Chocolate agar (CHOC) or chocolate blood agar (CBA) - is a non-selective, enriched growth medium. It is a variant of the blood agar plate.10% of fresh sheep blood is heated at 80°C by the lysis of RBcC cells . It contains red blood cells, which have been lysed by heating very slowly to 80 °C. Chocolate agar is used for growing fastidious respiratory bacteria, such as Haemophilus influenzae. These bacteria need growth factors, like NAD and hemin, which are inside red blood cells; thus, a prerequisite to growth is lysis of the red blood cells. The agar is named for the color and contains no actual chocolate.
Chocolate agar alone is non-selective, however with the addition of Bacitracin the media becomes selective, most critically, for the genus Haemophilus. A further variant containing an assortment of antibiotics selects for Neisseria.
Famous quotes containing the word chocolate:
“The man who invented Eskimo Pie made a million dollars, so one is told, but E.E. Cummings, whose verse has been appearing off and on for three years now, and whose experiments should not be more appalling to those interested in poetry than the experiment of surrounding ice-cream with a layer of chocolate was to those interested in soda fountains, has hardly made a dent in the doughy minds of our so-called poetry lovers.”
—John Dos Passos (1896–1970)