Insertion Sequence ISAba11 Is Involved in Colistin Resistance and Loss of Lipopolysaccharide in Acinetobacter baumannii

Infections caused by Acinetobacter baumannii are of increasing concern, largely due to the multidrug resistance of many strains. Here we show that insertion sequence ISAba11 movement can result in inactivation of the A. baumannii lipid A biosynthesis genes lpxA and lpxC, resulting in the complete loss of lipopolysaccharide production and high-level colistin resistance.