Prevalence of genetic pattern in isoniazid-resistant PTB cases and its association with other TB-resistance drugs

Abstract

Introduction: Isoniazid (H) is one of the most important first-line antituberculosis drugs used for the treatment of active tuberculosis (TB) and latent TB infection (LTBI) with high bactericidal activity and a good safety profile. The emergence of TB strains resistant to isoniazid threatens to reduce the effectiveness of TB treatment. Specific INH resistance allele is more frequently associated with resistance to other drugs. Aim and Objectives: To analyze the prevalence of mutations in genes associated with isoniazid resistance and to explore the association of specific mutations conferring other drugs resistance. Material and Methods: This is a prospective study done from October 2018 to July 2020 in the Department of Pulmonary Medicine, Guntur Medical College, Govt. Fever Hospital, Guntur. A total of 369 sputum-positive isoniazid-resistant pulmonary TB cases were included in the study and subjected to line probe assay (LPA). Results: The prevalence of InhA and KatG gene mutation is 63.14% and 36.85%, respectively. InhA gene is associated with fifampicin mutation in 7.72%, fluoroquinolone (FQ) in 6%, and second-line injectables (SLI) in 1.71% cases. KatG gene is associated with rifampicin mutation in 13.23%, FQ in 7.35%, and SLI in 1.47% cases. Conclusion: InhA gene is the most common gene pattern observed in isoniazid-resistant cases and associated equivalently with other drug resistance patterns such as KatG indicating the recent change in the level of resistance of InhA-resistant strains.