Dataset Information

Biological and molecular characteristics of Mycobacterium tuberculosis clinical isolates with low-level resistance to isoniazid in Japan.

ABSTRACT: We reevaluated the BACTEC MGIT 960 antimicrobial susceptibility testing system (MGIT 960 AST) by using 1,112 isolates of Mycobacterium tuberculosis. When the results of MGIT 960 AST were compared with that of the proportion method using Ogawa medium (Ogawa PM), discrepant results were obtained for 30 strains with isoniazid, all resistant by MGIT 960 AST but susceptible by Ogawa PM. For 93% of the strains that produced discrepant results, the MIC was 0.4 or 0.8 microg/ml, showing resistance by the proportion method using Middlebrook agar plates. Furthermore, it was also established by analyses of the katG and inhA genes that strains resistant only by MGIT 960 AST have a low level of isoniazid (INH) resistance, indicating that MGIT 960 AST is a reliable method. Ninety-six strains were resistant to 0.1 microg/ml INH by MGIT 960 AST. When they were divided into three groups, Low-S (susceptible at 0.2 microg/ml), Low-R (resistant at 0.2 microg/ml), and High-R (resistant at 1.0 microg/ml), by Ogawa PM, 43.3% of the Low-S strains had mutations in the promoter region of inhA and no mutations were detected in katG codon 315, while 61.7% of the High-R strains had katG codon 315 mutations or a gross deletion of katG. These results suggest that mutations in inhA are associated with low-level resistance to INH and katG codon 315 mutations are associated with high-level resistance to INH. In addition, the analyses demonstrated some relationship of mutations in the inhA gene with ethionamide resistance for the Low-S strains, but not for the High-R strains.

SUBMITTER: Abe C

PROVIDER: S-EPMC2446907 | biostudies-literature | 2008 Jul

REPOSITORIES: biostudies-literature

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Biological and molecular characteristics of Mycobacterium tuberculosis clinical isolates with low-level resistance to isoniazid in Japan.

Abe Chiyoji C Kobayashi Ikuo I Mitarai Satoshi S Wada Masako M Kawabe Yoshiko Y Takashima Tetsuya T Suzuki Katsuhiro K Sng Li-Hwei LH Wang Suxing S Htay Hla Hla HH Ogata Hideo H

Journal of clinical microbiology 20080528 7

We reevaluated the BACTEC MGIT 960 antimicrobial susceptibility testing system (MGIT 960 AST) by using 1,112 isolates of Mycobacterium tuberculosis. When the results of MGIT 960 AST were compared with that of the proportion method using Ogawa medium (Ogawa PM), discrepant results were obtained for 30 strains with isoniazid, all resistant by MGIT 960 AST but susceptible by Ogawa PM. For 93% of the strains that produced discrepant results, the MIC was 0.4 or 0.8 microg/ml, showing resistance by th ...[more]

PMID: 18508939

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Project description:BACKGROUND: Rapid new diagnostic methods (including Xpert MTB/RIF assay) use rifampicin resistance as a surrogate marker for multidrug resistant tuberculosis. Patients infected with rifampicin susceptible strains are prescribed first line anti-tuberculosis therapy. The roll out of such methods raises a concern that strains with resistance to other first line anti-tuberculosis drugs including isoniazid will be missed and inappropriate treatment given. To evaluate implications of using such methods review of resistance data from high burden settings such as ours is essential. OBJECTIVE: To determine resistance to first line anti-tuberculosis drugs amongst rifampicin susceptible pulmonary Mycobacterium tuberculosis (MTB) isolates from Pakistan. MATERIALS AND METHODS: Data of pulmonary Mycobacterium tuberculosis strains isolated in Aga Khan University Hospital (AKUH) laboratory (2009-2011) was retrospectively analyzed. Antimicrobial susceptibility profile of rifampicin susceptible isolates was evaluated for resistance to isoniazid, pyrazinamide, ethambutol, and streptomycin. RESULTS: Pulmonary specimens submitted to AKUH from 2009 to 2011 yielded 7738 strains of Mycobacterium tuberculosis. These included 54% (n 4183) rifampicin susceptible and 46% (n: 3555) rifampicin resistant strains. Analysis of rifampicin susceptible strains showed resistance to at least one of the first line drugs in 27% (n:1133) of isolates. Overall isoniazid resistance was 15.5% (n: 649), with an isoniazid mono-resistance rate of 4% (n: 174). Combined resistance to isoniazid, pyrazinamide, and ethambutol was noted in 1% (n: 40), while resistance to isoniazid, pyrazinamide, ethambutol, and streptomycin was observed in 1.7% (n: 70) of strains. CONCLUSIONS: Our data suggests that techniques (including Xpert MTB/RIF assay) relying on rifampicin susceptibility as an indicator for initiating first line therapy will not detect patients infected with MTB strains resistant to other first line drugs (including isoniazid). The roll out of these techniques must therefore be accompanied by strict monitoring ensuring early resistance detection to increase chances of improved patient outcomes.

