152 / 276
4.2 Decontamination of extra pulmonary samples
Most of the extra pulmonary specimens are paucibacillary in nature.
Hence, they require milder decontamination. When using solid culture for primary
isolation of tubercle bacilli from these specimens, it is preferable to use multiple
media including one liquid medium made selective by the use of specific
antibiotics that inhibit the growth of other micro organisms. The media include,
LJ, LJ with sodium pyruvate (LJ
Sodium pyruvate facilitates the growth of
M. bovis
. Antibiotics incorporated in the
liquid medium include polymixinB, amphotericin B, carbenicillin and trimethoprim
(PACT) and vancomycin.
Preparation of media
LJ MEDIUM WITH SODIUM PYRUVATE
LJ medium is enriched with 0.5% sodium pyruvate. In the preparation of the
mineral salt solution, glycerol is omitted and 8.0g sodium pyruvate is added for
every 600 ml. This is added to 1 litre of egg fluid, mixed well and distributed.
(For culture of extra-pulmonary specimens
)
Disodium hydrogen phosphate, Na
2
HPO
4
.12H
2
O, A.R. 19.0 g (7.5g of anhydrous
salt)
Potassium dihydrogen phosphate, KH
2
PO
4
, A.R. 2.0 g
Magnesium sulphate, MgSO
4
.7H
2
O, A.R. 0.6 g
Sodium citrate 2.5 g
L-asparagine 5.0 g
Casein hydrolysate (Bactocasitone) 0.5 g
Glycerol 20.0ml
Phenol Red, 0.4% solution 3.0 ml
Distilled water, to 1 litre
Check pH to 6.9 7.2
Autoclave at 15 lbs/15 minutes
Then add aseptically the following:
Polymyxin B (20,000 units) 31 mg
Carbenicillin 100 mg
Trimethoprim 10 mg
Amphotericin B, solubilised 10 mg
Dissolve the above in 5 ml sterile distilled water before addition
145