Monitoring of Mutations Associated with Drug Resistance of Mycobacterium tuberculosis

The objective: to determine the types and prevalence of Mycobacterium tuberculosis DNA mutations associated with resistance to rifampicin, isoniazid, ethambutol, fluoroquinolones and injectable drugs in MDR TB patients in Arkhangelsk Oblast. Subjects and Methods. In Arkhangelsk Oblast, all patients underwent examination by molecular genetic testing and phenotypic methods for drug susceptibility. In 2010-2017 in Arkhangelsk Oblast, 1064 new MDR TB cases were registered. A total of 1340 cases of MDR TB were registered during this period, including 276 cases with recurrent MDR. Mutations associated with resistance to rifampicin ( rpoB gene) and isoniazid ( inhA, katG genes) were identified by Genоtype MTBDR plus (Hain Lifescince); mutations associated with resistance to fluoroquinolones ( gyrA gene), injectable drugs ( rrs gene) and ethambutol ( emB gene) were identified using GenoType MTBDR sl (Hain Lifescince) in accordance with the manufacturer's recommendations. Results. In 2010–2017 among 1064 new MDR TB cases, Mycobacterium tuberculosis mutations associated with simultaneous resistance to rifampicin and isoniazid were detected in 922/1064 (87%) cases; mutations associated with monoresistance to isoniazid were found in 2/1064 people. 1196/1340 (89%) MDR TB cases underwent examination with GenoTуре MTBDRsl. The predominant mutation in the rpoB gene was the S531L mutation (86.6%), the second and third most frequent mutations were D516V (5.3%) and L511P (2.6%), respectively. Mutations in codon 526 were less frequent than the others. In all MDR TB cases, mutations in the katG gene were detected, which were combined with mutations in the inhA gene in 85 (9.2%) cases. Only two cases had isolated mutations in the inhA gene. The predominant mutation among M. tuberculosis isolates associated with resistance to isoniazid was S315T1 (98.8%) in the katG gene, and C15T in the inhA gene. According to the results of our study, mutations in the gyrA gene were present in 13.6% (163/1196; 95% CI 11.7–15.7%) of cases, in the embB gene – in 49.7% (594/1196; 95% CI 46.8–52.5%), in the rrs gene – in 7.1% (85/1196; CI 95% 5.7–8.7%). Among all studied isolates with resistance to fluoroquinolones, the most common mutation in the gyrA gene was D94G (79/163; 48.5%), including cases without wild-type dropout. The A90V mutation was present in 19% of cases. The S91P mutation was detected in 11.7% of isolates. The D94N and D94A mutations occurred in 9.2% and 7.4% of cases, respectively. In 3 cases, two mutations were present simultaneously. All isolates in our study had mutations in the rrs gene associated with high levels of resistance to injectable drugs (A1401G and G1484T). In the rrs gene, the rrs A1401G mutation was most common (81/85; 95.3%), including cases of simultaneous detection of “mutant samples” and “wild type” samples. In 4.7% of cases, the G1484T mutation was detected. In Arkhangelsk Oblast, 81.5% (95% CI 78.1% to 84.5%) of mutations in the embB gene were M306V mutations and 18.5% (95% CI 15.5% to 21.9%) were M306I mutations.