What this test measures
This test determines whether a cultured M. tuberculosis isolate is sensitive or resistant to ofloxacin at the WHO-defined critical concentration. Ofloxacin is an older second-generation fluoroquinolone that has largely been replaced by levofloxacin and moxifloxacin in modern MDR-TB regimens but is still tested for surveillance purposes and as a marker of fluoroquinolone class resistance.
Why it matters
Ofloxacin resistance usually predicts (but does not always equal) resistance to levofloxacin and moxifloxacin, the fluoroquinolones used today. Detecting ofloxacin resistance is therefore an early warning of fluoroquinolone-class problems and a flag to test the newer fluoroquinolones separately.
For India's NTEP, ofloxacin DST is part of routine resistance surveys, even though ofloxacin is rarely used clinically now. It helps national programmes track the spread of fluoroquinolone resistance — a worrying trend given India's widespread ambulatory fluoroquinolone use.
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.
Fluoroquinolone preference today
| Drug | Status | Use case |
|---|---|---|
| Ofloxacin | Largely replaced | Surveillance, salvage only |
| Levofloxacin | Modern | Companion drug in longer MDR regimens |
| Moxifloxacin | Modern (preferred) | BPaLM regimen backbone |
Frequently asked questions
Why is ofloxacin still tested?
It is a sensitive marker of fluoroquinolone class resistance — useful for surveillance and as an early warning that levofloxacin and moxifloxacin may also be compromised.
If I am ofloxacin-resistant, will moxifloxacin work?
Often no, but not always. Cross-resistance is common but not absolute. Order moxifloxacin DST (standard and high-dose) to confirm.
Is ofloxacin used in modern TB regimens?
Rarely — levofloxacin and moxifloxacin have replaced it. Ofloxacin is reserved for surveillance or salvage scenarios.
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 — for surveillance and selected clinical cases at NTEP intermediate and national reference labs.
Why is fluoroquinolone resistance increasing in India?
Widespread ambulatory use of fluoroquinolones (especially ciprofloxacin and levofloxacin) for upper respiratory and abdominal complaints has driven resistance in M. tuberculosis circulating in the community.
What can I do to help?
Avoid taking fluoroquinolones unnecessarily, particularly without a clear prescription. This is one of the most actionable individual contributions to slowing fluoroquinolone resistance.
Related Tuberculosis / Mycobacterial tests
Tests commonly ordered alongside ANTIBIOGRAM - MTB (OFLOXACIN), 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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