FORMS OF LACTOFERRIN - THEIR ANTIBACTERIAL EFFECT ON ENTEROTOXIGENIC ESCHERICHIA-COLI

The antibacterial effects of various forms of lactoferrin on enterotox igenic strains of Escherichia coli were tested in vitro using a microa ssay for bacterial growth. Native and apo-lactoferrin exhibited variab le activity against 19 strains, whereas holo-lactoferrin had no effect . At a concentration of .2 mg/ml of apo-lactoferrin, strains could be distinguished as either sensitive or resistant to inhibition. Zinc-sat urated lactoferrin was as inhibitory as apo-lactoferrin when sensitive and resistant strains were tested over the concentration range .04 to 1.0 mg/ml of lactoferrin. A bactericidal effect was observed for nati ve, apo-, and Zn-saturated lactoferrin against some sensitive strains. The antibacterial activity of apo-lactoferrin depended on bacterial i noculum size and was not enhanced by the addition of lysozyme. Additio n of holo-lactoferrin or cytochrome c diminished the antibacterial eff ect of apo-lactoferrin, whereas addition of BSA had no effect. Resista nce to inhibition by lactoferrin was not related to the production of bacterial siderophores.