Mutations in Confer Cross-Resistance between the LptD Inhibitor POL7080 and Colistin in .

is a major bacterial pathogen associated with a rising prevalence of antibiotic resistance. We evaluated the resistance mechanisms of against POL7080, a species-specific, first-in-class antibiotic in clinical trials that targets the lipopolysaccharide transport protein LptD. We isolated a series of POL7080-resistant strains with mutations in the two-component sensor gene Transcriptomic and confocal microscopy studies support a resistance mechanism shared with colistin, involving lipopolysaccharide modifications that mitigate antibiotic cell surface binding.