Protective effects of synthetic antibacterial oligopeptides based on the insect defensins on Methicillin-resistant Staphylococcus aureus in mice.

Synthetic 9-mer peptides, ALYLAIRRR-NH2 and ALYLAIRKR-NH2, designed from the amino acid sequences of active sites of insect defensins, were examined for their protective effect on Methicillin-resistant Staphylococcus aureus (MRSA) in infected mice. These peptides protected mice from lethal MRSA challenges, despite having their antibacterial activity diminished in physiological high salt conditions. These peptides suppressed the induction of tumor necrosis factor alpha gene expression by lipopolysaccharide or lipoteichoic acid in murine macrophages, contributing to protection of mice from lethal MRSA infections in vivo. The results suggest that these peptides are potential candidates for future therapeutic agents against antibiotic-resistant bacterial infection.