TABLE 2.
Performance of the Genotype MTBDR assay with rifampin-resistant and -susceptible strains
| Resistance or susceptibility by BACTEC 460TB | No. (%) of specimens
|
||||
|---|---|---|---|---|---|
| Genotype MTBDR
|
rpoB sequencing
|
||||
| Mutation + | Mutation − | Unsuccessful amplification | Mutation + | Mutation − | |
| Rifampin resistant (n = 26)a | 25 (96.2)c | 0 | 1 (3.8)e | 26 (100) | 0 |
| Rifampin susceptible (n = 117)b | 3 (2.6)d | 102 (87.2) | 12 (10.2)f | 3 (2.6) | 114 (97.4) |
All strains were multidrug resistant.
Fifty-one (43.6%) strains were pansusceptible, 33 (28.2%) strains were resistant to a high level (0.4 μg/ml) of isoniazid, and 33 (28.2%) strains were resistant to a low level (0.1 μg/ml) of isoniazid.
Three strains showed a wild-type and mutation probe-positive hybridization pattern together.
These strains showed susceptibility to RIF at concentrations of 2.0 μg/ml (reportable concentration) and resistance at concentrations of 0.5 μg/ml by the BACTEC 460TB system.
Amplification was unsuccessful for one gene (rpoB).
Amplification was unsuccessful for three genes (M. tuberculosis complex-specific 23S rRNA, katG, and rpoB) in one strain, for two genes (M. tuberculosis complex-specific 23S rRNA and rpoB) in seven strains, and for one gene (rpoB) in four strains.