Blood Agar (Base) 500g

Description

This culture medium can be used without blood e.g. for setting up blood cultures (UPDYKE 1970) and as a base for preparing special culture media
The medium complies with the recommendations of APHA (1992) for the examination of foodstuffs.

Principle
Microbiological method

Mode of Action
This culture medium represents a rich nutrient base, which provides optimal growth conditions for all relevant microorganisms. The pH value of 6.8 stabilizes the red blood corpuscles and favours the formation of clear haemolysis zones (NORTON 1932). Fresh, defibrinated sheep blood is most suitable for determining haemolysis forms.
Boiled blood agar (“chocolate agar”) is an extremely rich culture medium and can be prepared by heating after the blood has been added.
If the culture medium base is to be used without blood, the pH should, however, be adjusted to 7.2 to 7.4 since most bacterial colonies appear somewhat earlier and grow better in a slightly alkaline medium.

TARSHIS and FRISH (1951) recommended addition of 1% glycerol and 25 % human blood when isolating tubercle bacilli from sputum, since recognizable mycobacteria colonies grow from even minimal amounts of sample material.
HOSTY et al. (1953) reported, however, that 0.1 % glycerol and 2.5 % human blood together with 100 IU/mol of penicillin as a selective agent are sufficient. According to SONDAG et al. (1977) and BLACK a. VAN BUSKIRK (1973), addition of 5 mg/l gentamicin (e.g. 0.1 ml gentamicin solution) to blood agar permits selective cultivation of Streptococcus pneumoniae and other Streptococci as well as bacterioides, Clostridium and
yeasts.
For the selective cultivation of Aeromonas MISHRA et al. (1987) recommend an ampicillin sheep blood agar (ASBA 30).

Typical Composition (g/litre)
Nutrient substrate (heart extract and peptones) 20.0;
sodium chloride 5.0:
agar-agar 15.0.

Also to be added:
Blood 50-80 ml.