FIG. 3.

Measurement of inhibitory effect of PZA on mycobacterial cytotoxicity by modified method of SFA. (a) Coculture with bacilli and PZA. MRC-5 cells were cultured without (○) or with (•) M. tuberculosis H₃₇Rv bacilli at an MOI of 50:1 in the presence of PZA at the indicated concentrations for 3 days. (b) Culture with PZA after infection. MRC-5 cells were precultured without (○) or with (•) M. tuberculosis H₃₇Rv bacilli at an MOI of 50:1 for 12 h, and then the cells were washed to remove bacilli remaining in the culture medium. Then, the cells were cultured for 3 days in the presence of PZA at the indicated concentrations. The results are the means ± SD of six wells. Experiments were carried out more than three times, and representative data are shown. Data were analyzed by t test compared with control cells containing no bacteria and no PZA. ∗, statistical significance (P < 0.01) versus the cells without bacteria.