Haemophilus influenzae requires which growth factors to grow in culture?

• A. X (hemin) and V (NAD+)
• B. Only X (hemin)
• C. Only V (NAD+)
• D. Neither X nor V

Answer: (A)

Haemophilus influenzae cannot make heme or NAD on its own, so it needs both external growth factors to grow. The X factor is hemin, a component required for the bacterium’s cytochromes and energy metabolism, while the V factor is NAD+. Both are essential; supplying only one of them won’t support growth. In culture, chocolate agar provides both by lysing red blood cells with heat, releasing X and V, which is why this medium supports growth. On standard blood agar, growth can be limited unless another organism (like Staphylococcus aureus) supplies NAD through satellitism, illustrating the need for both factors. Therefore, Haemophilus influenzae requires both X and V for growth.