Genetic characterization of Mycobacterium tuberculosis complex isolates circulating in Abuja, Nigeria

Objective: Nigeria ranks fourth among the high tuberculosis (TB) burden countries. This study describes the prevalence of drug resistance and the genetic diversity of Mycobacterium tuberculosis in Abuja's Federal Capital Territory.

Materials and methods: Two hundred and seventy-eight consecutive sputum samples were collected from adults with presumptive TB during 2013-2014. DNA was extracted from Löwenstein-Jensen cultures and analyzed for the identification of nontuberculous mycobacteria species, detection of drug resistance with line probe assays, and high-throughput spacer oligonucleotide typing (spoligotyping) using microbead-based hybridization.

Results: Two hundred and two cultures were positive for M. tuberculosis complex, 24 negative, 38 contaminated, and 15 positive for nontuberculous mycobacteria. Five (2.5%) M. tuberculosis complex isolates were resistant to rifampicin (RIF) and isoniazid (multidrug resistant), nine (4.5%) to RIF alone, and 15 (7.4%) to isoniazid alone; two RIF-resistant isolates were also resistant to fluoroquinolones and ethambutol, and one multidrug resistant isolate was also resistant to ethambutol. Among the 180 isolates with spoligotyping results, 164 (91.1%) were classified as lineage 4 (Euro-American), 13 (7.2%) as lineage 5 (West African 1), two (1.1%) as lineage 2 (East Asia), and one (0.6%) as lineage 6 (West African 2). One hundred and fifty-six (86.7%) isolates were grouped in 17 clusters (2-108 isolates/cluster), of which 108 (60.0%) were grouped as L4.6.2/Cameroon (spoligotype international type 61).

Conclusion: The description of drug resistance prevalence and genetic diversity of M. tuberculosis in this study may be useful for improving TB control in Nigeria.