The novel polymyxin analogue SPR206 exhibits higher activity than colistin against both colistin-susceptible and colistin-resistant strains of Acinetobacter baumannii.

Colistin resistance is increasing globally and complicates treatments of A. baumannii infections. The next-generation polymyxin SPR206 shows potent activity against multidrug-resistant Gram-negative pathogens with low toxicity. SPR206 exhibited higher activity against colistin-susceptible and colistin-resistant strains (MIC50/MIC90 = 0.12/0.25 mg/L), and resistance was only detected in 1/118 strains (MIC ≥4 mg/L). Mutations in pmrCAB, linked to colistin resistance, do not seem to confer resistance to the novel polymyxin, which retains a high level of activity.