broth are commercially available based on the intended use.
The medium contains proteose peptone and infusions from calf brain and beef heart which serve as sources of carbon, nitrogen, essential growth factors, amino acids and vitamins. Dextrose is used as a source of energy. Disodium phosphate helps in maintaining the buffering action of the medium whereas sodium chloride maintains the osmotic equilibrium of the medium.
Composition of Brain Heart Infusion (BHI) Broth
The quantity of the ingredients may vary depending upon the manufacturer; and the addition of some selective growth supplements; however, the basic ingredients remain the same.
|Ingredients||Gms / Litre|
|Calf brain, infusion from||200|
|Beef heart, infusion from||250|
|Final pH ( at 25°C)||7.4±0.2|
Procedure for preparation and storage of BHI Broth:
- Suspend 37.0 g of medium in 1 liter of distilled water.
- Heat if necessary to dissolve the medium completely.
- Dispense into bottles or tubes as desired.
- Sterilize by autoclaving at 15 Ibs (121° C) for 15 minutes.
- Label the side of each tube with the date of preparation and batch number.
- Store the culture medium at 2-8°C sealed in plastic bags to reduce the chances of contamination.
NOTE: The composition and method for preparation of media vary according to the manufacturer. Please refer to the instruction given by the manufacturer.
Storage conditions and Shelf life
Dehydrated medium can be stored at 10-30°C and use before the expiry date on the label. Prepared tubed or bottled medium needs to store in the dark and below 20°C.
Procedure for use:
- Allow medium to adjust to room temperature prior to inoculation.
- Lightly inoculate the broth using the test sample or with the organism of interest (for aerobic and others)
- For anaerobic organisms, prior to inoculation, pre-reduce the broth by placing the tubes in an anaerobic environment overnight at room temperature and then inoculate lightly.
- Incubate the tubes
- For aerobic organisms, incubate aerobically at 35°C with loose caps.
- For fastidious organisms such as Haemophilus species incubate in a CO2-enriched atmosphere at 35°C with a loose cap.
- For anaerobic organisms, incubate tubes anaerobically at 35°C with loose caps.
- Examination for the growth:
- For aerobic and others, examine tubes after 24 hours and at 48 hours. Reincubate tubes an additional 24 hours if required.
- For anaerobic cultures, examine tubes after 48 hours.
Interpretation of Results: After the incubation period examine tubes for turbidity which is an indication of growth. If desired, a loopful of the culture broth can then be sub-cultured onto an appropriate solid medium to observe colony morphology and further tests can be performed from the isolated colonies.
- For the culture of yeasts or fungi, a prolonged incubation period may be required to obtain good growth
- Since nutritional requirements of organisms vary, some strains may fail to grow or grow poorly in this medium.
Uses of Brain Heart Infusion Broth
Various modifications of BHI serve various processes. Addition of one or more growth supplements facilitates the growth of the desired organism. Some common modifications and its usage are described below:
|BHI with Fildes||Used for cultivating capsular strains of Haemophilus influenzae|
|BHI with Hemin and Viatmin K||Primarily used for anaerobic organism cultivation and the recovery of fastidious anaerobic organisms.|
|BHI broth||1. To prepare inoculum suspensions for antibiotic susceptibility testing, microdilution, minimal inhibitory concentration (MIC) |
2. As a medium for blood cultures
|BHI with 10% defibrinated sheep blood||Useful for isolation and cultivation of Histoplasma capsulatum and other fungi|
|BHI with 0.1% agar||Used for the cultivation of anaerobes|