Molecular Characterization of Drug-Resistant Mycobacterium tuberculosis Isolated from HIV-Positive Patients in Rivers State, Nigeria
M. A. Alex-Wele *
Department of Medical Microbiology, University of Port Harcourt Teaching Hospital, Port Harcourt, Rivers State, Nigeria.
O. K. Obunge
Department of Medical Microbiology, University of Port Harcourt Teaching Hospital, Port Harcourt, Rivers State, Nigeria.
*Author to whom correspondence should be addressed.
Abstract
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.
Keywords: Mycobacterium tuberculosis, HIV, drug resistance, MDRTB, rifampicin, isonaizid, line probe assay