TABLE 1.

MIC of and specific enzymatic activity in response to imipenem after induction with increasing concentrations of zeocin

Strain	Genotypea		MIC of imipenem (mg/liter) on Mueller-Hinton agar supplemented with zeocin at the indicated concn (mg/liter)b					Specific activities (mU/mg of protein) using imipenem as the substrate after induction with zeocin at the indicated concn (mg/liter)c
	blaNDM−1	bleMBL	0	10	50	100	500	0	10	50
E. coli TOP10 (pCR2.1)	−	−	0.12	−	−	−	−	ND	ND	ND
E. coli TOP10 (pCR2.1 PNDM-blaNDM-1-bleMBL)	+	+	>32	>32	>32	>32	16	2.92 ± 0.26	3.07 ± 0.14ns	2.84 ± 0.21ns
E. coli 271	+	+	6	6	6	4	2	4.67 ± 1.33	7.17 ± 1.15ns	5.24 ± 0.65ns
K. pneumoniae 419	+	+	1.5	1	1	1	0.5	1.31 ± 0.73	2.09 ± 0.52ns	3.27 ± 0.88ns
K. pneumoniae DIN	+	+	4	2	2	1.5	1.5	6.21 ± 1.08	3.88 ± 1.26ns	7.91 ± 1.45ns

^a−, absence of the corresponding gene; +, presence and expression of the corresponding gene.

^b−, no growth.

^cND, not determined; ^ns, not significant. Statistical analysis was performed on the results of 3 independent experiments using Student's t test. P values of <0.05 were considered significantly different.