The BACTEC MGIT 960 system is used for mycobacterial culture and phenotypic drug susceptibility testing. Which principle does it use to detect mycobacterial growth?
- A Colorimetric change of a pH indicator due to CO2 production
- B Direct visualization of cord formation under an automated microscope
- C Decrease in oxygen consumption measured by a fluorescent quenching sensor at the bottom of the tube ✓
- D Measurement of radioactive 14CO2 released from labeled palmitic acid
Correct answer: C. Decrease in oxygen consumption measured by a fluorescent quenching sensor at the bottom of the tube
Explanation
BACTEC MGIT uses Middlebrook 7H9 broth with a silicone-based fluorescent oxygen sensor at the tube bottom. Mycobacterial growth consumes oxygen, increasing fluorescence, which the MGIT instrument reads automatically. The older BACTEC 460 used radioactive 14B-palmitic acid (distractor D). MODS uses microscopy (distractor B). Colorimetric systems (distractor A) describe blood culture systems like BacT/ALERT.
Reference: Forbes Bailey & Scott's Diagnostic Microbiology, 15th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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