TABLE 1.
MICs and MBCs of CPZ and TZ for antibiotic-sensitive and MDR strains of M. tuberculosisa
| Drug | Susceptible strains
|
Resistant strains
|
||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| ATCC 27294
|
A
|
B
|
C
|
D
|
E
|
|||||||
| MIC (μg/ml) | MBC (μg/ml) | MIC (μg/ml) | MBC (μg/ml) | MIC (μg/ml) | MBC (μg/ml) | MIC (μg/ml) | MBC (μg/ml) | MIC (μg/ml) | MBC (μg/ml) | MIC (μg/ml) | MBC (μg/ml) | |
| CPZ | 10 | 20 | 10 | 20 | 10 | 20 | 30 | 40 | 20 | 30 | 20 | 30 |
| TZ | 15 | 30 | 15 | 30 | 15 | 30 | 30 | 50 | 20 | 30 | 20 | 30 |
The individual MICs of RIF, INH, SM, EMB, CPZ and TZ, were determined by the BACTEC 460-TB method, as described previously (1, 8, 36). Stock solutions containing various amounts of each compound were freshly prepared in BACTEC 460 medium, and 0.1-ml aliquots of each solution were added to BACTEC 460 vials. The final concentrations of CPZ and TZ in the BACTEC 460 vials were 0, 1, 5, 10, 15, 20, 30, 40, 50, and 60 mg/liter. A total of 0.1 ml of BACTEC 460 medium containing an adjusted concentration of mycobacteria corresponding to approximately 105 to 106 CFU was added to each vial (36). The MBCs of CPZ and TZ were determined by extending the MIC curves well beyond each MIC, and 10-μl aliquots of the 10-ml cultures at zero time and those after 30 days that showed no evidence of growth in the BACTEC 12B vials were subjected to counting of the numbers of CFU (36). The MIC and MBC determinations were repeated three times, and the values obtained did not differ significantly. Strains ATCC 27294, A, and B are susceptible to INH, RIF, SM, and EMB. Strain C is resistant to all four drugs. Strains D and E, besides being resistant to INH and RIF, are also resistant to SM.