For the disk diffusion testing of Haemophilus influenzae, the recommended medium is Mueller-Hinton base supplemented with which components?

• A. Chocolate agar
• B. Charcoal yeast extract agar
• C. Mueller-Hinton base supplemented with 5% sheep blood
• D. Mueller-Hinton base supplemented with hematin, NAD, and yeast extract

Answer: (D)

Haemophilus influenzae is a fastidious organism that requires specific growth factors to grow well in susceptibility testing. For disk diffusion, you start with a Mueller-Hinton base because it provides a consistent, standard medium for measuring zones of inhibition. But Haemophilus needs the X factor (hemin) and the V factor (NAD) to grow. Adding hematin supplies X, and NAD provides V, while yeast extract adds extra nutrients that support robust growth of this organism on the agar. This combination yields reliable, interpretable zones around antibiotic disks. Other media variants either rely on blood-containing or chocolate-enriched media to supply those factors indirectly, or are not the defined, standard setup used for Haemophilus susceptibility testing. So the suited medium is Mueller-Hinton base supplemented with hematin, NAD, and yeast extract.