Table 4.

Minimal concentrations of CBD and PB (PB minimal effective antibiotic concentration [MEAC]) required to the antibacterial activity of the combination CBD + PB, according to checkerboard assay results. Plasmid-mediated colistin-resistant (MCR-1) E. coli 72H and P. aeruginosa strains (ATCC 27853 and HC 103) were assessed in the presence of 50 µg/mL of PAβN.

Strain	Antibacterial activity of the combination CBD + PB (µg/mL)		PB MIC (µg/mL)	PB MIC versus PB MEAC (two-fold differences)
	CBD	PB MEAC
K. pneumoniae ATCC 13883a	4	0.03	8	8
K. pneumoniae ATCC BAA-1705	4	0.25	0.5	1
K. pneumoniae C9b	4	2	64	5
K. pneumoniae D1b	4	0.25	1	2
K. pneumoniae RP 62c	2	1	32	6
K. pneumoniae L8	2	≤ 1	128	8
K. pneumoniae L13	2	≤ 0.25	32	8
K. pneumoniae L17	4	2	32	5
K. pneumoniae L22	2	≤ 0.5	256	10
K. pneumoniae L28	2	≤ 0.5	32	7
K. pneumoniae L29	2	≤ 0.5	32	7
K. pneumoniae L34	2	0.5	32	7
E. coli ATCC 25922	4	0.06	0.5	3
E. coli CTX-M-15	8	0.03	0.5	4
E. coli 72Hd (MCR-1)	4 + PAβN	1	2	1
E. coli NCTC 13846 (MCR-1)	4 + PAβN	1	2	1
A. baumannii ATCC 19606a	4	0.125	1	3
A. baumannii 136 SPe	1	0.25	1	2
P. aeruginosa ATCC 27853	4 + PAβN	0.03	1	5
P. aeruginosa HC 103f	4 + PAβN	0.03	2	6

ATCC American Type Culture Collection.

^aType strain.

^bPalmeiro et al.²⁵.

^cAndrade et al.²⁶.

^dFernandes et al.²⁷.

^eClímaco et al.³⁰.

^fGaletti et al.²⁹.