Haemophilus influenzae requires which two growth factors?

Haemophilus influenzae requires which two growth factors?

• A. Hemin and NAD
• B. Thiamine and NAD
• C. Iron and hemin
• D. NAD and biotin

Answer: (A)

Haemophilus influenzae is a fastidious bacterium that cannot synthesize certain growth factors on its own and must obtain them from the environment. It requires two specific supplements to grow: hemin, classified as the X factor, and nicotinamide adenine dinucleotide (NAD), known as the V factor. In the lab, providing these factors is why chocolate agar or blood agar supplemented or heated to lyse red blood cells supports growth, because such methods release X and V factors from the cells. Without both factors, the organism cannot grow. The other options don’t fit because thiamine is not required for Haemophilus growth, iron cannot substitute for NAD, and biotin is not involved in its growth requirements.

Haemophilus influenzae is a fastidious bacterium that cannot synthesize certain growth factors on its own and must obtain them from the environment. It requires two specific supplements to grow: hemin, classified as the X factor, and nicotinamide adenine dinucleotide (NAD), known as the V factor. In the lab, providing these factors is why chocolate agar or blood agar supplemented or heated to lyse red blood cells supports growth, because such methods release X and V factors from the cells. Without both factors, the organism cannot grow. The other options don’t fit because thiamine is not required for Haemophilus growth, iron cannot substitute for NAD, and biotin is not involved in its growth requirements.