Kirchner's T.B. Medium

LAB 123

Description

The cultivation of non-sputum specimens for mycobacteria requires special attention. Specimens such as C.S.F., tissue or body fluids obtained by surgical procedures are not easily repeated and may contain small numbers of mycobacteria. It is important, therefore, that as large a portion of specimen as possible be inoculated into suitable growth media.

Historically, such specimens were inoculated into guinea pigs; however improvements in culture methods have led to a situation where comparable results, can be obtained from the use of liquid culture media.

Selective Kirchner's Medium is a liquid culture media, which is made selective by the addition of an antibiotic cocktail, and has been shown to be sufficient in the recovery of mycobacteria from non-sputum specimens.

References

Kirchner, O., (1932). Erfahrungen bei diagnosticher Verwendung Tiefenkulter. Sbl fur Bact. Abt 1. Originale 124, 409-412.

Marks, J. (1972), Ending the routine guinea pig test. Tubercle (19 53: 31-34.

Mitchison, D.A. Allen, B.W., Manickavasagar, D. (1983). Selec Kirchner's medium in the culture of specimens other than sputum mycobacteria. J.Clin. Path. 36: 1357-1361.

Method for reconstitution

Weigh 17.4 grams disperse in 1 litre deionised water, add 20ml Glycerol A.R. Allow the mixture to soak for 10 minutes, swirl to mix and sterilise by autoclaving at 121°C for 10 minutes. Allow the medium to cool and supplement with 1ml sterile heat in activated horse serum and 2 vials of X124, if required. Aseptically dispense in 9ml volumes into sterile Macartney bottles.

Appearance: Pale red, clear fluid. pH: 7.0 ± 0.2

Minimum Q.C. organisms: M. tuberculosis (H37RV strain) E. coli (inhibition) NCIMB 50034 Candida albicans. (inhibition) NCIMB 50010

Storage of Prepared Medium: up to 3 months at 2-8˚C in the dark.

Inoculation: Kirchner's Medium is suitable for the cultivation of mycobacteria from the following specimens:

Pre-treatment Required

Concentration and acid or alkali decontamination.

None.

Disintegration followed by acid or alkali decontamination, if necessary.

The acidified or alkaline de-contaminated material may be added directly to the Kirchner medium. The pH is then adjusted using the appropriate normal solution observing colour or indicator.

Although Kirchner's Medium has been shown to give higher isolation rates than solid media, it is recommended that specimens should also be inoculated onto Lowenstein Jensens slopes for the following reasons: - Growth suitable for further characterisation may be obtained more rapidly - Some Mycobacterium species including M. intracellulare, M .kansasii and M. scrofulaceum may be inhibited by the antibiotic cocktail.