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Test Procedure

1. Bring the Lowenstein-Jensen medium slant to room

temperature.

2. Label the Lowenstein-Jensen medium slant appropriately.

3. Draw 10 µL of the decontaminated and concentrated

specimen from the reconstituted pellet with a sterile

calibrated loop and plate it on the Lowenstein-Jensen

medium slant aseptically.

4. For quantitative evaluation prepare bacterial suspension to match McFariland 0.5 standard, dilute this

1:10000 and Seed 100 µL on the Lowenstein-Jensen

medium slant aseptically (seed stock consists of

approx.-15000 organisms/mL).

5. Close the Lowenstein-Jensen slant cap tightly and

incubate at 37 ± 0.5oC.

6. Observe for growth weekly till 8 weeks.

Interpretation of Results

1. Mycobacterium tuberculosis colonies may be detected

from third week onwards up to 8 weeks. The colonies

are characterized by rough granular buff colored

growth, which has an initial size of 1–3 mm and fullgrown size of 5–8 mm.

Remarks

1. Discolored, dislodged, or contaminated medium

should not be used.

2. Improper decontamination and concentration

procedure will yield erroneous results.

3. Treat the specimens and used slants by immersing in

2% activated glutaraldehyde for at least 2 hours before

incineration and disposal.

4. Good laboratory practices and hazard precautions

must be observed at all times.

5. In specimens from patients already on antitubercular

drugs, the initial growth may be further delayed.

6. Growth on the Lowenstein-Jensen slant within the

first week post inoculation usually indicates atypical

Mycobacterium or contamination due to insufficient

decontamination of specimen.