The Bacteriostatic Effects of Orally Administered Bovine Lactoferrin on Intestinal Enterobacteriaceae of SPF Mice Fed Bovine Milk

Abstract

The number of faecal Enterobacteriaceae increased greatly in SPF mice fed bovine milk compared to SPF mice fed a commercial pelleted diet (F-2, Funabashi Farm Co., Chiba, Japan). As dominant species of Enterobacteriaceae, Escherichia coli, and Proteus mirabilis were isolated from mice feces. When mice were fed milk with bovine lactoferrin (bLF) added, the faecal bacterial number decreased to the level found in the feces of mice fed the pelleted diet (F-2). Administered bLF also caused suppression of the initial proliferation of faecal Enterobacteriaceae in the milk-fed mice. This result indicates a bacteriostatic effect of bLF in vivo. The bacteriostatic effect of administered bLF was dependent on the concentration of bLF and the duration of feeding, but independent of the iron-chelating ability of bLF. Compared with other proteins, only bLF showed this specific activity. The same effect was observed in each part of the gastrointestinal tract of mice fed bLF-containing milk. A hydrolysate of bLF digested with porcine pepsin showed the same effect on the faecal bacteria as native bLF. These results indicate that administered bLF has a bacteriostatic effect against Enterobacteriaceae in the gut even after it has been digested to some extent.