Kirchner Medium Base

Principle And Interpretation

Mycobacterium tuberculosis is an acid-fast gram-positive aerobic bacteria involved in most cases of tuberculosis. Humans are the only reservoir for the bacterium. Many non-pathogenic Mycobacteria are components of the normal flora of humans, found most often in dry and oily locales. Kirschner Medium was first developed by Kirschner based on the formulation of Longs Medium (1) and further modified with addition of glycerol and enrichments for the cultivation of M.tuberculosis.

It is widely used for antibacterial test, for antituberculosis agents and sometimes in differential culture of M.tuberculosis from unhealthy materials. Broth medium can give results in a week or two; hence broth medium is widely used in cases where rapid results are needed. Kirschner medium contains two phosphates, a sulphate and citrate, which buffer the medium. Hence the medium can be directly inoculated without any prior neutralization. L-asparagine in the medium supports the growth of M.tuberculosis, as it is a good nutrient for the organism. Horse serum also promotes the growth of the organism. At first stage after inoculation of M. tuberculosis, granular colonies are observed at the bottom of the tube and as the incubation proceeds bacterial film will be formed on the surface, rendering the medium transparent. Poctri supplement acts as selective supplement for M. tuberculosis.