TABLE 1.

β-Lactam susceptibility of strains expressing PenA and its mutant derivatives

Strain	MIC (μg/ml)a
	Ampicillin	Carbenicillin	Ceftazidime	Imipenem
Bp82	128	1,024	4	1
Bp82 ΔpenA	8	16	1	0.25
Bp82 penAC23S	16	128	1b	0.25
Bp82 penAI20A C23S	256	1,024	4	1

^aMICs obtained were determined by the broth microdilution method unless indicated otherwise.

^bThis value was obtained by the agar dilution method.