Incubation of MGIT Tubes

After inoculating the tubes, they have to be incubated in the BACTEC MGIT 960 instrument to check if there is mycobacterial growth after the stipulated time.

The steps for incubating MGIT tubes for TB cultures are as follows:

1. Enter the inoculated MGIT tubes into BACTEC MGIT 960 instrument.

2. Scan the tube bar code and specimen bar code (if available​) (Figure 1).

Figure 1: Scanning the tube bar code

3. Insert tubes into the instrument in the slots assigned (indicated by a green light​) (Figure 2).

Figure 2: Slots with green light indicated for inserting the tubes

4. The tubes are incubated in the MGIT 960 instrument at 37±1°C.  

a. The temperature readout of each drawer must be checked daily.

b. Since the optimum temperature for growth of M. tuberculosis is 37ºC, make sure the temperature is close to 37ºC.

5. Fluorescence in each tube is measured every 60 minutes by the photodetector assembly.

6. Tubes are detected Positive or Negative, based on the fluorescence.​

7. MGIT tubes should be incubated until the instrument flags them positive. After a maximum of six weeks, the instrument flags the tubes negative if there is no growth.

8. Some species such as M. ulcerans and M. genavense may require extended incubation time; if such species are expected to be present, incubate further for 2-3 weeks.

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

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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