This invention relates to modified antibiotic peptides, particularly for use in medicine. The invention further relates to composite and methods for destroying microorganisms, such as bacteria, viruses or fungi, and to methods for treating microbial infections. The object of the invention is to develop novel antibiotic peptides, particularly having enhanced antibiotic activity and an expanded spectrum of activity against other strains of bacteria, particularly gram-positive bacteria such as Staphylococcus aureus. According to the invention, the object is attained in a first aspect by a peptide according to claim 1.