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

The global spread of antibiotic resistance represents a serious threat for public health. We evaluated the efficacy of the antimicrobial peptide LL-37 as antimicrobial agent against multidrug-resistant . LL-37 showed good activity against -1 carrying, extended spectrum β-lactamase- and carbapenemase-producing (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. Our preliminary data indicated that LL-37/colistin combination was effective against multidrug-resistant strains and suggested a new possible clinical application.