Characterisation of Mutations in rpoB Gene and Assessment of Risk Factors in Patients with Rifampicin-resistant Tuberculosis: A Cross-sectional Study from Eastern India

Introduction: Tuberculosis (TB) continues to be a significant public health challenge in India, with alarming prevalence rates and unique socio-demographic risk factors. Resistance to Rifampicin (RIF), is caused by mutations in the rpoB gene of the causative agent. It is usually situated in a region at the 507-533 amino acid residues (81 bp) within the rpoB gene, known as the Rifampicin Resistance Determining Region (RRDR). Aim: To assess the prevalence of Rifampicin Resistance (RR) and identify mutations in the RRDR of the rpoB gene. Materials and Methods: This cross-sectional study was conducted at ESIC Medical College, Patna, in collaboration with the NABL-accredited laboratory associated with Tertiary care Hospitals, Patna, Bihar, India from July 2024 to January 2025. A total of 502 clinical samples from suspected cases of TB were analysed by GeneXpert MTB/RIF testing. Deoxyribonucleic Acid (DNA) extraction was done only for the MTB complex with RR followed by automated DNA sequencing. Data obtained from these 68 RR-MTB clinical samples were enrolled in this study. Statistical analysis was performed using Statistical Package for the Social Sciences (SPSS) software with the association of multivariate logistic regression with p-value <0.05. Results: In this study, 46.57% (68/146) of all MTB-positive patients were RR. The highest alteration was at the Ser/Leu substitution at codon 531 present in 45.6% (31/68) isolates, followed by His/Tyr substitution at codon 526 in 25% (17/68), mutation at codon 516 in 16.17% (11/68) isolates and mutations at codon 511 demonstrated in 13.23% (9/68) isolates. Conclusion: Mutations within the RRDR of the rpoB gene, particularly at codons 531 and 526, were identified as the predominant drivers of RR among pulmonary TB patients in Eastern India. The study highlights the importance of integrating rapid molecular diagnostics with socio-demographic risk assessment to enable early detection, guide individualised treatment, and strengthen regional TB control strategies.