Inactivation of Listeria monocytogenes by Lactoferricin, a Potent Antimicrobial Peptide Derived from Cow's Milk.

The susceptibility of Listeria monocytogenes to inhibition and inactivation by lactoferricin, a newly isolated antimicrobial peptide derived from bovine lactoferrin present in cow's milk, was studied in laboratory media. Lactoferricin showed an effectiveness similar to that of many clinically useful antibiotics, causing complete inhibition of four strains of L. monocytogenes (serotypes 1b, 2, 3, and 4a) at low concentrations varying within the range of 0.3 to 9 μg/ml depending on the strain and the culture medium used. The effectiveness of lactoferricin against L. monocytogenes was not strongly affected by the presence of various carbohydrates or proteins but was somewhat diminished in the presence of various salts. The peptide showed potent activity over the pH range of 5.5 to 7.5. The effect of lactoferricin was lethal, causing a rapid loss of colony-forming ability with all four strains tested.