Table 4.

Fractional inhibitory concentration (FIC) indexes (FICIs) of combined effects among major active compounds (crude extract, fraction 5, and pure compound), standard compounds (Penta-galloyl-glucose and pyrogallol), and antibiotics against methicillin-resistant Staphylococcus aureus KCCM 40511.

Strain	Antibiotics	Compound**	MIC (μg/mL)		∑FICmaxa)	∑FICminb)	FICIc)
			Alone	Combination
MRSA KCCM 40511*	Ampicillin	CE	256	32	2.250	0.625	1.031
		AMP	256	128
		F5	16	0.016	1.250	0.750	1.031
		AMP	256	256
		SC	16	2	1.250	0.625	1.031
		AMP	256	256
		PGG	128	64	1.063	0.625	0.844
		AMP	256	128
		PG	128	2	1.000	0.125	0.262
		AMP	256	64
	Oxacillin	CE	256	0.25	1.500	0.501	0.531
		OXA	128	64
		F5	16	4	0.625	0.500	0.562
		OXA	128	32
		SC	16	2	0.313	0.188	0.281
		OXA	128	8
		PGG	128	1	0.125	0.064	0.070
		OXA	128	8
		PG	128	4	2.000	0.250	0.773
		OXA	128	64
	Clavulanic acid	CE	256	256	2.000	2.000	2.000
		CLA	32	32
		F5	16	8	2.000	1.500	1.750
		CLA	32	32
		SC	16	8	2.000	1.500	1.750
		CLA	32	32
		PGG	128	32	1.125	0.281	0.434
		CLA	32	8
		PG	128	-	-	-	-
		CLA	32	-

^a)ΣFIC_max, maximum FIC value; ^b)ΣFIC_min, minimum FIC value; ^c)FICI, The FIC index indicated synergistic effect: <0.5, marked synergy; 0.5 to <1.0, weak synergy; 1.0, additive; >1.0 to <2.0, subadditive; 2.0, indifferent; >2.0, antagonistic.

*MRSA KCCM 40511 is a standard strain purchased from KCCM; isolated strains were provided by Dong-A University Hospital. **CE, Crude extract with 40% Ethanol; F4, fraction 4; F5, fraction 5; F6, fraction 6; SC, single compound; PGG, pentagalloyl-glucose (standard compound 1); PG, pyrogallol (standard compound 2).