TABLE 1.

MICs of β-lactam antibiotics tested against VIM-1-producing and control E. coli strains

Antibiotic(s)a	MIC (μg/ml) for E. coli strainb:
	V541 wt	26R793 trc (VIM-1 + AmpC)	26R793	DH5α trf (VIM-1 + AmpC)	DH5α (VIM-2)	DH5α (LAT-1)	DH5α
Ampicillin	>256	>256	2	>256	>256	>256	1
Ticarcillin	>256	>256	1	>256	>256	>256	0.5
Ticarcillin + CLA	>256	>256	1	>256	>256	>256	1
Piperacillin	>256	>256	1	>256	128	>256	0.5
Piperacillin + TAZ	>256	>256	0.5	>256	128	64	0.25
Piperacillin + Ro	>256	256	1	256	128	2	0.5
Cefoxitin	>128	>128	2	>128	>128	>128	2
Cefoxitin + Ro	>128	64	2	64	>128	2	2
Cefotaxime	128	>128	0.12	128	32	32	≤0.06
Cefotaxime + Ro	128	128	≤0.06	64	32	≤0.06	≤0.06
Cefazidime	>128	>128	0.12	>128	64	128	0.12
Ceftazidime + Ro	>128	>128	0.12	>128	64	0.5	0.12
Cefepime	64	32	≤0.06	32	2	0.5	≤0.06
Cefepime + Ro	64	32	≤0.06	32	1	≤0.06	≤0.06
Aztreonam	8	4	≤0.06	4	0.25	16	≤0.06
Aztreonam + Ro	0.25	0.12	0.12	0.12	0.25	0.12	≤0.06
Imipenem	8	8	≤0.06	8	2	0.5	≤0.06
Imipenem + Ro	8	8	≤0.06	8	2	≤0.06	≤0.06
Meropenem	2	2	≤0.06	1	1	0.12	≤0.06
Meropenem + Ro	2	2	≤0.06	1	1	≤0.06	≤0.06

^aCLA, clavulanic acid (2 μg/ml); TAZ, tazobactam (4 μg/ml); Ro, Ro 48-1220 (10 μg/ml).

^bwt, wild-type; trc, transconjugant; trf, transformant. The β-lactamas(es) produced by each strain is in parentheses.