Distribution and frequency of common mutations in rpoB gene of Mycobacterium tuberculosis detected by Xpert MTB/RIF and identification of residential areas of rifampicin resistant-TB cases: A first retrospective study from Mizoram, Northeast India

Background: Rifampicin resistance (RR) is a surrogate marker of multidrug-resistant tuberculosis. The aim of this study is to determine the frequency of the commonly mutated probes for rpoB gene and locate the residential areas of the Rifampicin Resistant-TB (RR-TB) patients in a high endemic zone of Northeast India.

Methods: Archived data of 13,454 Xpert MTB/RIF reports were evaluated retrospectively between 2014 and 2021. Socio-demographic and available clinical information were reviewed and analyzed for RR-TB cases only. Logistic Regression was used to analyze the parameters with respect to probe types. P-value ≤ 0.05 was considered to be statistically significant.

Results: 2,894 patients had Mycobacterium tuberculosis infection out of which 460 were RR-TB, which was most prevalent among 25-34 years. The most common mutation occurred in probe A (25.9 %) followed by E (23.5 %), D (9.8 %), B (2.6 %) and the least in C (0.2 %). High prevalence (34.3 %) of probe mutation combinations were also found: probes AB (0.4 %), AD (32.8 %), AE (0.4 %), DE (0.2 %) and ADE (0.4 %). Seventeen patients (3.7 %) were found without any missing probes. RR-TB patients were mostly located in Aizawl North -III, South -II and East -II constituencies.

Conclusion: This study provides genetic pattern of drug resistance accountable for RR over the past years in Mizoram which will help local clinicians in the initiation of correct treatment. Also, our findings provide a baseline data on the magnitude of RR-TB within the state and identification of the residential areas can help local health authorities in planning surveillance programs to control the spread of RR-TB.