TABLE 2.

Combination activities of NG with colistin.

Species	Strains	Mechanism of colistin resistance	Monotherapy (μg/ml)		Combination (μg/ml)		FICI	Interpretation
			COL	NG	COL	NG
K. pneumoniae	FK1913	MgrB (K2E, F28C), PhoQ (D150G)	>64	>512	2	64	<0.155	Synergistic
	FK6663	PmrB (R256G), mcr-1	8	>512	2	64	<0.375	Synergistic
	FK169	MgrB (K2E, F28C)	>64	>512	1	128	<0.265	Synergistic
	FK6556	PmrB (R256G), mcr-1	16	>512	2	128	<0.375	Synergistic
	FK1342	MgrB (K2E, F28C), PhoQ (D150G), mcr-1	>64	>512	2	128	<0.281	Synergistic
	FK1986	MgrB (K2E, F28C), PhoQ (D150G)	8	>512	2	64	<0.375	Synergistic
	FK3994	PmrB (R256G), mcr-1	64	>512	2	64	<0.155	Synergistic
E. coli	DC3846	mcr-1	8	>512	1	128	<0.375	Synergistic
	DC7333	mcr-1	8	>512	1	128	<0.375	Synergistic
	DC3539	mcr-1	8	>512	1	128	<0.375	Synergistic
	DC3806	mcr-1	8	>512	2	64	<0.375	Synergistic
	DC5286	mcr-1	8	>512	2	64	<0.375	Synergistic
	DC90	mcr-1	4	>512	1	64	<0.375	Synergistic
	DC3737	mcr-1	8	>512	1	128	<0.375	Synergistic
A. baumannii	BM2349	PmrB (N163I), AdeABC/AdeIJK	4	>512	1	16	<0.28	Synergistic
	BM2431	PmrB (I10T), AdeABC/AdeIJK	32	>512	0.5	32	<0.077	Synergistic
	BM2412	LpxC (P46Q), AdeABC/AdeIJK	16	>512	1	32	<0.123	Synergistic
	BM2370	PmrB (W11R), LpxD (N148K), AdeABC/AdeIJK	8	>512	0.5	16	<0.09	Synergistic
	BM2622	LpxC (S186R), LpxD (T289I), PmrB (A138T), AdeABC/AdeIJK	4	>512	0.25	32	<0.123	Synergistic
	BM1595	PmrB (N163I), AdeABC/AdeIJK	8	>512	1	16	<0.156	Synergistic
	BM1539	LpxA (A182V), LpxC (P46Q), AdeABC/AdeIJK	8	>512	1	32	<0.187	Synergistic

FICI, fractional inhibitory concentration index; NG, Naringenin; COL, colistin.