Project description:BACKGROUND:Accurate diagnosis of tuberculosis, especially by using rapid molecular assays, can reduce transmission of drug resistant tuberculosis in communities. However, the frequency of resistance conferring mutations varies with geographic location of Mycobacterium tuberculosis, and this affects the efficiency of rapid molecular assays in detecting resistance. This has created need for characterizing drug resistant isolates from different settings to investigate frequencies of resistance conferring mutations. Here, we describe the prevalence and patterns of rifampicin- and isoniazid- resistance conferring mutations in isolates from Uganda, which could be useful in the management of MDR-TB patients in Uganda and other countries in sub-Saharan Africa. RESULTS:Ninety seven M. tuberculosis isolates were characterized, of which 38 were MDR, seven rifampicin-resistant, 12 isoniazid-mono-resistant, and 40 susceptible to rifampicin and isoniazid. Sequence analysis of the rpoB rifampicin-resistance determining region (rpoB/RRDR) revealed mutations in six codons: 588, 531, 526, 516, 513, and 511, of which Ser531Leu was the most frequent (40%, 18/45). Overall, the three mutations (Ser531Leu, His526Tyr, Asp516Tyr) frequently associated with rifampicin-resistance occurred in 76% of the rifampicin resistant isolates while 18% (8/45) of the rifampicin-resistant isolates lacked mutations in rpoB/RRDR. Furthermore, sequence analysis of katG and inhA gene promoter revealed mainly the Ser315Thr (76%, 38/50) and C(-15)T (8%, 4/50) mutations, respectively. These two mutations combined, which are frequently associated with isoniazid-resistance, occurred in 88% of the isoniazid resistant isolates. However, 20% (10/50) of the isoniazid-resistant isolates lacked mutations both in katG and inhA gene promoter. The sensitivity of sequence analysis of rpoB/RRDR for rifampicin-resistance via detection of high confidence mutations (Ser531Leu, His526Tyr, Asp516Tyr) was 81%, while it was 77% for analysis of katG and inhA gene promoter to detect isoniazid-resistance via detection of high confidence mutations (Ser315Thr, C(-15)T, T(-8)C). Furthermore, considering the circulating TB genotypes in Uganda, the isoniazid-resistance conferring mutations were more frequent in M. tuberculosis lineage 4/sub-lineage Uganda, perhaps explaining why this genotype is weakly associated with MDR-TB. CONCLUSION:Sequence analysis of rpoB/RRDR, katG and inhA gene promoter is useful in detecting rifampicin/isoniazid resistant M. tuberculosis isolates in Uganda however, about ≤20% of the resistant isolates lack known resistance-conferring mutations hence rapid molecular assays may not detect them as resistant.

Dataset Information

Biological and molecular characteristics of Mycobacterium tuberculosis clinical isolates with low-level resistance to isoniazid in Japan.

Publications

Biological and molecular characteristics of Mycobacterium tuberculosis clinical isolates with low-level resistance to isoniazid in Japan.

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