01/08/2026
The 𝗟ö𝘄𝗲𝗻𝘀𝘁𝗲𝗶𝗻-𝗝𝗲𝗻𝘀𝗲𝗻 (𝗟𝗝) 𝗺𝗲𝗱𝗶𝘂𝗺 is a solid, egg-based selective growth medium primarily used to cultivate and isolate Mycobacterium tuberculosis and other mycobacterial species from clinical specimens. It relies on heat coagulation (inspissation) rather than agar for solidification.
𝗖𝗼𝗺𝗽𝗼𝘀𝗶𝘁𝗶𝗼𝗻 & 𝗞𝗲𝘆 𝗜𝗻𝗴𝗿𝗲𝗱𝗶𝗲𝗻𝘁𝘀
⁃ 𝗘𝗴𝗴 𝗦𝘂𝘀𝗽𝗲𝗻𝘀𝗶𝗼𝗻: Provides essential proteins and fatty acids for metabolism.
⁃ 𝗠𝗮𝗹𝗮𝗰𝗵𝗶𝘁𝗲 𝗚𝗿𝗲𝗲𝗻: Acts as a selective dye to inhibit unwanted contaminating bacteria.
⁃ 𝗟-𝗔𝘀𝗽𝗮𝗿𝗮𝗴𝗶𝗻𝗲 & 𝗣𝗼𝘁𝗮𝘁𝗼 𝗙𝗹𝗼𝘂𝗿: Supplies nitrogen, vitamins, and carbohydrates.
⁃ 𝗚𝗹𝘆𝗰𝗲𝗿𝗼𝗹: Enhances the growth of human-type tubercle bacilli (M. tuberculosis).
⁃ 𝗠𝗶𝗻𝗲𝗿𝗮𝗹 𝗦𝗮𝗹𝘁𝘀: Maintain osmotic balance and buffering capacity.
𝗣𝗿𝗶𝗻𝗰𝗶𝗽𝗹𝗲
Egg albumin coagulates at roughly 85°C to form a solid slanted surface.Lipid-rich mycobacterial cell walls resist the malachite green dye, allowing slow-growing mycobacteria to survive while other contaminants die.
𝗖𝗼𝗹𝗼𝗻𝘆 𝗖𝗵𝗮𝗿𝗮𝗰𝘁𝗲𝗿𝗶𝘀𝘁𝗶𝗰𝘀 & 𝗜𝗻𝗰𝘂𝗯𝗮𝘁𝗶𝗼𝗻
⁃ Incubation Temperature: 35°C to 37°C.
⁃ Growth Time: Slow growth requires 3 to 8 weeks due to a long doubling time.
⁃ Colony Morphology: Rough, dry, tough, and buff-colored (often cauliflower-like).
𝗨𝘀𝗲𝘀
⁃ Primary isolation and cultivation of Mycobacterium tuberculosis.
⁃ Drug susceptibility testing for tuberculosis strains.
⁃ Differentiation tests (e.g., niacin testing).