TABLE 2.

Colony counts of M. tuberculosis clinical isolates after exposure to INH in 12B medium^a

Isolate and INH concn (μg/ml)	Inoculum (CFU/vial)b	Colony count (CFU) at wk:
		1	2	3	4
TB 7
0.1	2.4 × 104	1.7 × 105	7.6 × 103	2.5 × 104	7.9 × 104
0.4	2.4 × 104	0	5.6 × 102	1.2 × 104	1.1 × 105
TB 19
0.1	1.4 × 105	25	1.1 × 103	4.8 × 103	7.0 × 103
0.4	1.4 × 105	0	2.0 × 102	3.4 × 104	4.8 × 104
TB 20
0.1	2.2 × 105	2.4 × 102	1.4 × 104	1.6 × 104	2.5 × 104
0.4	2.2 × 105	40	1.3 × 104	7.5 × 104	8.0 × 104

^aThree clinical strains of M. tuberculosis were inoculated into vials containing 0.1 or 0.4 μg/ml INH and incubated at 37°C for 4 weeks. Colony counts were measured once a week by taking aliquots from each vial and plating on solid media without antibiotic.

^bTotal CFU inoculated into each drug vial containing 4 ml of 12B medium. The counts/ml of medium will be one-fourth of this.