The presence of a mutation described as conferring resistance to RMP thus took precedence over the treatment outcome, since it is known that patients may fail or relapse from treatment due to other reasons than (RMP) drug resistance, while conversely, a low proportion of TB patients seem to be cured spontaneously, independent of drug resistance (, ). Table shows details of the panel strains. Of the 14 strains with rpoB mutations, 6 (R1 to R6) were classified as resistant to RMP (mutation plus treatment failure) and 8 (PR1 to PR8) as probably resistant, 5 of which were isolated from relapse cases after category 2 treatment. The mutations identified from the panel strains were Asp516Tyr ( n = 4), Leu511Pro ( n = 3), Leu533Pro ( n = 2), His526Leu, His526Ser, Ser531Leu, and Ile572Phe ( n = 1 each), by the Escherichia coli codon numbering system. One strain had the double mutation Met515Ile and Asp516Tyr. Ten clones of this strain were tested and showed identical nucleotide changes, thus ruling out a possible mixture of strains.

None of the rpoB sequencing patterns showed simultaneously a wild type and a mutation peak, also suggesting the absence of strain mixtures. Three strains (PS1 to PS3) were considered probably susceptible to RMP (no mutation but category 2 treatment failure or relapse). The two strains called susceptible (S1 and S2) showed a wild-type rpoB sequence without any clinical suspicion of RMP resistance. Most R, PR, and PS strains were resistant to one or more of the other first-line TB drugs. All strains except two originated from long-term monitoring of drug resistance among retreatment cases in Bangladesh. This panel was sent to nine volunteer SRLs for blinded RMP DST. Each SRL used its standard RMP susceptibility-testing method(s), based on the original publication of the proportion method (performed on LJ medium or Middlebrook 7H10 agar) or on the manufacturer's instructions (Bactec 460 TB radiometric and Bactec 960 MGIT) ().

Dynex Usb Microphone Driver Download. Six of the participating SRLs performed DST using the LJ proportion method, two reported results by the Middlebrook 7H10 agar proportion method, and two by Bactec 460 radiometric and two by Bactec 960 MGIT DST. Three SRLs reported results with the proportion method, as well as one of the Bactec methods, and some reported incomplete sets of results.

To provide more detailed information, the MIC was determined by each method, using RMP at 10, 20, 30, 40, and 80 μg/ml in LJ medium or at 0.25, 0.5, 1, 2, and 4 μg/ml in agar and Bactec medium, but maintaining the interpretation criteria recommended for each method. The ratio of the MICs to the standard critical concentration for the medium used (40 μg/ml for LJ medium, 2 μg/ml for radiometric Bactec medium, and 1 μg/ml for agar and MGIT) was calculated to allow comparison of MICs obtained with the different methods used. MICs out of the range of RMP concentrations tested were arbitrarily assigned a value corresponding to the next higher or lower dilution. A MIC/critical concentration ratio of >1 was interpreted as resistant.