Table 2.

Susceptibility analyses for antibiotics that target various cellular processes

Drug type or target and drug namea	MICb (μg ml−1)
	OG1RF				T1
	WT	ΔireB mutant	ΔireK ΔireB mutant	ΔireK mutant	WT	ΔireB mutant
Cephalosporins
Ceftazidime (BS)	128	1,024	256	4	128	512
Ceftriaxone (BS)	128	2,048	128	4	64	512
Cefuroxime (ES)	64	512	256	4	64	256
Cefadroxil (NS)	64	64	64	32	64	64
Other cell wall
Ampicillin	0.5	1	0.5	0.5	1	1
Vancomycin	2	2	2	1	2	2
Daptomycin	8	32	16	4	4	4
Protein synthesis
Erythromycin	2	1	1	2	0.5	0.5
Chloramphenicol	4	4	4	4	8	8
Kanamycin	128	128	128	128	64	32
DNA replication
Norfloxacin	4	4	4	4	2	4

^aBS, broad spectrum; ES, expanded spectrum; NS, narrow spectrum.

^bMICs are reported as the medians of three independent experiments performed in MHB broth at 37°C for 24 h. The strain designations in the OG1RF genetic lineage are indicated as follows: the wild type (WT) is strain OG1RF, the ΔireB mutant is strain CK164, the ΔireK ΔireB mutant is strain CK167, and the ΔireK mutant is strain CK119. Strain designations in the T1 genetic lineage are indicated as follows: the wild type is strain T1, and the ΔireB mutant is strain JL376.