Molecular Characterization of Drug-Resistant Mycobacterium tuberculosis Isolated from HIV-Positive Patients in Rivers State, Nigeria

Background: Drug resistant tuberculosis is a major challenge in the global bid to control the disease burden and improve treatment outcomes of DRTB infected individuals.

Aim: To determine the molecular characteristics and pattern of drug resistance to first line anti-tuberculosis drugs in HIV sero-positive patients in River State using line probe assay.

Methods: The Line Probe Assay (LPA) was used to assess the drug resistance pattern and gene mutations in 260 sputum specimens collected consecutively from 260 adult, HIV sero-positive subjects presenting with symptoms suggestive of TB in clinical settings across Rivers State, Nigeria.

Results: The results showed a 61.2% (n = 159) prevalence of TB among all study subjects. LPA analysis showed that 16 (10.1%) were multidrug resistant strains, 17 (10.7%) Rifampicin (RIF) monoresistant strains, 24 (15.1%) Isonaizid (INH) monoresistant strains and 102 (64.2%) drug susceptible strains. Among all 33 RIF-resistant strains, 24 (75%) had a mutation in rpoB S531L at the MUT3 band. Another mutation was observed at rpoB H526D (1/17) in RIF-monoresistant strains but not in MDR-TB strains. In INH resistant strains, mutations were observed at the katG gene [32/39 (82.1%)] which constituted 13/15 (86.7%) in MDR-TB strains and 19/24 (79.2%) in INH-monoresistant strains (p =0.002). Overall frequency of inhA mutation was 6/39 (15.4%); MDR-TB strains [2/15 (13.3%)] and INH-monoresistant strains [4/24 (16.7%), p = 0.2]. Combined KatG and inhA mutation was found in 1/39 (2.6%) of INH-monoresistant strains and in none of MDR-TB strains. Of the single inhA mutation bands, only 1/39 (4.2%) MUT 3B (T8A mutation) was observed in INH-monoresistant strains.

Conclusion: The results showed that drug-resistant TB is prevalent in Rivers State with various gene mutations observed in the different TB strains isolated, making LPA analysis a necessity in the bid to improving prevention and control efforts in the region.