TABLE 2.

β-lactamase activities for clinical E. coli isolates, C. freundii 31A12, and E. coli TB1 carrying pTZ18U

Strain	Description	β-Lactamase activitya
		Without clavulanate	With 1 μM clavulanate
E. coli 69	Imipenem sensitive	1,182	855
E. coli 68	Imipenem intermediate	151	90
E. coli 79	Imipenem resistant	863	646
C. freundii 31A12	High-level AmpC β-lac-tamase producer	273	239
E. coli TB1(pTZ18U)	High-level TEM-1 β-lac-tamase producer	4,667	190

^aActivities are expressed as nanomoles of nitrocefin hydrolyzed per minute per milligram of protein.