TABLE 1.

Minimum inhibitory concentrations of ampicillin for omega loop mutants

E. coli containing TEM-1 plasmids	Broth dilution MIC	Etest MIC
	μg/ml	μg/ml
E. coli XL-1 Blue	2	1.5
pTP123	2	1.5
Wild-type TEM-1	2048	>256
N170G	2048	>256
E166A	4	2
E166A/N170G	8	4