Antibacterial activity of lactoferricin, lysozyme and EDTA against Salmonella enteritidis

The antibacterial activity of a pepsin digest of bovine lactoferrin, containing the peptide lactoferricin B against Salmonella enteritidis was studied under various conditions. The digest had greater antibacterial activity than lactoferrin in 1% peptone, was bactericidal and also increased the permeability of the outer membrane of the bacteria as demonstrated by plating on bile salts agar. The antibacterial activity was inhibited in richer media, such as tryptic soy broth or milk-based or soy-based infant formula. Addition of lysozyme or EDTA or both, to the lactoferrin digest resulted in increased antibacterial activity of the mixture. Lysosyme or EDTA alone had little or no activity against S. enteritidis. The increase in antibacterial activity obtained with the addition of lysozyme and EDTA to the lactoferrin digest was not sufficient to overcome inhibition by components of the richer media.