TABLE 5.

Potentiation of antimicrobial activity against β-lactamase producers

Sp. and strain	Type of class B β-lactamase	MICa (μg/ml) of drug:					FIC indexb
		Imipenem alone	Ceftazidime alone	J-110,441 alone	Imipenem + 1/4 MIC of J-110,441	Ceftazidime + 1/8 MIC of J-110,441
S. marcescens
BB6231	IMP-1	64	>128	128	4		0.31
BB6232	IMP-1	64	128	256	4		0.31
BB6233	IMP-1	256	>128	256	4		0.27
BB6234	IMP-1	256	>128	128	16		0.31
BB5886	IMP-1	256	>128	64	64		0.50
P. aeruginosa
BB6298	IMP-1	16	>128	128	4		0.50
GN17203	IMP-1	128	>128	128	64		0.75
S. maltophilia
BB6299	L1	128	>128	32	128		1.25
GN12873	L1	128	>128	64	32		0.50
B. fragilis GAI30079	CcrA	64	>128	32	16		0.50
E. cloacae GN7471	—c	0.5	64	32		4	0.19

^aDetermined by broth microdilution method. 

^bFIC index: ≤0.5, synergism; 1.0, additivity; >2.0, indifference or antagonism. 

^c—, not produced.