TABLE 2.

Results of genetic and phenotypic characterization of quinolone-resistant mutants

E. coli strain	Mutation(s) in QRDR of:		MIC (μg/ml)b		Doubling time (min)	Change in doubling time (%)c	Qsc	ΔQscd (%)	ςe
	gyrA	parC	CIP	CLM
K-12 JM83	—g	—	0.015	16	24	0	1.57	0	0.05
JM83/3.1	S83L	—	1	16	32	33	1.23	22	0
JM83/3.2	D87G	—	0.5	16	32	33	0.92	41	0.05
JM83/3	S83L, D87G	—	2	16	49	104	1.29	18	0.01
WT	—	—	0.015	4	25	0	1.60	0	0.05
MI	S83L	—	0.5	4	26	4	1.37	14	0.02
MIIa	S83L	—	4	8	27	8	1.38	13	0.05
WT-3.2	D87G	—	0.25	8	27	8	1.17	27	0.12
WT-4	—	S80I	0.03	NDh	ND	ND	1.56	2	0.07
WT-3	S83L, D87G	—	1	8	36	44	1.49	6	0.06
MI-4	S83L	S80I	2	ND	ND	ND	1.33	17	0.05
MII-3.2a	D87G	—	2	16	29	16	1.13	29	0.03
MII-3a	S83L, D87G	—	8–16	16	75	200	0.50	32	0.02
WT-3-4M4	S83L, D87G	S80I	32	ND	ND	ND	1.56	3	0.03
WT-3-4M21	S83L, D87G	E84K	32	ND	ND	ND	1.62	−2	0.00
MIIIa	S83L, D87G	S80I	64	32	35	40	1.00	36	0.06
MIVba	S83L, D87G	S80I	256	64	127	408	0.36	77	0.06
R17	S83L, D87G	S80I	256	32	37	48	0.44	72	0.05
205096f	S83L, D87G	E84K	64	32	21	−16	1.47	6	0.06

^aMII and its derivatives carry a mutation reducing CIP accumulation (23). 

^bSusceptibilities were determined as MICs of CIP and chloramphenicol (CLM) by broth microdilution assay. 

^cThe change in the doubling time of a mutant compared to that of its parent (strain WT or JM83) is given. 

^dDifferences in Qsc values were calculated in comparison to the respective isogenic parent (ΔQsc = 0). 

^eς, standard deviation. 

^fThe data determined for isolate 205096 are calculated in relation to those for strain WT (100%). 

^g—, no mutation detected. 

^hND, not determined.