Which medium would not be routinely used to culture Mycobacterium spp.?

• A. Lowenstein-Jensen
• B. Middlebrook II
• C. Chocolate agar
• D. Lowenstein-Jensen-Gruft

Answer: (C)

Understanding how Mycobacterium species are cultured hinges on providing a slow, selective environment with the nutrients they need. Lowenstein-Jensen and Middlebrook II are classic, routinely used media for mycobacteria because they supply the unique lipid-rich nutrients and conditions that support these slow growers while suppressing many contaminants. The Lowenstein-Jensen-Gruft modification is another specialized form of a mycobacterial medium designed to optimize growth and reduce contamination.

Chocolate agar, in contrast, is an enriched medium used for fastidious organisms such as Haemophilus and Neisseria, relying on factors released from lysed blood. It does not offer the nutrient balance or the selective properties needed for Mycobacterium spp., and it does not support their slow, careful growth pattern. Therefore, chocolate agar would not be routinely used to culture these bacteria.