As bacterial resistance becomes increasingly common, a new hybrid peptide, cecropinA-magainin (KWALSKEGPGKFLGKKKKF), has been developed that can kill a broad spectrum of bacteria without damaging human cells. The mechanism of antibacterial toxicity for the hybrid peptides is unknown. Herein, we investigate the localization of the hybrid peptide in methicillin-resistant Staphylococcus aureus (MRSA). The minimum inhibitory concentration was 64 mu g/mL. The hybrid peptides could enhance the hydrophobicity of MRSA. Dye leakage experiments showed that the hybrid peptides caused dye leakage from liposomes. The hybrid peptides influenced the permeability of the outer membrane and plasma membrane of MRSA. After cecropinA-magainin treatment of MRSA, the membrane ultrastructure was damaged and the concentration of K+ increased. Ultimately, the peptide destroyed the integrity of the bacterial cell membrane, allowing the dye propidium iodide to enter the cytoplasm. Therefore, the hybrid antibacterial peptide can kill MRSA. (C) 2015 International Union of Biochemistry and Molecular Biology, Inc. Volume 63, Number 6, Pages 805-811, 2016