Which agar plate effectively supports the growth of Haemophilus species that require V factor?

The correct choice is chocolate agar because it is specifically formulated to support the growth of fastidious organisms, including Haemophilus species that require the V factor (nicotinamide adenine dinucleotide, or NAD). Chocolate agar is enriched with lysed red blood cells, releasing intracellular nutrients such as hemin (factor X) and V factor, which are essential for the growth of these organisms. This medium creates an optimal environment for Haemophilus species, as they cannot produce these factors on their own and instead rely on their presence in the culture medium.

Other media mentioned, like blood agar made with sheep or horse red cells, do contain the essential nutrients but do not liberate the V factor due to the intact erythrocytes in these preparations. Therefore, while they may support some growth of certain bacteria, they are less effective for Haemophilus species compared to chocolate agar. Xylose agar, on the other hand, is designed for the isolation of enteric organisms and is not suitable for fastidious bacteria like Haemophilus, emphasizing chocolate agar’s specialized role in culturing these particular species.