HR-TB refers to Isoniazid-resistant Tuberculosis, meaning the Mycobacterium tuberculosis bacteria causing the infection are resistant to the antibiotic isoniazid, but remain susceptible to rifampicin.
Understanding HR-TB:
- Drug Resistance: In HR-TB, the Mycobacterium tuberculosis bacteria have developed resistance to isoniazid, a first-line drug commonly used to treat TB. This resistance makes the infection harder to treat with standard TB regimens.
- Rifampicin Susceptibility: Crucially, in HR-TB, the bacteria remain susceptible to rifampicin, another important first-line drug. This distinguishes it from multidrug-resistant TB (MDR-TB), where the bacteria are resistant to both isoniazid and rifampicin.
- Treatment Implications: Because the bacteria are resistant to isoniazid, HR-TB usually requires a modified treatment regimen that relies on other effective anti-TB drugs.
- Diagnostic Confirmation: The diagnosis of HR-TB requires laboratory confirmation through drug susceptibility testing (DST), which identifies the specific drugs to which the bacteria are resistant. In vitro testing confirms the resistance.
- Longer MDR-TB Regimens: The provided context mentions "Longer MDR-TB regimens" which are used for the treatment of MDR/RR-TB (Multidrug-resistant or Rifampicin-resistant TB). Although these longer regimens are not first-line treatments for HR-TB they can be useful in some circumstances.
In summary, HR-TB signifies a specific drug-resistance profile in Mycobacterium tuberculosis, impacting treatment strategies and requiring careful monitoring.
