TABLE 2.

Emergence of resistance to ciprofloxacin in the presence of NorA inhibitors

Inhibitor (concn [μg/ml])	Frequency of emergence of resistancea
	Spontaneous	Mutagenized
None	2 × 10−8	1 × 10−7
Reserpine (20)	<1 × 10−10	<2.5 × 10−10
INF 55 (5)	<1 × 10−10	<2.5 × 10−10
INF 240 (5)	2 × 10−10	2.5 × 10−10
INF 271 (5)	<1 × 10−10	<2.5 × 10−10
INF 277 (5)	<1 × 10−10	<2.5 × 10−10
INF 392 (1)	2 × 10−10	1 × 10−9

^aFrequency of emergence of in vitro-selected variants of SA1199 resistant to 1 μg of ciprofloxacin per ml (two times the MIC for strain SA1199) in either the absence or the presence of NorA inhibitors. The results of one of three experiments is presented.