Table 3.

Composition of lipid A in colistin-resistant and -susceptible A. baumannii clinical pair Ab15/133 and Ab15/32 and in ATCC 19606 and ABRIM and their derivatives

Peak (m/z)	Chemical inference	Chemical compositiona	Presence/absence of chemical interference in:
			Ab15/133 (colistin susceptible)	Ab15/132 (colistin resistant)	ABRIM ColS (colistin susceptible)	ABRIM ColR (colistin resistant)	ATCC 19606 ColS (colistin susceptible)	ATCC 19606 ColR (colistin resistant)	ATCC 19606 ColS ΔpmrB (colistin susceptible)	ATCC 19606 ColR ΔpmrB (colistin susceptible)
1,404	Tetra-acylated lipid A	2 glucose residues	+	+	+	+	+	+	+	+
		2 phosphates
		3 acyl groups, 12:0(3-OH)
		1 acyl group, 14:0(3-OH)
1,530	Penta-acylated lipid A	2 glucose residues	+	−	+	−	−	−	−	−
		2 phosphates
		2 acyl groups, 12:0(3-OH)
		2 acyl groups, 14:0(3-OH)
		1 acyl group, 12:0
1,728	Hexa-acylated lipid A	2 glucose residues	+	−	+	−	+	−	+	+
		2 phosphates
		3 acyl groups, 12:0(3-OH)
		2 acyl groups, 14:0(3-OH)
		1 acyl group, 12:0
1,910	Hepta-acylated lipid A	2 glucose residues	+	+	+	+	+	+	+	+
		2 phosphates
		3 acyl groups, 12:0(3-OH)
		2 acyl groups, 14:0(3-OH)
		2 acyl groups, 12:0
2,034	Phosphoethanolamine-modified	2 glucose residues	−	+	−	+	−	+	−	−
	hepta-acylated lipid A	2 phosphates
		3 acyl groups, 12:0(3-OH)
		2 acyl groups, 14:0(3-OH)
		2 acyl group, 12:0
		1 phosphoethanolamine

^aFig. 4.