Strain diversity and gene mutations associated with presumptive multidrug-resistant Mycobacterium tuberculosis...

In this study, we assessed the genetic diversity and gene mutations that confer resistance to rifampicin (RIF), isoniazid (INH), fluoroquinolone (FQ), and second-line injectable (SLI) drugs in RIF-resistant (RR)/multidrug-resistant tuberculosis (MDR-TB) isolates in Northwest Ethiopia.

Spoligotyping was used to assign isolates to TB lineages (Ls), and Hain line probe assays were used to detect resistance to RIF, INH, and FQs, and SLIs.

Among 130 analyzed strains, 68.5% were RR, and four major Mycobacterium tuberculosis complex lineages (L1, L3, L4, and L7) were identified with a predominance of the Euro-American L4 (72, 54.7%), while L7 genotypes were less common (3, 2.3%). Overall, the L4-T3-ETH (41, 32.0%), L3-CAS1-Delhi (29, 22.7%), and L3-CAS1-Killi (19, 14.8%) families were most common. Line probe analysis showed that among rpoB mutants, 65.2% were S450L, while 87.8% of katG mutants were S315T. Only three isolates showed mutation (c-15t) at the inhA gene, and no double mutation with katG and inhA genes was found. Six strains, two each of L1, L3, and L4, were resistant to FQs, having gyrA mutations (D94G, S91P), of which three isolates had additional resistance to SLI (rrs A1401G or C1402T mutations) including one isolate with low-level kanamycin (KAN) resistance.

This study showed a predominance of L4-T3-ETH, L3-CAS1-Delhi, and L3-CAS1-Killi families, with a high rate of rpoB_S450L and katG_S315T mutations and a low proportion of gyrA and rrs mutations. L7 was less frequently observed in this study. Further investigations are, therefore, needed to understand L7 and other lineages with undefined mutations.