Prevalence of non-tuberculous mycobacteria among previously treated TB patients in the Gulf of Guinea, Africa

•Differentiation of non-tuberculous mycobacteria (NTM) from Mycobacterium tuberculosis complex is important for the management of tuberculosis.•hsp65 gene amplification and sequencing provide accurate diagnosis of NTM.•Mycobacterium fortuitum is the most prevalent NTM in the Gulf of Guinea.•NTM is associated with unsuccessful treatment of patients with tuberculosis. Differentiation between non-tuberculous mycobacteria (NTM) and Mycobacterium tuberculosis complex (MTBC) is crucial for case management with the appropriate antimycobacterials. This study was undertaken in three West and Central African countries to understand NTM associated with pulmonary tuberculosis in the sub-region. A collection of 503 isolates (158 from Cameroon, 202 from Nigeria and 143 from Ghana) obtained from solid and liquid cultures were analysed. The isolates were tested for drug susceptibility, and MTBC were confirmed using IS6110. All IS6110-negative isolates were identified by 65-kilodalton heat shock protein (hsp65) gene amplification, DNA sequencing and BLAST analysis. Overall, the prevalence of NTM was 16/503 (3.2%), distributed as 2/202 (1%) in Nigeria, 2/158 (1.3%) in Cameroon and 12/143 (8.4%) in Ghana. The main NTM isolates included 5/16 (31.3%) M. fortuitum, 2/16 (12.5%) M. intracellulare and 2/16 (12.5%) M. engbaekii. Eight (57.1%) of the 14 previously treated patients harboured NTM (odds ratio 0.21, 95% confidence interval 0.06–0.77; P=0.021). Three multi-drug-resistant strains were identified: M. engbaekii, M. fortuitum and M. intracellulare. NTM were mainly found among individuals with unsuccessful treatment. This highlights the need for mycobacterial species differentiation using rapid molecular tools for appropriate case management, as most are resistant to routine first-line antimycobacterials.