GENOTYPIC CHARACTERISTICS IN RPOB AND KATG OF RIF-AND/OR INH-RESISTANT MYCOBACTERIUM TUBERCULOSIS ISOLATES IN CENTRAL VIETNAM

Tuberculosis (TB) is a health burden over the world and one of the most challenges in TB treatment is drug-resistance tuberculosis (DR-TB). Therefore, developing methodologies for TB and DR-TB diagnosis is at the central of TB’s management strategy. This study aimed to evaluate the frequency of DR-TB to Rifampicin and Isoniazid- the two important first-line drugs in TB treatment. Resazurin microtiter assay plate (REMA) - a culture-based phenotypic drug susceptibility testing (DST) was applied in this task. Then we designed a PCR TaqMan probes panel to identifying the DR-TB- associated mutations in rpoB and katG in cultured TB strains from patient’s samples and clinical specimens. In this study, a total of 468 M. tuberculosis isolates were subjected by REMA, 106/468 (22.6%) was resistant isolates; it was observed that of these, 69% (74 strains) were resistant to INH, while 0.94% (1 strain) was resistant to RIF and 29.24% (31 strains) were resistant to both antibiotics (MDR-TB strains). Real-time PCR TaqMan allelic discrimination assay was performed to detect the mutations in rpoB and katG of 52 M. tuberculosis clinical isolates and 52 M. tuberculosis clinical samples using three probes labelled with fluorophores. A total of 19/41(46.34%) of the phenotypic INH resistant isolates had the mutation at codon Ser315Thr (AGCACC). Eight different mutations were detected in the rifampicin resistance determining region (RRDR) of rpoB which were found in 67.7% (22/32) resistance isolates to Rifampicin. The mutations at codons 531, 526 and 516 were 37.5% (12/32), 18.75% (6/32) and 6.25% (2/32), respectively. Susceptible isolates had no mutations in katG and rpoB. With the high sensitivity and specificity, these methods assist rapidly diagnosis, reduce the morbidity and mortality of TB and DR-TB in Vietnam Key word: Mycobacterium tuberculosis, rpoB and katG, Real time PCR TaqMan, genotypic characteristics, REMA.

Tuberculosis (TB) is a health burden over the world and one of the most challenges in TB treatment is drug-resistance tuberculosis (DR-TB). Therefore, developing methodologies for TB and DR-TB diagnosis is at the central of TB’s management strategy. This study aimed to evaluate the frequency of DR-TB to Rifampicin and Isoniazid- the two important first-line drugs in TB treatment. Resazurin microtiter assay plate (REMA) - a culture-based phenotypic drug susceptibility testing (DST) was applied in this task. Then we designed a PCR TaqMan probes panel to identifying the DR-TB- associated mutations in rpoB and katG in cultured TB strains from patient’s samples and clinical specimens. In this study, a total of 468 M. tuberculosis isolates were subjected by REMA, 106/468 (22.6%) was resistant isolates; it was observed that of these, 69% (74 strains) were resistant to INH, while 0.94% (1 strain) was resistant to RIF and 29.24% (31 strains) were resistant to both antibiotics (MDR-TB strains). Real-time PCR TaqMan allelic discrimination assay was performed to detect the mutations in rpoB and katG of 52 M. tuberculosis clinical isolates and 52 M. tuberculosis clinical samples using three probes labelled with fluorophores. A total of 19/41(46.34%) of the phenotypic INH resistant isolates had the mutation at codon Ser315Thr (AGC-ACC). Eight different mutations were detected in the rifampicin resistance determining region (RRDR) of rpoB which were found in 67.7% (22/32) resistance isolates to Rifampicin. The mutations at codons 531, 526 and 516 were 37.5% (12/32), 18.75% (6/32) and 6.25% (2/32), respectively. Susceptible isolates had no mutations in katG and rpoB. With the high sensitivity and specificity, these methods assist rapidly diagnosis, reduce the morbidity and mortality of TB and DR-TB in Vietnam. Developing methodologies for DR-TB diagnosis is at the central of TB’s management strategy. The insights that emphasize and thorough understanding of the genotypic DR-TB isolates are assisted in focusing on infection control, prevent new cases