2 research outputs found
Molecular epidemiology and population structure of Mycobacterium tuberculosis complex strains in tuberculosis patients : implications for diagnostic approaches
No full textAbstract: Tuberculosis (TB) is the 2nd most deadly infectious disease, and its implication for health and economy is increasingly recognized in different countries. In this PhD study, we characterized Mycobacterium tuberculosis complex (MTBc) isolates collected from TB patients in Ethiopia and Niger, two countries in East and West Africa that carry a high burden of TB. In addition, we tested the efficiency of current diagnostic practices for differentiation of MTBc lineages (Ls) and exclusion of drug-resistant TB. In Ethiopia, five MTBc lineages (L1\u2013L4 and L7) were identified from newly recruited pulmonary and lymph node TB patients, with predominance of East-African-Indian (L3) and Euro-American (L4) strains, but a lower than expected prevalence of Ethiopia L7 isolates. The genotypes were similarly distributed between pulmonary and lymph node TB, and all lineages were equally isolated on culture medium and recognized as MTBc by the rapid MPT64 assay. Additionally, analysis of rifampicin-/multidrug-resistant (RR/MDR) TB isolates in Northwest Ethiopia showed four MTBc lineages (L1, L3, L4, and L7), with an expected high rate of the most common rpoB_S450L and katG_S315T mutations causing MDR, but a low proportion of gyrA and rrs mutations causing resistance to second-line drugs. Characterization of RR/MDR-TB isolates from Niger revealed the six major MTBc lineages, L1-L6, with a predominance of the L4 \u201cGhana\u201d and \u201cCameroon\u201d families. We noticed a significantly faster conversion to smear-negative microscopy results during treatment and a more likely favorable outcome for patients infected by \u201cCameroon\u201d isolates (log-rank p < 0.01). Other risk factors such as gender, age, HIV status, body mass index, and treatment regimen were not associated with sputum smear- and culture- conversion. As a supplemental study, we incorporated retrospective rapid molecular testing (MTBDRsl) results from the STREAM stage 1 central database to assess its negative predictive value (NPV) directly from sputum samples compared to phenotypic drug-susceptibility testing. We found 9 (2.3%) fluoroquinolones (FQ)- and 5 (1.3%) second-line injectables (SLI)- discordant phenotypic/genotypic drug-susceptibility testing results. The NPV of MTBDRsl for exclusion of FQ resistance was 99.2% and for SLI resistance 100%. In conclusion, our studies provided great insights into the population structure of the MTBc in Ethiopia and Niger, demonstrating that treatment response varied by lineage. Finally, MTBDRsl is suitable for excluding resistance to second-line agents from clinical samples at the start of RR/MDR-TB treatment, including testing of paucibacillary specimens
Strain diversity and gene mutations associated with presumptive multidrug-resistant Mycobacterium tuberculosis complex isolates in Northwest Ethiopia
No full textAbstract: Objectives: 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.Methods: 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.Results: 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. Conclusions: 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.(c) 2022 The Author(s). Published by Elsevier Ltd on behalf of International Society for Antimicrobial Chemotherapy. This is an open access article under the CC BY license ( http://creativecommons.org/licenses/by/4.0/
