TABLE 5.
Analysis of false susceptibility (very major error) and false resistance (major error) results at various drug concentrations (phase III)
| Drug | Inhibitory concn (μg/ml)
|
No. of isolates tested by BACTEC 460 and Middlebrook 7H10 methodsa that were:
|
Errors (%)
|
|||||
|---|---|---|---|---|---|---|---|---|
| In BACTEC 460 medium | On Middlebrook 7H10 agar | S by both tests | R by both testsb | S by BACTEC 460 and R by Middlebrook 7H10 | R by BACTEC 460 and S by Middlebrook 7H10 | VMc (false S) | Md (false R) | |
| Capreomycin | 1.25 | 10.0 | 210 | 15 | 4 | 13 | 21.1 | 6.2h |
| 2.5 | 221 | 11 | 8 | 2 | 42.1 | 0.9 | ||
| 5.0 | 223 | 7 | 12 | 0 | 63.2 | None | ||
| Cycloserinee | 75.0 | 30.0 | 175 | 5 | 14 | 15 | 73.7 | 8.6 |
| 100 | 187 | 2 | 17f | 3 | 89.5 | 1.6 | ||
| 200 | 190 | 0 | 19 | 0 | 100 | None | ||
| Ethionamide | 0.625 | 5.0 | 149 | 56 | 0 | 37 | None | 24.8 |
| 1.25 | 177 | 49 | 7 | 9 | 12.5 | 5.1h | ||
| 2.5 | 182 | 41 | 15 | 4 | 26.8 | 2.2 | ||
| Kanamycin | 2.5 | 5.0 | 206 | 34 | 0 | 2 | None | 1.0 |
| 5.0 | 208 | 34 | 0 | 0 | None | Noneh | ||
| Amikacin | 0.5 | 4.0 | 209 | 32 | 0 | 1 | None | 0.5 |
| 1.0 | 210 | 32 | 0 | 0 | None | Noneh | ||
| Clofazimine | 0.125 | 0.5 | 202 | 3 | 2 | 35 | 40.0 | 17.3 |
| 0.25 | 227 | 2 | 3 | 10 | 60.0 | 4.4 | ||
| 0.5 | 234 | 0 | 5 | 3 | 98.7 | 1.3 | ||
| 0.125 | 1.0 | 204 | 0 | 0 | 38 | NAg | 18.6 | |
| 0.25 | 230 | 0 | 0 | 12 | NA | 5.2 | ||
| 0.5 | 239 | 0 | 0 | 3 | NA | 1.3h | ||
| Ofloxacin | 1.0 | 1.0 | 211 | 21 | 4 | 6 | 16.0 | 2.8 |
| 2.0 | 217 | 20 | 5 | 0 | 20.0 | None | ||
| 4.0 | 217 | 18 | 7 | 0 | 28.0 | None | ||
| 1.0 | 2.0 | 215 | 20 | 0 | 7 | None | 3.3 | |
| 2.0 | 222 | 20 | 0 | 0 | None | Noneh | ||
| 4.0 | 222 | 18 | 2 | 0 | 10.0 | None | ||
| 1.0 | 4.0 | 215 | 18 | 0 | 9 | None | 4.2 | |
| 2.0 | 222 | 18 | 0 | 2 | None | 0.9 | ||
| 4.0 | 223 | 17 | 1 | 1 | 5.6 | 0.5 | ||
| Rifabutin | 0.5 | 1.0 | 158 | 83 | 0 | 1 | None | 0.6h |
| 1.0 | 158 | 82 | 1 | 1 | 1.2 | 0.6 | ||
| 0.5 | 2.0 | 158 | 81 | 0 | 3 | None | 1.9 | |
| 1.0 | 159 | 81 | 0 | 2 | None | 1.3 | ||
S, susceptible; R, resistant.
Reliability of the analyses was questionable due to the very low number of resistant isolates.
VM, very major disagreement (susceptible by BACTEC 460 and resistant by the proportion method).
M, major disagreement (resistant by BACTEC 460 and susceptible by the proportion method).
Site 6 was excluded. For cycloserine no recommendation concerning the critical concentration is being made.
Fourteen of 17 isolates that were resistant by the Middlebrook 7H10 method but susceptible by the BACTEC 460 method were from a single laboratory (site 3).
NA, not applicable since none of the tested organisms were resistant at the conventional concentration.
Critical concentration.