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Inoculum Preparation from MGIT Positive Culture
Learning Objectives(1-2 Days and 3-5 Days Procedure)
Inoculum Preparation for Drug-containing Tube (1-2 days)
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DST must not be set up on the same day an MGIT tube signals positive (0 Day).
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If the culture is worked up one or two days after signalling positive, it can be used directly to inoculate the MGIT tubes for DST.
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Mix well (vortex) the confirmed MTB pure culture isolate to break up the clumps. Leave the tube undisturbed for about 5-10 minutes to let big clumps settle on the bottom.
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Use the undiluted supernatant for inoculation of the drug tube set.
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Aseptically add 0.5 ml of the well-mixed culture suspension (inoculum) into each drug-containing tube using a pipette. Do not add to the growth control (GC).
Inoculum Preparation for Growth Control (GC) Tube (1-2 days)
For the growth control (GC) tube, first, dilute the test culture suspension 1:100 by adding 0.1 ml of the test culture suspension to 10.0 ml of sterile saline. Mix well by inverting the tube 5-6 times. Use this diluted suspension to add 0.5 ml into the growth control tube.
Inoculum Preparation for Drug-containing Tube (3-5 days)
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If the culture is used to set up DST between three and five days after signaling positive.
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Mix well (vortex) the confirmed MTB pure culture isolates to break up the clumps. Leave the tube undisturbed for about 5-10 minutes to let big clumps settle on the bottom.
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Use the undiluted supernatant for preparation of 1:5 dilution, 1 ml of MGIT broth in 4 ml of sterile saline (1:5 dilution).
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Use this well-mixed diluted culture for inoculation of the drug tube set.
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Aseptically add 0.5 ml of the well-mixed culture suspension (inoculum) into each drug-containing tube using a pipette. Do not add to the growth control (GC).
Inoculum Preparation for Growth Control (GC) Tube (3-5 days)
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For the growth control (GC) tube, first, dilute the test culture suspension 1:100 from 1:5 diluted MGIT tube. by adding 0.1 ml of the test culture suspension to 10.0 ml of sterile saline. Mix well by inverting the tube 5-6 times. Use this diluted suspension to add 0.5 ml into the growth control tube.
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A tube that has been positive for more than 5 days should not be subjected to DST. Instead, it should be subcultured in a fresh MGIT tube supplemented with MGIT 960 Growth Supplement and should be tested in an MGIT 960 instrument until it is positive.
3 Use this tube from one to five days of instrument positivity as described above.
Resource
Mycobacteriology Laboratory Manual
Assessment
Question |
Answer 1 |
Answer 2 |
Answer 3 |
Answer 4 |
Correct answer |
Correct explanation |
Page id |
Part of Pre-test |
Part of Post-te |
DST must not be set up on the same day an MGIT tube signals positive (0 Day). | True | False | True | DST must not be set up on the same day an MGIT tube signals positive (0 Day). |
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