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3. Let stand for 15 minutes. Remove the swab with forceps, squeezing the
liquid out of the swab and discarding it.
4. Fill the tube with phosphate buffer and mix
5. Centrifuge at 3000xg for 15-20 minutes.
6. Discard the supernatant fluid and resuspend the sediment in 1-2 ml sterile
buffer. Use this suspension for smear and culture.
6.5 Tissue
1. Homogenize the tissue in a tissue grinder with a small quantity of sterile
saline or water (2-4 ml).
2. Decontaminate the homogenized specimen using NALC-NaOH procedure as
in sputum.
3. Resuspend the sediment with phosphate buffer
4. If the tissue grinder is not available, use a mortar and pestle.
5. Tissue may also be placed in a Petri dish with sterile water (2-4 ml) and be
torn apart with the help of two sterile needles.
6.6 Urine
Isolation of mycobacteria from urine specimens using MGIT has not been validated.
1. Aliquot the entire volume in several centrifuge tubes
2. Concentrate the specimen by centrifugation for at least 20-25 minutes
3. Resuspend the pellet in each tube with 1-2 ml of sterile water and pool
together
4. Decontaminate using 4% NaOH as for sputum
6.7 Other body fluids (CSF, synovial fluid and pleural fluid)
As these fluids are collected usually under aseptic conditions, they require only
milder decontamination
1. If the specimen volume is more than 10 ml, concentrate by centrifugation at
about 3000x g for 15-20 minutes
2. Liquefy thick or mucoid specimens prior to centrifugation by adding NALC
powder (50-100 mg).
3. Resuspend the sediment in about 5 ml of saline
4. Mix and decontaminate as for sputum
6.8 Blood
Isolation of mycobacteria from blood specimens by MGIT 960 has not been
evaluated thoroughly. A few published studies have used blood after lysis
centrifugation. Ideally BACTEC Myco/F Lytic medium is recommended for isolation
of mycobacteria from blood samples.
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