11.1 Introduction

Rifampicin-susceptible and isoniazid-resistant tuberculosis (Hr-TB) treatment is indicated in children and adults with pulmonary TB (PTB) and extrapulmonary TB (EPTB) when:   

• Susceptibility to rifampicin is confirmed by drug susceptibility testing (DST) and resistance to isoniazid is confirmed by DST, 

or  

• Susceptibility to rifampicin is confirmed by DST and resistance to isoniazid is strongly suspected (i.e. household or close contacts of a patient with confirmed Hr-TB), while waiting for DST results for isoniazid, or if susceptibility to isoniazid cannot be tested. 

Patient with Hr-TB should be treated with the standard Hr-TB regimen [1] Citation 1. Fregonese F et al. Comparison of different treatments for isoniazid-resistant tuberculosis: an individual patient data meta-analysis. Lancet Respir Med. 2018 Apr;6(4):265-275. [2] Citation 2. World Health Organization. WHO operational handbook on tuberculosis. Module 4: treatment - drug-resistant tuberculosis treatment, 2022 update. Geneva; 2022.
https://www.who.int/publications/i/item/9789240006997 when:   

• Susceptibility to fluoroquinolones is confirmed 

and, if possible  

• Susceptibility to pyrazinamide is confirmed. 

Notes:  

• Fluoroquinolone resistance can be detected at the same time as isoniazid resistance by a rapid molecular test (Xpert MTB/XDR).  
• Pyrazinamide resistance is detected by more complex tests (phenotypic DST or Genoscholar PZA-TB ll) that cannot always be performed, or for which the results are not available at the start of treatment. 
• Susceptibility to ethambutol cannot be confirmed as there is no reliable DST.   

Other regimens should be considered for patients with additional resistance, contraindication or intolerance to fluoroquinolones and/or pyrazinamide.