A 45-year-old man with confirmed pulmonary TB is found to have isoniazid (INH) resistance only on drug susceptibility testing. His sputum smear remains positive at 2 months. According to RNTCP/NTEP 2022 guidelines for HR-TB (isoniazid-resistant TB), what is the standard regimen?

• A Continue standard HRZE for 6 months
• B 6RZELfx — rifampicin, pyrazinamide, ethambutol, levofloxacin for 6 months ✓
• C Bedaquiline + pretomanid + linezolid (BPaL) for 6 months
• D Streptomycin + ethambutol + rifampicin for 12 months

Explanation

For isoniazid-resistant TB (Hr-TB, susceptible to rifampicin), WHO 2022 guidelines recommend a 6-month regimen of rifampicin (R), pyrazinamide (Z), ethambutol (E), and levofloxacin (Lfx) — abbreviated 6RZELfx. This replaces the inadequate continued standard HRZE regimen which includes INH to which the strain is resistant. The BPaL/BPaLM regimens are reserved for XDR-TB. Streptomycin-based regimens are outdated and not recommended.

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

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