This is an egg-based medium for the isolation and presumptive identification of Mycobacterium spp., particularly Mycobacterium tuberculosis. Designed for use with NaOH treated samples which are neutralised using known buffering solutions to achieve a pH of 6.8 to 7.0 and which are inoculated directly onto LJ media after concentration by centrifugation.
NB: this media will NOT isolate M.bovis which requires the addition of pyruvate as a growth supplement.This is normally overcome by the inclusion of a pyruvate slope. Based on the original formulation of Lowenstein that was subsequently modified by Jensen, the medium contains glycerol and egg which provide the required protein and fatty acids. The coagulation of the egg albumin during preparation also provides a solid surface for inoculation purposes. Malachite green is incorporated into the medium to inhibit contaminating organisms other than the mycobacteria that may still be present in the specimen after decontamination. Lowenstein-Jensen slopes should be inoculated with pre-treated specimens and incubated at 35-37°C for 8 weeks in 5-10% CO2. Container caps should be left loose for the first week of incubation to allow for circulation of the carbon dioxide as this will help to stimulate growth. Caps should then be tightened to prevent any dehydration of the medium.
