Which organism requires both hemin (X factor) and NAD (V factor) for growth?

• A. Haemophilus aegyptius
• B. Haemophilus influenzae
• C. Neisseria meningitidis
• D. Moraxella catarrhalis

Answer: (A)

Growth of certain bacteria depends on preformed growth factors provided by the medium. Hemin, called X factor, and NAD, called V factor, are nutrients that some organisms cannot synthesize themselves, so they must obtain both from their surroundings. Haemophilus species, in particular, require both X and V to grow. They are often cultured on chocolate agar or other media that supply or release these factors, because heating or lysing red blood cells releases X and V factors for them to use. Among the listed organisms, only a Haemophilus species truly needs both X and V to grow, which is why Haemophilus aegyptius (and other Haemophilus species) is the correct example. Neisseria meningitidis and Moraxella catarrhalis do not require both factors in the same way and can grow on standard enriched media without needing the two growth factors together.