Acidified Pyruvate Egg Medium

This is an egg-based medium for the isolation and presumptive identification of Mycobacterium spp.
Designed for use with NaOH treated samples which have sterile distilled water added at the end of the designated treatment time to “dilute” the effect of NaOH. This media will isolate most common mycobacteria including M.bovis. Based on the original formulation of Lowenstein that was subsequently modified by Jensen, the medium contains pyruvate and egg which provide the required protein and fatty acids. It differs from Lowenstein-Jensen Medium in that Sodium Pyruvate has replaced the Glycerol, which has been demonstrated to be inhibitory to some species, particularly M.bovis. 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.