Molecular mechanisms of multidrug resistance in Mycobacterium tuberculosis in South Korea

Abstract

Background: Tuberculosis (TB) is an infectious disease caused by Mycobacterium tuberculosis (MTB). Multidrug-resistant tuberculosis (MDR-TB) caused by MTB resistant to the first-line anti-TB drugs, rifampicin, and Isoniazid poses a major challenge to treat TB. The World Health Organization (WHO) reported in 2018 that 10 million people developed TB and at the same time, the global burden of MDR-TB was estimated to be 558,000 cases leading to 240,000 deaths. The objective of this study is to gain firm scientific evidence for a diagnostic strategy for MDR-TB reflecting the current situation. This study assessed the molecular mechanism of resistance to rifampicin and Isoniazid for the latest MTB isolates. Method: A total of 54 MTB isolates from pulmonary specimens (n = 42), and other (n = 12) was collected from Gangnam Severance Hospital, South Korea from September 2018 to February 2019. DNA was extracted from liquid culture by boiling method and used for PCR. Partial and katG genes were amplified by using two pairs of gene-specific primers and directly sequenced . The translated nucleotide sequence was aligned by using the Basic Local Alignment Search Tool and the alterations were determined. The results were compared with the susceptibility testing results of the two drugs. Results: One isolate (1.85%) was resistant to both rifampicin and Isoniazid and the other 4 isolates (7.40%) were resistant to only Isoniazid. Aligning the nucleotide sequences obtained from the PCR amplicons of 397-bp rpoB and 727-bp katG is assessed. Among the 54 isolates, only 5 isolates were resistant to rifampicin or Isoniazid or both. Of those, mutation in RpoB was identified in one isolate carried mutation in 508Leu to Gly and 515Ser to Leu. Mutations in KatG were identified in 5 (9.25%) resistant isolates, of which 3 carried a mutation in 335Ile to Ser, Pro, or Leu and 2 remaining carried mutations in 315Ser to Thr. Conclusion: This study shows the importance of new diagnostic methods covering up the news mutations and alterations of amino acid of KatG and RpoB gene in South Korea along with the continued amplifications-based diagnostic for rapid detection of Isoniazid and rifampicin isolates resistance.