TABLE 1.

MICs of several antibiotics for DHA-1, DHA-6, and DHA-7 β-lactamases in different bacterial strains

Antibiotic	MIC (mg/liter) fora:
	E. coli TG1 pBGS18-pCTX	K. oxytoca 33/002 (DHA-1)	E. coli 30/021 (DHA-6)	E. cloacae 30/034 (DHA-7)	E. coli TG1 pBGS18-pCTXb (DHA-1)	E. coli TG1 pBGS18-pCTX (DHA-6)	E. coli TG1 pBGS18-pCTX (DHA-7)
Ampicillin	2	2,056	512	>2,056	1,028	256	2,056
Ampicillin-clavulanic acidc	2	2,056	512	>2,056	1,028	256	2,056
Ampicillin-sulbactamc	2	128	128	2,056	128	128	2,056
Ampicillin-tazobactamc	2	32	64	>2,056	64	128	2,056
Cephalothin	4	512	512	>1,028	1,028	256	1,028
Cefoxitin	1	128	32	64	32	128	64
Ceftazidime	0.06	4	16	128	32	4	128
Cefotaxime	0.06	4	4	32	8	1	32
Cefepime	<0.12	0.12	0.12	8	0.5	0.12	0.12
Aztreonam	0.12	16	2	128	8	2	32
Imipenem	<0.03	0.25	0.5	4	0.12	0.06	0.12

^aClinical isolates that harbor the β-lactamase gene are shown in parentheses.

^bpBGS18, pCTX plasmid expressing the indicated β-lactamases under the control of an external promoter.

^cAmpicillin was tested when indicated with fixed concentrations of clavulanic acid, sulbactam, or tazobactam (4 mg/liter).