Antibacterial effects of lactoferricin B

The antimicrobial peptide, lactoferricin, can be generated upon gastric pep sin cleavage of lactoferrin. We have examined the inhibitory efficacy of La ctoferricin of bovine origin (Lf-cin B) on Escherichia coli, Proteus mirabi lis and Staphylococcus aureus with or without a cell wall. We found that sp heroplasts and protoplasts had a lower MIC than their counterparts with a c ell wall. We also compared the efficacies of Lf-cin B (17-31) made of all L -amino acids and all D-amino acids. The peptide made of all D-amino acids w as more active than the corresponding L-enantiomer. Furthermore, we examine d the influence of Lf-cin B on the motility of E. coli and the influence of temperature on the susceptibility of bacteria exposed to Lf-cin B. Bacteri a exposed to sub-MIG of Lf-cin B lost their motility. Bacteria exposed to L f-cin B at 20 degrees C were more sensitive to Lf-cin B than when exposed a t 37 degrees C. These findings indicate that the cell envelope is a limitin g step for Lf-cin B to exert its antibiotic effect. We cannot rule out a re ceptor-mediated first step for Lf-cin B (17-31).