Table 3.

Characterization of MTB72-derived isoniazid-resistant mutants initially selected with 0.4 mg/L isoniazid

Acquired MIC	Mutation frequency	No. of ΔkatG (%)	No. of targeted mutations (%)
Undefined	8.02 × 10−6	8/29 (28%)	0/29 (<3.5%)
0.4 < MIC < 2.0	—	3/30 (10%)	0/30 (<3.3%)
MIC > 2.0a	—	—	0/120 (<0.8%)

A subdivision of two groups of mutants was made on the basis of their acquired isoniazid MIC, indicated in the column ‘acquired MIC’. MIC is expressed in terms of mg/L isoniazid. Mutation frequency is the proportion of mutants. No. of ΔkatG is the number of katG deletion mutants. No. of targeted mutations is the number of katG-S315T or inhA-C(-)15T found in the characterized mutants.

^aDNA samples were derived from mutants pooled in sets of four.