Brain Heart Infusion Agar

 

Code: CB1/1010

 

Description

A general purpose nutritious agar base. This medium was first used for the isolation of dental pathogens.

The mixture of brain and heart infusions is particularly useful in the isolation of Actinomyces israeli and Histoplasma capsulatum. With the addition of 7% defibrinated blood the medium will support the growth of a wide range of fastidious organisms, the phosphate buffer will help neutralise the acids produced from the utilisation of glucose and thus maintain viability. The medium is not recommended for the determination of haemolytic reactions because of the glucose content.

 

Typical Formula g/l

 

BHI solids	17.5
Tryptose	10.0
Glucose	2.0
Sodium chloride	5.0
Disodium phosphate	2.5
Agar	12.0

 

pH: 7.4 ± 0.2

       

Method for reconstitution

Weigh 49 grams of powder, disperse in 1 litre of deionised water. Allow to stand for 10 minutes then swirl to mix. Sterilise by autoclaving at 121ºC for 15 minutes. Cool to 47ºC then pour into petri dishes.

 

Appearance: Pale Straw colour, clear gel.

 

 

Minimum Q.C. organisms:  

S.aureus  NCIMB 50080

E.coli  NCIMB 50034

 

Storage of Prepared Medium: Plates -up to 7 days at 2-8ºC in the dark. Capped container - up to 3 months at 15-20ºC in the dark. Inoculation: Surface, streaking out to single colonies.

Incubation: Time and temperature to suit specimen/organisms.

 

Growth characteristics (with horse blood)	Colony size	Shape of organism (mm)	Surface colour
S.aureus	1.0-1.5	CV.E.G.	White/golden
Other staphylococci	0.5-1.5	CV.E.G.	White/yellow
Str. pyogenes	0.5-1.0	CV.E.G.	White
S. milleri	P.P.-0.1	CV.E.G.	Transp. (White)
E. faecalis	1.0-1.25	CV.E.G.	Grey/green
Str. pneumoniae	0.5-1.0	F.E.G.	Grey/green
E. coli	2.0-3.0	CV.E.G.	Grey
Ps.aeruginosa	2.0-4.0	F.CR.D.	Grey

 

 

References

Roseburg. T., Epps, L. J. and Clarke, A. R. 1944. A study of the isolation, cultivation and pathogenicity of Actinomyces israeli recovered from the human mouth and from actinomycosis in man. J. inf. Dis., 74: 131-149.

Howell, E. 1948 Efficiency of methods of isolation of Histoplasma capsulatum. Pbl. Hlth. Rep. 63: 173-178. 3/108