Sterility Check of Culture Isolates

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

3. Vortex the MGIT tube well, unscrew the tube cap and aliquot the sample broth using a sterile, disposable pipette/inoculation loop. Remove about 200 μl of broth (~ 4 drops) and inoculate the BHI agar.

4. Incubate the agar plate in the incubator at 37 °C  for 72 hours.

Results:

1. Growth in 24 – 48 hours (Contamination)​
2. No Growth (Contamination free) ​

Resource

Mycobacteriology Laboratory Manual

Assessment