Table 5.

RFF based on the accumulation of ethidium bromide for the M. tuberculosis strains in the presence of efflux inhibitors.

Strain	RFF of the inhibitors
	Verapamil	Thioridazine	Chlorpromazine
H37Rv	1.69 ± 0.09***	0.82 ± 0.15*	0.81 ± 0.03**
MtbPT1	0.86 ± 0.03**	0.18 ± 0.06*	0.13 ± 0.02*
MtbPT3	1.68 ± 0.24**	0.78 ± 0.02*	0.45 ± 0.02*
MtbPT5	1.17 ± 0.08**	0.24 ± 0.09	0.26 ± 0.06
MtbBR1	1.76 ± 0.21	1.39 ± 0.32	0.88 ± 0.13
MtbPT7	2.17 ± 0.01*	0.98 ± 0.02*	0.67 ± 0.04*
MtbPT11	2.00 ± 0.21**	1.14 ± 0.11*	1.04 ± 0.03**

Ethidium bromide was used at the equilibrium concentration for each strain as follows: 0.25 μg/ml, H37Rv, MtbPT1, MtbPT5, MtbPT7, and MtbPT11; 0.5 μg/ml, MtbPT3; and 1 μg/ml, MtbBR1; the inhibitors were tested at half MIC. The effect of the inhibitors on the accumulation of ethidium bromide was interpreted as follows: RFF values above zero indicated that the cells accumulate more ethidium bromide under the condition used than those of the control (non-treated cells). Values in boldface (above 1) indicated enhanced accumulation of ethidium bromide in the presence of the efflux inhibitors. Each assay was performed in triplicate and the results presented correspond to the average of three independent assays plus standard deviation (±SD). The results were considered significant when

^*P < 0.05; and highly significant when

^**P < 0.01 and

^***P < 0.001.