Treatment Outcomes of High- and Low-Level Isoniazid-Resistant Tuberculosis: Analysis from A Nationwide Pulmonary Tuberculosis Cohort

Objectives Isoniazid resistance is the most common first-line drug resistance in tuberculosis (TB) and is associated with poor outcomes when standard therapy is used. Whether different levels of resistance carry distinct prognostic implications remains unclear. Methods We identified patients with pulmonary isoniazid-mono-resistant TB (2008-2017) from the Taiwan Centers for Disease Control database and compared outcomes, including survival and time to culture conversion within, persistent sputum culture positivity at 7-12 months, and time to recurrence and acquired multidrug-resistance (MDR) within 2 years, between the high- and low-level resistance groups. Results Of 145,498 TB patients, 4,596 had isoniazid mono-resistance (high-level: 2,279 [50.4%]; low-level: 2,317 [49.6%]). Patients in the high-level resistance group more frequently received fluoroquinolones (30.9% vs. 23.2%, p Conclusions High-level isoniazid mono-resistance was associated with delayed sputum culture conversion and an increased risk of acquired MDR, underscoring the need for rapid molecular detection.