LöwensteinJensen

Löwenstein-Jensen medium, commonly abbreviated as LJ medium, is a solid egg-based culture medium used for isolation and growth of mycobacteria, especially members of the Mycobacterium tuberculosis complex. The medium is named after its developers, Löwenstein and Jensen. It is prepared from a base derived from dried egg components and contains a dye such as malachite green that suppresses many contaminating bacteria, along with a carbon source such as glycerol. The medium may be supplemented with additional nutrients to promote growth, and several variants exist with different glycerol contents or supplements.

Clinical use: LJ medium is employed to culture mycobacteria from clinical specimens, including sputum, skin, and tissue samples. Growth is slow, with visible colonies typically appearing after several weeks at 37°C. Colonies are usually dry, buff-colored and non-pigmented, though some strains may produce pigment under exposure to light.

Comparison and relevance: LJ is relatively inexpensive and robust, making it widely used in resource-limited settings. However, its slow growth and lower sensitivity compared with modern automated liquid culture systems have led many laboratories to adopt alternative media such as Middlebrook 7H10/7H11 or MGIT. It remains a standard teaching and reference medium in microbiology.

Safety: Work with LJ medium involves handling cultures of pathogenic mycobacteria and requires appropriate biosafety measures (BSL-2) and institutional approvals.