TABLE 1.

MICs of β-lactams for S. marcescens HD and S3 strains and for recombinant E. coli DH10B(pBK-HD) and E. coli DH10B(pBK-S3)

β-Lactam(s)f	MIC (μg/ml)
	S. marcescens HDa	S. marcescens S3b	E. coli DH10B(pBK-HD)c	E. coli DH10B(pBK-S3)d	E. coli DH10B(pBK-TEM-1)e	E. coli DH10B
Amoxicillin	>512	>512	>512	>512	>512	2
Amoxicillin-CLA	256	>512	256	256	512	2
Ticarcillin	>512	32	8	128	>512	1
Ticarcillin-CLA	256	32	8	128	>512	1
Piperacillin	512	16	256	256	64	1
Piperacillin-TZB	32	8	128	128	32	1
Cephalothin	>512	>512	>512	>512	8	4
Cefoxitin	8	16	128	128	2	2
Cefuroxime	128	512	512	128	0.5	0.5
Ceftriaxone	2	0.25	16	8	<0.06	<0.06
Cefotaxime	2	0.25	16	8	<0.06	<0.06
Ceftazidime	64	0.06	512	16	<0.06	<0.06
Aztreonam	0.5	0.06	0.25	0.06	0.06	0.06
Cefepime	32	0.06	512	2	0.06	0.06
Cefpirome	8	0.06	64	2	0.06	0.06
Imipenem	0.06	0.06	0.06	0.06	0.06	0.06

^aS. marcescens isolate HD produced β-lactamases AmpC HD and TEM-1.

^bS. marcescens isolate S3 reference strain produced β-lactamase AmpC S3.

^cThe recombinant E. coli DH10B(pBK-HD) strain produced β-lactamase AmpC HD.

^dThe recombinant E. coli DH10B(pBK-S3) strain produced β-lactamase AmpC S3.

^eThe recombinant E. coli DH10B(pBK-TEM-1) strain produced β-lactamase TEM-1.

^fCLA, clavulanic acid at 2 μg/ml; TZB, tazobactam at 4 μg/ml.