1. Isolates can be grown on solid or liquid media before being tested in the MGIT DST.

Revival of the frozen cultures 

The MGIT system automatically and continuously incubates and monitors tubes once they are placed in a station; there is no need to remove the tubes from the instrument. 

Cultures during incubation:

1. Cultures remain in their stations until signalled “positive”, or if no growth is detected after 42 days incubation, are signalled “negative”. 

2. If an instrument-positive tube is determined to be smear-negative for either mycobacteria or contaminants, the tube may be re-entered into the instrument, but within 5 hours of removal.

A sterility check of growth is ascertained to differentiate M. tuberculosis from other contaminants in MGIT-positive tubes. 

BHI (Brain Heart Infusion) Agar plates are used for sterility checks using the following steps:

1. Divide the plate into 4 quadrants so that four specimens can be subcultured onto one plate. 

2. Label the plate with specimen ID