TABLE 1.

In vitro susceptibility profiles of E. coli DH5α derivatives carrying the cloned bla_IMP-18 genes and E. coli DH5α carrying the empty plasmid^a

β-Lactam	MIC (μg/ml)
	E. coli DH5α (pLBII-IMP-18)	E. coli DH5α (pLBII-IMP-1)	E. coli DH5α (pBC-SK)
Ampicillin	64	256	4
Piperacillin	1	1	1
Ticarcillin	256	512	8
Temocillin	16	32	16
Cephalothin	32	256	4
Cefoxitin	256	>256	4
Cefuroxime	64	128	4
Cefotaxime	32	8	0.25
Ceftazidime	32	32	0.25
Ceftriaxone	4	8	0.25
Cefepime	2	4	0.25
Cefotetan	32	>32	0.25
Imipenem	1	2	0.06
Meropenem	0.06	2	≤0.015
Ertapenem	0.12	2	≤0.015
Aztreonam	0.12	0.12	0.12

^aStrains producing the IMP-1 enzyme or carrying the empty vector are shown for comparison.