TABLE 1.

Checkerboard assays showing the effects of colistin combined with auranofin.

Pathogen	Strains	Source	Mechanism of colistin resistance	MIC(mg/L)				FICI
				Col	Aur	ColAur	AurCol
K. pneumoniae	ATCC700603	ATCC	Colistin susceptible	1	512	0.5	8	0.516
	12959	BALF	PmrA G53V	64	128	0.5	4	0.039
	15979	Sputum	ISKpn14 at nt115 of mgrB	64	256	1	4	0.031
	13649	BALF	ISKpn14 at nt126 of mgrB	128	256	2	2	0.023
	13568	BALF	PmrA G53V	64	64	1	4	0.078
	18605	Wound	ISKpn14 at nt115 of mgrB	128	256	2	2	0.023
	18229	BALF	PhoQ A63E	256	512	1	4	0.012
	C505	Sputum	mcr-8	8	128	0.5	2	0.078
	C270	Urine	mcr-8	16	128	1	1	0.07
	17-R27	Liver	mcr-1	32	256	1	4	0.047
	09-20	Blood	mcr-1	16	256	0.5	2	0.039
E. coli	ATCC25922	ATCC	Colistin susceptible	0.5	512	0.5	2	1.004
	C297	Liver	ND	1024	32	0.5	8	0.25
	C1052	Urine	PmrB D283G	64	64	2	2	0.063
	C1157	Sputum	PhoQ V413F	64	64	1	1	0.031
	C1279	Urine	PmrA S29G	64	64	0.5	1	0.023
	C1461	Urine	PmrB Y358M, PhoP I44L	32	64	0.5	2	0.047
	17-R14	Liver	mcr-1	4	8	0.25	2	0.313
	08-85	Blood	mcr-1	8	16	1	1	0.188
P. aeruginosa	ATCC27853	ATCC	Colistin susceptible	1	512	1	2	1.004
	26751	BALF	PhoP V99L	128	512	4	4	0.039
	26587	BALF	PhoP V99L	512	512	2	8	0.02
	26683	BALF	ND	64	512	4	0.5	0.063
A. baumannii	ATCC19606	ATCC	Colistin susceptible	1	16	0.5	2	0.625
	13660	Sputum	PmrA T119S	512	32	2	4	0.129
	26701	Sputum	ND	512	128	1	4	0.033
	29831	Urine	ND	256	128	2	2	0.023

BALF, bronchoalveolar lavage fluid; Col, colistin; Aur, auranofin; FICI, fractional inhibitory concentration index; and ND, not determined.