INHIBITION OF BACTERIA BY LACTOFERRIN AND OTHER IRON-CHELATING AGENTS

When not fully saturated with iron, bovine, human and goat lactoferrins were bacteriostatic for Bacillus stearothermophilus and Bacillus subtilis in both the presence and absence of trace amounts of metals. Bovine lactoferrin inhibited the germination of spores and the growth of vegetative cells of B. stearothermophilus. The bacteriostatic action of lactoferrin was suppressed by Fe2+ and enhanced by Zn2+, Co2+, Mn2+, Ni2+ and Cu2+. Although B. stearothermophilus was also inhibited by 8-hydroxyquinoline and 1,10-phenanthroline, other iron-binding agents, including transferrins from several different sera were non-inhibitory. B. stearothermophilus and B. subtilis were also inhibited by a high-molecular-weight complex isolated from the secretion of non-lacting cows. The complex contained lactoferrin and casein and although its activity was suppressed by the addition of iron, it had a higher heat stability than purified lactoferrin and was not precipitated by antibody to lactoferrin. © 1968.