Mycobacterium tuberculosis survives within macrophage phagosomes by a specific mechanism. The bacterial protein that prevents phagosome acidification and lysosome fusion is:

• A ESAT-6 forming pores in the phagosome membrane to escape into cytosol
• B Lipoarabinomannan (LAM) blocking PI3P-dependent recruitment of EEA1 ✓
• C Catalase-peroxidase (KatG) neutralizing reactive oxygen species
• D Cord factor (trehalose-6,6-dimycolate) inhibiting oxidative phosphorylation

Explanation

Mannose-capped lipoarabinomannan (ManLAM) on the MTB cell wall inhibits the PI3-kinase VPS34 that generates PI3P (phosphatidylinositol 3-phosphate), preventing the recruitment of EEA1 (early endosome antigen 1) which is essential for phagosome maturation and acidification; this blocks phagolysosome fusion. ESAT-6 is a secreted protein that perforates phagosomal membranes to allow mycobacterial escape into the cytoplasm, relevant in some macrophage types. KatG destroys H2O2 and is required for INH activation (INH resistance when mutated). Cord factor inhibits leukocyte migration and mitochondrial oxidative phosphorylation.

Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.