TABLE 3.

Frequency of single-step mutation for 10 strains of S. pneumoniae

Strain	Selecting drug	Initial MIC (μg/ml)	Mutation frequency at drug concn showna
			MIC	2×MIC	4×MIC
1	Trovafloxacin	0.125	1.6 × 10−5	<2.0 × 10−10	<2.0 × 10−10
	Ciprofloxacin	1	1.3 × 10−4	<2.0 × 10−10	<2.0 × 10−10
	Clinafloxacin	0.06	<2.0 × 10−10	<2.0 × 10−10	<2.0 × 10−10
2	Trovafloxacin	0.125	5.0 × 10−4	<1.0 × 10−11	<1.0 × 10−11
	Ciprofloxacin	1	4.8 × 10−4	2.9 × 10−9	<1.0 × 10−11
	Clinafloxacin	0.06	<1.0 × 10−11	<1.0 × 10−11	<1.0 × 10−11
3	Trovafloxacin	0.06	1.0 × 10−5	1.2 × 10−6	<5.2 × 10−10
	Ciprofloxacin	1	1.7 × 10−4	5.4 × 10−6	<5.2 × 10−10
	Clinafloxacin	0.06	<5.2 × 10−10	<5.2 × 10−10	<5.2 × 10−10
4	Trovafloxacin	0.06	1.9 × 10−5	1.2 × 10−7	<2.3 × 10−10
	Ciprofloxacin	1	4.5 × 10−5	3.3 × 10−7	<2.3 × 10−10
	Clinafloxacin	0.06	<2.3 × 10−10	<2.3 × 10−10	<2.3 × 10−10
5	Trovafloxacin	0.06	7.0 × 10−6	1.0 × 10−7	<2.5 × 10−10
	Ciprofloxacin	1	1.5 × 10−5	5.0 × 10−9	<2.5 × 10−10
	Clinafloxacin	0.06	2.0 × 10−9	<2.5 × 10−10	<2.5 × 10−10
6	Trovafloxacin	0.06	1.3 × 10−7	<8.8 × 10−10	<8.8 × 10−10
	Ciprofloxacin	1	3.9 × 10−6	<8.8 × 10−10	<8.8 × 10−10
	Clinafloxacin	0.06	<8.8 × 10−10	<8.8 × 10−10	<8.8 × 10−10
7	Trovafloxacin	0.06	3.6 × 10−9	1.6 × 10−10	<1.1 × 10−11
	Ciprofloxacin	1	6.7 × 10−9	<1.1 × 10−11	<1.1 × 10−11
	Clinafloxacin	0.06	<1.1 × 10−11	<1.1 × 10−11	<1.1 × 10−11
8	Trovafloxacin	0.125	3.5 × 10−6	1.5 × 10−8	<6.7 × 10−10
	Ciprofloxacin	1	1.4 × 10−4	1.7 × 10−7	<6.7 × 10−10
	Clinafloxacin	0.06	<6.7 × 10−10	<6.7 × 10−10	<6.7 × 10−10
9	Trovafloxacin	0.125	3.3 × 10−6	8.3 × 10−8	<3.3 × 10−10
	Ciprofloxacin	4	2.3 × 10−5	2.0 × 10−7	<3.3 × 10−10
	Clinafloxacin	0.125	9.6 × 10−8	<3.3 × 10−10	<3.3 × 10−10
10	Trovafloxacin	2	6.7 × 10−8	1.2 × 10−8	<5.6 × 10−10
	Ciprofloxacin	32	2.4 × 10−7	5.6 × 10−8	<5.6 × 10−10
	Clinafloxacin	0.5	1.1 × 10−8	<5.6 × 10−10	<5.6 × 10−10

^aConcentration shown as multiples of the MIC of agent against parent strain.