What this test measures
This test determines whether a cultured M. tuberculosis isolate is sensitive or resistant to clofazimine at the WHO-defined critical concentration. Clofazimine, originally a leprosy drug, has become a key oral companion drug in modern MDR-TB regimens, including the WHO-endorsed BPaLM regimen.
Clofazimine resistance is increasingly recognised and shares an efflux-pump mechanism (Rv0678 mutations) with bedaquiline — so clofazimine-resistant strains often have reduced bedaquiline susceptibility too.
Why it matters
India's NTEP has rolled out bedaquiline and now clofazimine-containing regimens for MDR-TB. Confirming susceptibility to clofazimine before starting these regimens prevents treatment failure and protects bedaquiline, the single most important new TB drug. Resistance to clofazimine therefore has implications far beyond the drug itself — it can compromise the entire backbone of modern MDR-TB therapy.
Clofazimine is generally well-tolerated but causes reddish-brown skin discoloration (reversible on stopping) which can affect adherence.
How to prepare
A positive M. tuberculosis culture (MGIT or LJ) is required. If not yet available, sputum samples must be collected for AFB culture first. Inform the lab if bedaquiline has been used or is being considered.
Markers & reference ranges
Reference ranges below are typical adult values. Your lab's reported range may differ slightly based on the assay platform and patient demographics — always read your report against the range printed on it.
Cross-resistance: clofazimine and bedaquiline
| Mutation | Effect on clofazimine | Effect on bedaquiline |
|---|---|---|
| Rv0678 (mmpR5) | Reduced susceptibility | Reduced susceptibility |
| atpE | No | High-level resistance |
| pepQ | Reduced | Reduced |
Frequently asked questions
Why is clofazimine important in TB?
It is a key oral companion drug in modern MDR-TB regimens, including BPaLM. Confirming susceptibility protects the regimen and the value of bedaquiline.
If clofazimine is resistant, is bedaquiline also at risk?
Yes — Rv0678 mutations confer reduced susceptibility to both. Bedaquiline DST should be ordered when clofazimine resistance is found.
What side effects does clofazimine cause?
Reddish-brown skin discoloration (most common, reversible), GI upset, ichthyosis, and rarely QT prolongation. Skin colour change is reversible after stopping the drug.
How long does the test take?
About 1–2 weeks from a positive culture. Total time from sputum collection: 4–6 weeks.
Is this test available under NTEP?
Yes — for eligible MDR-TB patients at NTEP intermediate and national reference labs. Private NABL-accredited labs also offer it.
Can clofazimine be used outside TB?
Originally a leprosy drug, clofazimine is also used in leprosy and in some NTM infections (M. abscessus). In TB, it is increasingly central to all-oral regimens.
What if I cannot tolerate clofazimine?
Your specialist will substitute another companion drug guided by the full DST profile and your tolerability.
Related Tuberculosis / Mycobacterial tests
Tests commonly ordered alongside ANTIBIOGRAM - MTB (CLOFAZIMINE), or that help interpret an unexpected result.
Sources & references
- WHO Consolidated Guidelines on Drug-Resistant TB · accessed 2026-05-30T00:00:00.000Z
- NTEP PMDT Guidelines · accessed 2026-05-30T00:00:00.000Z
- India TB Report 2024 · accessed 2026-05-30T00:00:00.000Z
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