A method for treating an infection comprises administering a peptide insynergisticcombination with an antibiotic, wherein the peptide comprises an amino acidsequence witha formula selected from the group consisting of:(a) B n1 - Z；(b) B n1 - Z - B n2； and(c) Z - B n1wherein B is a basic amino acid residue；n1 and n2 are 1 to 6； andZ is a sequence of from about 7 to about 24 amino acid residues, said sequencehaving an average hydrophobicity value of at least 0.3 on the Liu-Deber scale.
