A Lipoprotein‐derived Antimicrobial Factor from Hen‐egg Yolk is Active Against Streptococcus Species

: Oral administration of hen-egg yolk provides protection against specific pathogens. We examined the antibacterial activity of fractionated egg yolk against 2 pathogenic Streptococcus strains, using an in vitro assay. A water-soluble protein fraction (WSPF) of egg yolk consistently inhibited the growth of S. mutans by 25%. The WSPF treated with pancreatin demonstrated > 80% inhibition of bacterial growth. Growth of S. sanguis was completely inhibited. Gel filtration and ion exchange chromatography established that anti-Streptococcal activity resided with lipoproteins. Antibacterial activity was released by crude lipase or a combination of lipase and protease treatment of egg lipoproteins. Thus, hen-egg yolk lipoproteins are important molecules for lipid-mediated antimicrobial activity.