TABLE 4.

Checkerboard assay results for antibiotic-compound 79 synergy in E. coli ATCC 25922 and MDR CTX-M-15-producing ST131 strains

Antibiotic or compound	ATCC 25922			ST131
	MIC alonea	MIC at FIC indexb	FIC indexc	MIC alone	MIC at FIC index	FIC index
Erythromycin	16	1	0.19	256	16	0.19
Fusidic acid	500	16	0.16	500	4	0.14
Novobiocin	16	0.5	0.16	16	2	0.25
Rifampin	2	0.03	0.14	4	0.25	0.19
Compound 79	2	0.25	NAd	2	0.25	NA

^aMIC of each antibiotic (μg/ml) or compound (μM) individually.

^bMIC in compound-antibiotic combination at the lowest fractional inhibitory concentration index.

^cFIC index, fractional inhibitory concentration index.

^dNA, not applicable.