Synergistic effect of antimicrobial peptide LL-37 and colistin combination against multidrug-resistant Escherichia coli isolates

The global spread of antibiotic resistance represents a serious threat for public health. Aim: We evaluated the efficacy of the antimicrobial peptide LL-37 as antimicrobial agent against multidrug-resistant Escherichia coli. Results: LL-37 showed good activity against mcr-1 carrying, extended spectrum β-lactamase- and carbapenemase-producing E. coli (minimum inhibitory concentration, MIC, from 16 to 64 mg/l). Checkerboard assays demonstrated synergistic effect of LL-37/colistin combination against all tested strains, further confirmed by time–kill and post antibiotic effect assays. MIC and sub-MIC concentrations of LL-37 were able to reduce biofilm formation.