Culture medium for cultivation of mycobacterium is: September 2005 & 2011
High-Yield Explanation
Ans. D: LJ medium Diagnosis of tuberculosis Microscopy - Rapid diagnosis - Low sensitivity. Concentration may increase sensitivity up to hundred folds - Can not differentiate tuberculosis and non-tuberculosis mycobacteria - False positive results - Samples must always be studied with one positive and one negative control Culture - The gold standard method for tb diagnosis Culture in LJ media takes 3 to 6 weeks - Commonly used rapid culture systems have disadvantages: Radioactive, expensive, blood containing samples give false results All culture methods require decontamination When grown on LJ medium, M. tuberculosis appears as brown, granular colonies (sometimes called "buff, rough and tough"). The media must be incubated for a significant length of time, usually four weeks, due to the slow doubling time of M. tuberculosis compared with other bacteria (15-20 hours). Lowenstein-Jensen (g) medium is most widely used for tuberculosis culture. LJ medium containing glycerol ours the growth of M. tuberculosis while LJ medium without glycerol but containing pyruvate encourages the growth of M. bovis. Both should be used in countries or regions where patients may be infected with either organism. Ingredients Mineral salt solution Potassium dihydrogen phosphate anhydrous (1(1-12PO4) 2.4g Magnesium sulphate (MgSO4. 7H20) 0.24g Magnesium citrate 0.6g Asparagine 3.6g Glycerol (reagent grade) 12m1 Distilled water 600m1