Post-antibiotic effect of the antimicrobial peptide lactoferricin on Escherichia coli and Staphylococcus aureus

Lactoferricin is an antimicrobial peptide generated by gastric pepsin cleavage of lactoferrin. A possible post-antibiotic effect (PAE) of bovine lactoferricin (Lfcin B) and two shorter peptide derivatives against Staphylococcus aureus and Escherichia coli was studied. A drug removal technique involving centrifugation and washing was used. No PAE was found for Lfcin B against these two bacteria. The shorter derivatives had a short PAE against E. coli. They had a short negative PAE against S. aureus. In conclusion, the overall PAE is not overwhelming, but the small differences found between the different peptide-bacteria combinations could indicate that different peptide mechanisms of action might be present.