Lowenstein Jensen (LJ) Medium I Purpose and Composition I Selective Media I Bacterial Culture Media скачать в хорошем качестве

Lowenstein Jensen (LJ) Medium I Purpose and Composition I Selective Media I Bacterial Culture Media

Lowenstein-Jensen Medium is an egg-based selective medium with malachite green, widely used for the isolation of Mycobacterium tuberculosis. Colonies appear rough, tough, and buff, making it a gold standard medium for TB culture. Lowenstein-Jensen (LJ) Medium is a selective egg-based medium used for the isolation and cultivation of Mycobacterium tuberculosis and other mycobacteria. It contains malachite green dye that inhibits most contaminants while permitting the slow-growing Mycobacterium to develop. 2. Purpose / Uses Primary selective medium for Mycobacterium tuberculosis complex from sputum and clinical samples. Also supports growth of M. bovis, M. africanum, and some non-tuberculous mycobacteria (NTM)*. Used in clinical microbiology, tuberculosis diagnosis, and drug susceptibility testing. Recommended by WHO for routine TB culture. 3. Composition (per liter, typical) Base: Potato flour + whole eggs (nutrient source and solidifying agent) Whole eggs – ~750 mL (enrichment + solidifying base). Mineral salt solution (KH₂PO₄, MgSO₄, Mg citrate, Asparagine, Glycerol) – provides essential nutrients. Potassium dihydrogen phosphate (KH₂PO₄) – 2.4 g (buffer). Magnesium sulfate (MgSO₄·7H₂O) – 0.24 g. Magnesium citrate – 0.6 g. Asparagine – 3.6 g (nitrogen source). Glycerol – 12 mL (carbon source; enhances growth of M. tuberculosis). Potato flour or starch – ~30 g (growth factor, provides moisture). Malachite green (0.025%) – selective agent; inhibits contaminating bacteria and fungi. Final pH: 7.2 ± 0.2 at 25 °C 4. Principle Egg base → provides proteins, fatty acids, and solidifies the medium. Glycerol → enhances growth of M. tuberculosis (but not M. bovis, which grows poorly). Malachite green → inhibits most other bacteria and fungi, making the medium selective. Slow growth: Colonies appear after 2–6 weeks due to slow metabolism of mycobacteria. 5. Colony Characteristics Mycobacterium tuberculosis: Rough, tough, and buff-colored colonies (classic description: “Rough, Tough, Buff”). M. bovis: Small, smooth, non-pigmented colonies; grows poorly due to glycerol sensitivity. Contaminants: Usually inhibited by malachite green. 6. Summary Lowenstein-Jensen (LJ) Medium (Selective Media): Purpose: Selective medium for isolation of Mycobacterium tuberculosis and other mycobacteria. Composition: Whole eggs, potato flour, asparagine, glycerol, mineral salts, malachite green. Key Point: M. tuberculosis grows as rough, tough, buff colonies after 2–6 weeks.