What is a defining feature of CAP (CHOC) media?

The defining feature of CAP (Chocolate) media is that it features lysed red cells and appears brown. This type of media is enriched to support the growth of fastidious organisms, particularly those that require additional factors that are released from red blood cells when they are lysed. The process of lysing red cells allows for nutrients, such as hemin (X factor) and nicotinamide adenine dinucleotide (NAD or V factor), to be available in the medium, which is essential for the growth of certain bacteria like Neisseria gonorrhoeae and Haemophilus species.

The appearance of CAP media as brown is due to the denaturation of hemoglobin within the red cells during the heating process used to create the medium, which leads to its characteristic color. This alteration distinguishes it from other media types, such as blood agar, which contains intact red blood cells. The presence of lysed red cells means that CAP media can provide an environment conducive to the growth of specific bacteria that may not thrive on standard media with intact red cells.