COLUMBIA BLOOD AGAR BASE

Columbia Blood Agar Base was devised by Ellner et al. This medium promotes typical colonial morphology; better pigment production and more sharply defined haemolytic reactions. Fildes found that Nutrient Agar supplemented with a digest of sheep blood supplied both of these factors and the medium would support the growth of H. influenzae. Sheep blood permits the detection of haemolysis and also provides heme (X factor) which is required for the growth of many bacteria. However, it is devoid of V factor (Nicotinamide adenine dinucleotide) and hence Haemophilus influenzae which needs both the X and V factors, will not grow on this medium. The inclusion of bacitracin makes the enriched Columbia Agar Medium selective for the isolation of Haemophilus species from clinical specimens, especially from upper respiratory tract. Columbia Agar Base is used as the base for the media containing blood and for selective media formulations in which different combinations of antimicrobial agents are used as additives.
Columbia Agar Base with added sterile serum provides an efficient medium for Corynebacterium diphtheriae virulence test medium. After following the established technique for C. diphtheriae, lines of toxin-antitoxin precipitation are clearly visible in 48 hours. Many pathogens require carbon dioxide; therefore, plates may be incubated in an atmosphere containing approximately 3-10% CO2.
Precaution: Brucella cultures are highly infective and must be handled carefully; incubate in 5-10% CO2. Campylobacter species are best grown at 42?C in a micro aerophillic atmosphere. Plates with Gardenerella supplements plates should be incubated at 35?C for 48 hours containing 7% CO2.

for preparation of various selective & identi?cation media & isolation of organisms from clinical specimens