Many antimicrobial peptides (AMP's) target the structural integrity of the cell membrane. The differences between human cell membrane and bacteria membrane can lend to a more targeted approach of attacking the pathogen but leaving the patient's cells unaltered. The AMP dubbed "NKCS" showed impressive selectivity in this paper by Ciobanasu, Rzeszutek, Kubitscheck and Willumeit. The selectivity was tested with model membranes made of phosphatidylcholine for human cells and phosphatidylethanolamine/phosphatidylglycerol to mimic E. coli membrane. Using tracers they were able to observe NKCS's interactions with the membranes. Outflow tracer experiments demonstrated NKCS's ability to induce a breach in the membrane that allowed tracers to escape.

Read more here: http://www.mdpi.com/1420-3049/20/4/6941/htm