Table 2. Concentration- and time-dependent bactericidal effect of rifampin toward Mycobacterium tuberculosis genotypes in low- and high-density cultures*.

Day	Lowest RIF concentration resulting in killing of M. tuberculosis, mg/L
	Beijing-1585 genotype						EAI-1627 genotype
	>99% killing			100% killing			>99% killing			100% killing
	Low†	High‡		Low†	High‡		Low§	High¶		Low§	High¶
1	8	ND		256	ND		8	ND		32	ND
3	1	0.008		64	1024		0.125	0.03		8	32
6	0.001	0.008		2	64		0.001	0.06		1	2

*Cultures were exposed to RIF at 2-fold increasing concentrations for 6 days at 37°C; at indicated time-points, subcultures were performed on solid media for counting. Low, low-density culture; high, high-density culture; ND, not determined.
†Density of 5.1 × 10⁵ CFU/mL.
‡Density of 4.4 × 10⁶ CFU/mL.
§Density of 6.8 × 10⁵ CFU/mL.
¶Density of 3.0 × 10⁶ CFU/mL.