What this test measures
This test determines whether a cultured M. tuberculosis isolate is sensitive or resistant to moxifloxacin at the WHO-defined standard critical concentration (0.25 mg/L on MGIT). Moxifloxacin is a fourth-generation fluoroquinolone that inhibits DNA gyrase and is the keystone of fluoroquinolone-containing TB regimens, including the WHO-endorsed BPaLM regimen.
Resistance is mediated by mutations in the gyrA / gyrB genes. Low-level mutations may retain susceptibility at higher moxifloxacin doses — see the high-dose moxifloxacin DST for that distinction.
Why it matters
Moxifloxacin is the most important fluoroquinolone in modern MDR-TB therapy. Confirming susceptibility before starting BPaLM or longer MDR regimens is essential because fluoroquinolone-resistant TB treated with a fluoroquinolone-based regimen will fail and amplify resistance — converting MDR-TB into pre-XDR or XDR-TB.
India's drug-resistance survey shows rising fluoroquinolone resistance, much of it due to ambulatory antibiotic misuse for upper respiratory infections. Detecting this resistance protects regimens and informs national resistance surveillance.
How to prepare
A positive M. tuberculosis culture (MGIT or LJ) is required. If not available, sputum samples must be collected for AFB culture first.
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.
Fluoroquinolones in TB
| Drug | Generation | Role in TB |
|---|---|---|
| Ofloxacin | Older | Largely replaced |
| Levofloxacin | Modern | Alternative fluoroquinolone in MDR-TB regimens |
| Moxifloxacin (this drug) | Modern (4th gen) | Preferred fluoroquinolone; BPaLM backbone |
| Gatifloxacin | Older | Withdrawn due to hypoglycaemia risk |
Frequently asked questions
Why is moxifloxacin so important in TB?
It is the keystone of fluoroquinolone-containing MDR-TB regimens, particularly the 6-month BPaLM regimen (Bedaquiline + Pretomanid + Linezolid + Moxifloxacin).
If standard moxifloxacin is resistant, can I still use it?
Sometimes — strains with low-level resistance may remain susceptible to high-dose moxifloxacin (800 mg). The high-dose moxifloxacin DST clarifies this.
How does moxifloxacin resistance develop?
Most often from prior fluoroquinolone exposure — either for TB or, more commonly in India, ambulatory use for upper respiratory infections and other minor illnesses. Avoiding unnecessary fluoroquinolone use is critical at population level.
What are the side effects?
QT prolongation (ECG monitoring needed), GI upset, tendon issues (rare), and rarely psychiatric effects.
How long does the test take?
About 1–2 weeks from a positive culture; 4–6 weeks total from sputum collection.
Is the test available under NTEP?
Yes — second-line DST including moxifloxacin is offered at NTEP intermediate and national reference labs. Private testing is also available.
Should I avoid moxifloxacin for other infections if I have TB?
Patients with confirmed MDR-TB receiving moxifloxacin-based therapy should not be given moxifloxacin for unrelated infections. For others, moxifloxacin remains a useful antibiotic when clinically indicated.
Related Tuberculosis / Mycobacterial tests
Tests commonly ordered alongside ANTIBIOGRAM - MTB (MOXIFLOXACIN), 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
Book with Zelnoo
Get your ANTIBIOGRAM - MTB (MOXIFLOXACIN) test done at home — transparent prices, NABL-accredited labs.
Zelnoo lets you compare diagnostic test prices across NABL-accredited labs in Mumbai & Thane, book a free home phlebotomist visit, and receive digital reports in 24–48 hours into a consent-first report vault. No subscriptions, no membership fees — pay only for the test you book.
Book ANTIBIOGRAM - MTB (MOXIFLOXACIN) now