Antimicrobial peptides of the formula are provided: X1—X2—PrO—X3—X4—PrO-Arg-Pro-Tyr-Leu-Pro-X5-Pro-Arg-Pro-Pro-Arg-Pro-Y, wherein X1 is a natural or non-natural amino acid having a free amino group or 1-amino-cyclohexyl carboxylic acid, X2 is Arg or N-methyl-Arg, X3 is Asp or GIu, X4 is Arg or Lys, X5 is Arg or Lys, and Y is Arg, Arg-NH2, N-methyl-Arg, N-methyl-Arg-NH2, Val-Arg, Val-Arg-NH2, Val-(N-methyl-Arg), or Val-(N-methyl)-Arg-NH2, and salts thereof.