TABLE 1.

Comparison of MIC of antimycobacterial agents as determined by BDT and SFA

ReagentsMIC (μg/ml)MIC of SFA/ MIC of BDT
BDTaSFAb
Antibiotics
    INH0.1070.4284
    STR0.2271.8168
    RIF0.0260.0131/2
    EMB1.7333.4652
    PZA1,231 (pH 6.6)c>123.1
492 (pH 5.8)d3.8471/128
Other agent
    SA40.6320.321/2
  • a MIC was obtained by the BDT by using Middlebrook 7H9 medium supplemented with 0.05% Tween 80 and 10% ADC. MIC determined by the BDT is defined as the lowest concentration of agents that inhibited visible growth of the bacteria. The partial reduction in turbidity was scored as negative.

  • b MIC was obtained by SFA. MIC determined by SFA is defined as the minimal dose of drugs exhibiting a statistically significant inhibitory effect on the bacterial cytotoxicity as examined by fibroblast viability. The values demonstrate statistically significant inhibition (P < 0.01) of the mycobacterial cytotoxicity. These assay procedures are described in Materials and Methods. The values are means from six wells.

  • c M. tuberculosis H37Rv bacilli were cultured in 7H9 broth at pH 6.6.

  • d The bacilli were cultured in 7H9 broth at pH 5.8.

  • e MRC-5 cells were cultured with bacilli in the presence of PZA for 3 days.

  • f MRC-5 cells were infected with bacilli for 12 h at an MOI of 50:1. The culture medium was replaced by fresh medium without bacilli, and then the cells were cultured with PZA for 2 days.