Bacteriostatic activity of bovine milk lactoferrin against mastitic bacteria.

The bacteriostatic activity of bovine lactoferrin (Lf) against mastitic bacteria was assessed with an in vitro microassay. The most susceptible species was Escherichia coli; all of the 35 isolates tested were susceptible to bacteriostasis by apo-Lf (0.1 mg ml-1), although a few strains showed a lower degree of inhibition. Heterogeneity among strains was more pronounced among 10 isolates of Staphylococcus aureus, four of which were apparently unaffected by apo-Lf (1 mg ml-1). Under the same conditions, Streptococcus agalactiae (six isolates) and Str. uberis (five isolates) resisted the bacteriostatic action of apo-Lf.