Inoculation of MGIT Tubes

Mycobacteria Growth Indicator Tube (MGIT) contains a modified Middlebrook 7H9 broth base. When supplemented with MGIT Growth Supplement and PANTA, it provides an optimum medium for the growth of a majority of mycobacterial species. All types of specimens, pulmonary as well as extra-pulmonary (except blood), can be inoculated into MGIT for primary isolation of mycobacteria.

The steps for inoculating MGIT tubes are elaborated below:

1. Using a sterile transfer pipette, add 0.5 ml of the processed sample to a 7 ml MGIT tube (0.8 ml of PANTA-growth supplement mixture​ already added).
2. Tightly recap the tube and invert gently several times to mix well.
3. Recap and swab the exterior of each tube with disinfectant-soaked gauze (use individual swabs); ensure the disinfectant does not flow into the tube.
4. Leave the inoculated tubes at room temperature for 30 minutes.

Figure: Micropipette that will be used to add processed sputum specimen to the prepared MGIT tube

Precautions

• Do not add more than 0.5 ml of processed specimen.
• Volumes greater than 0.5 ml may alter the pH of the medium and result in false-positive fluorescence.
• Use a separate pipette or pipette tip for each specimen.
• Always recap the tube tightly, as loose caps may affect the detection of fluorescence.

Please click the video below to see the full procedure for inoculating and incubating MGIT tubes for TB cultures:

https://empowerschoolofhealth-my.sharepoint.com/:v:/g/personal/admin_empowerschoolofhealth_org/EXh5-goFTP5PvXwEDDp-r4UBvpE3fW4G4OmBRzP296LfTg?e=keEf8t

Resources

• MGIT Procedure Manual, Mycobacteria Growth Indicator Tube (MGIT) Culture and Drug Susceptibility Demonstration Projects, FIND Training Manual.

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