A sputum sample sent for AFB culture grows mycobacteria on Lowenstein-Jensen (LJ) medium after 6 weeks as rough, buff-coloured colonies. Line probe assay (LPA) shows a mutation in the rpoB gene (S450L substitution). The most appropriate initial drug regimen is:
- A Continue standard HRZE (Category I) regimen
- B Bedaquiline, pretomanid, and linezolid (BPaL regimen)
- C Bedaquiline, linezolid, cycloserine and clofazimine (shorter MDR-TB regimen) ✓
- D Amikacin, kanamycin and para-aminosalicylic acid
Correct answer: C. Bedaquiline, linezolid, cycloserine and clofazimine (shorter MDR-TB regimen)
Explanation
rpoB gene mutation (particularly S450L, formerly S531L) confers rifampicin resistance, which is a proxy marker for MDR-TB (resistant to both isoniazid and rifampicin). The current WHO-recommended shorter MDR-TB regimen includes bedaquiline, linezolid, cycloserine (or terizidone), and clofazimine for 9–12 months. BPaL (bedaquiline-pretomanid-linezolid) is the ZeNix/TB-PRACTECAL regimen for XDR-TB or treatment-intolerant MDR-TB. Standard HRZE is inappropriate for confirmed rifampicin resistance.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.