P W Ei1, W W Aung2, W W Nyunt3, T L Swe3, M M Htwe2, S M Win2, S T Aung3, C L Chang4, H-Y Lee5, J S Lee6. 1. Advanced Molecular Research Centre, Department of Medical Research, Yangon, Myanmar, Department of Biomedical Laboratory Science, Collage of Health Sciences, Yonsei University, Wonju, Republic of Korea. 2. Advanced Molecular Research Centre, Department of Medical Research, Yangon, Myanmar. 3. National Tuberculosis Programme, Department of Public Health, Naypyidaw, Myanmar. 4. Pusan National University Yangsan Hospital, Yangsan. 5. Department of Biomedical Laboratory Science, Collage of Health Sciences, Yonsei University, Wonju, Republic of Korea. 6. International Tuberculosis Research Center, Changwon, Republic of Korea.
Abstract
SETTING: Two tuberculosis (TB) reference laboratories in Myanmar. OBJECTIVES: To determine the proportion of extensively drug-resistant TB (XDR-TB) cases among multidrug-resistant TB (MDR-TB) cases and the mutations that cause resistance to second-line drugs in Myanmar. DESIGN: This was a cross-sectional, retrospective study. Multidrug-resistant Mycobacterium tuberculosis isolates were collected during 2015-2016. Phenotypic drug susceptibility testing (DST) was performed and drug-resistant mutations identified by sequencing. Genotypes were determined to explain relationships between drug resistance patterns and genotypes. RESULTS: Of 89 MDR-TB isolates, 12 were XDR-TB and 24 were pre-XDR-TB, with 21 resistant to fluoroquinolones (FQs) and 3 to second-line injectable agents (SLIDs). High rates of cross-resistance among second-line drugs were observed. Correlations between phenotypic and molecular DST against FQs and SLIDs were 91% in both cases. The most frequent mutation in FQ-resistant isolates was D94G (8/21) in gyrA and A1401G (11/15) in rrs in those resistant to SLIDs. The dominant genotype was the Beijing type (76/89). CONCLUSION: There were high proportions of XDR-TB and pre-XDR-TB among MDR-TB cases; cross-resistance among second-line drugs was high, with various types of genetic mutations. These data suggest that resistance to second-line anti-tuberculosis drugs should be monitored intensively, and molecular DST should be employed.
SETTING: Two tuberculosis (TB) reference laboratories in Myanmar. OBJECTIVES: To determine the proportion of extensively drug-resistant TB (XDR-TB) cases among multidrug-resistant TB (MDR-TB) cases and the mutations that cause resistance to second-line drugs in Myanmar. DESIGN: This was a cross-sectional, retrospective study. Multidrug-resistant Mycobacterium tuberculosis isolates were collected during 2015-2016. Phenotypic drug susceptibility testing (DST) was performed and drug-resistant mutations identified by sequencing. Genotypes were determined to explain relationships between drug resistance patterns and genotypes. RESULTS: Of 89 MDR-TB isolates, 12 were XDR-TB and 24 were pre-XDR-TB, with 21 resistant to fluoroquinolones (FQs) and 3 to second-line injectable agents (SLIDs). High rates of cross-resistance among second-line drugs were observed. Correlations between phenotypic and molecular DST against FQs and SLIDs were 91% in both cases. The most frequent mutation in FQ-resistant isolates was D94G (8/21) in gyrA and A1401G (11/15) in rrs in those resistant to SLIDs. The dominant genotype was the Beijing type (76/89). CONCLUSION: There were high proportions of XDR-TB and pre-XDR-TB among MDR-TB cases; cross-resistance among second-line drugs was high, with various types of genetic mutations. These data suggest that resistance to second-line anti-tuberculosis drugs should be monitored intensively, and molecular DST should be employed.