TABLE 4.

Resistance profiles of site-directed mutagenesis-constructed E. coli AcrB mutants and wild-type acrB-overexpressing 3-AG100 reference strain

Strain	MIC (μg/ml)a
	LZD	CHL	CXM	OXA	CLI	TET	TGC	LVX	NOV	RIF	CLR	ERYb	AZM
ΔAcrB mutant (derived from 3-AG100)	16	1	0.25	0.5	4	0.5	0.06	0.06	2	8	4	16	2
Plasmid-based acrB strains
ΔAcrB × pAcrBwt strain	256	2	2	64	256	2	0.25	0.25	32	8	64	512	32
ΔAcrB × pAcrB-I38F strain	32	1	0.25	16	32	0.5	0.13	0.13	32	8	128	512	32
ΔAcrB × pAcrB-I671T strain	32	1	0.25	16	32	0.5	0.13	0.13	32	8	256	512	32
Chromosome-based acrB mutants and parental strain
3-AG100 (parental reference strain)	1,024	16	16	512	512	4	0.5	2	1,024	16	256	>1,024	256
I671T ΔAcrB mutant	16	2	0.25	0.5	4	0.5	0.13	0.06	2	8	4	8	2
Constructed I38F I671T mutant	16	1	0.25	8	16	0.5	0.13	0.06	256	16	512	256	32

^aLZD, linezolid; CHL, chloramphenicol; CXM, cefuroxime; OXA, oxacillin; CLI, clindamycin; TET, tetracycline; TGC, tigecycline; LVX, levofloxacin; NOV, novobiocin; RIF, rifampin; CLR, clarithromycin; ERY, erythromycin; AZM, azithromycin. MIC changes of ≥4-fold detected from plasmid-based and chromosome-based AcrB mutants with point mutations compared to the ΔAcrB × pAcrB_wt and 3-AG100 wild-type AcrB-expressing strains, respectively, are depicted in boldface.

^bThe limit of ERY solubility in broth is 1,024 μg/ml.