Isoniazid-resistant TB and associated factors in Ethiopia

BACKGROUND Isoniazid-resistant, rifampicin-susceptible Mycobacterium tuberculosis (Hr-TB) is the most common form of drug-resistant TB (DR-TB). We investigated the prevalence of and risk factors for Hr-TB in Ethiopia. METHODS A cross-sectional study was conducted to determine the magnitude of Hr-TB, and to compare characteristics of persons with Hr-TB to those with multidrug-resistant TB (MDR-TB) and INH/RMP-susceptible TB identified during the National Drug Resistance Survey from 2017–2019. RESULTS Among 1927 M. tuberculosis isolates recovered from persons with pulmonary TB, the prevalence of Hr-TB was 4.1% (95% CI 3.2-5.1), whereas the prevalence of MDR-TB was 1.9%. (95% CI 1.3–2.6). Unlike MDR-TB, the occurrence of Hr-TB did not differ significantly between new and previously treated TB cases ( P = 0.67). The prevalence of Hr-TB cases was high in the Amhara (8.0%, 95% CI 4.8–12.5) region and Addis Ababa (7.1%, 95% CI 3.4–13.0). The proportion of Hr-TB increased with age (OR 1.02, 95% CI 1.01–1.04; P = 0.035). Compared to INH/RMP-susceptible TB, Hr-TB was more likely to harbor resistance to ethambutol, streptomycin and pyrazinamide ( P < 0.0001). CONCLUSIONS Hr-TB is the most prevalent type of DR-TB in Ethiopia and varies among regional states. Given the lack of identifiable clinical factors associated with Hr-TB, we recommend screening all bacteriologically confirmed TB cases for INH resistance at baseline.