TABLE 4.

Synergy of niclosamide with colistin against MDR/XDR colistin-resistant Gram-negative bacilli, including mcr-1 gene-positive E. coli strains

Organism	MICNIC [MICcombo], μg/ml	MICCOL [MICcombo], μg/ml	FIC index	Absolute MICCOL,a μg/ml	Potentiation (fold)b
P. aeruginosa 91433	4 [0.125]	4 [0.062]	0.047	≤0.016	≥256
P. aeruginosa 101243	>256 [0.25]	1024 [0.25]	0.0002 < x < 0.001	≤0.062	≥16,384
P. aeruginosa 114228	>256 [16]	4 [1]	0.250 < x < 0.312	2	2
A. baumannii 82479	>64 [2]	>64 [1]	<0.047	2	>32
A. baumannii 92247	>64 [8]	8 [0.125]	0.016 < x < 0.141	0.25	32
K. pneumoniae 106931	>64 [4]	64 [0.25]	0.004 < x < 0.066	1	64
K. pneumoniae 110036	>64 [8]	8 [0.25]	0.031 < x < 0.156	2	4
K. pneumoniae 113250	>256 [0.5]	256 [0.25]	0.001 < x < 0.003	0.125	2,048
K. pneumoniae 113254	>256 [0.5]	256 [0.5]	0.002 < x < 0.004	0.125	2,048
E. coli 94393c	>64 [8]	4 [0.25]	0.062 < x < 0.187	1	4
E. coli 94474c	>64 [8]	16 [0.5]	0.031 < x < 0.156	2	8
E. cloacae 118564	>64 [8]	>64 [0.125]	<0.127	0.5	>128
E. cloacae 121187	>64 [4]	>64 [0.125]	<0.064	0.5	>128

^aMIC of colistin in the presence of 1 μg/ml (3 μM) niclosamide.

^bDegree of colistin potentiation in the presence of 1 μg/ml (3 μM) niclosamide.

^cmcr-1 gene positive.