Which feature of the BACTEC MGIT 960 system explains its shorter time to detection of M. tuberculosis compared with culture on Lowenstein-Jensen medium?

• A Radiometric detection of C14-labelled palmitate metabolism
• B In-built nucleic acid amplification targeting IS6110
• C Liquid Middlebrook 7H9 broth with a fluorescence-quenching oxygen sensor read daily ✓
• D Use of a solid egg-based medium enriched with glycerol and pyruvate

Explanation

MGIT 960 tubes contain liquid 7H9 broth with an oxygen-quenched fluorochrome at the base. Growing mycobacteria consume dissolved oxygen, fluorescence increases, and the instrument flags the tube, giving a mean time to positivity of roughly 10 to 14 days versus 3 to 6 weeks on LJ. Option A describes the older BACTEC 460TB radiometric system, which was largely withdrawn because of radioactive waste. MGIT has no built-in amplification.

Reference: Koneman's Color Atlas and Textbook of Diagnostic Microbiology, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.