1. Discolored, dislodged, contaminated or turbid

medium should not be used.

2. Improper decontamination and concentration

procedure will yield erroneous results.

3. Good laboratory practices and hazard precautions

must be observed at all times.

4. While observing growth in liquid medium, care needs

to be taken to differentiate between Mycobacterium

growth and specimen material’s own turbidity.

5. Treat the specimens and used slants by immersing

in 2% activated Glutaraldehyde for at least two hours

before incineration and disposal.

6. Preparation of Kirchner medium has to be carried out

just prior to inoculation of specimen or culture.

7. In specimens from patient, already on antitubercular

drugs, the initial growth may be further delayed.

Microbiology and Bacteriology 859

8. Growth on the Lowenstein-Jensen slant/Kirchner

medium within the first week postinoculation usually

indicates atypical Mycobacterium or contamination

due to insufficient decontamination of specimen.

9. All culture growth should be characterized based on

morphology, AFB stain and biochemical tests.

Radiometric media: Developed in 1970, represent

a significant improvement in the rapid isolation of

Mycobacterium tuberculosis. Detection time is directly

proportional to the number of metabolically active

bacteria present and the metabolic rate is influenced

by the type of specimen, number of organisms, therapy

status of patient, decontamination procedures and the

incubation temperature.

The average time for reporting the isolation of

Mycobacterium tuberculosis using radiometric technique

is reportedly 22 ± 9 days as compared to 31 ± 9 days for

solid media.