lactoferrin and Enterobacteriaceae-Infections

Cronobacter sakazakii is now recognized as an opportunistic pathogen and has been implicated in rare but severe cases of necrotizing enterocolitis, meningitis, and sepsis in neonates. The first step in bacterial pathogenesis requires that the organism adheres to host cells surfaces; therefore, agents that inhibit adherence might be useful for preventing infections. Lactoferrin, an iron binding protein found in milk, has been shown to inhibit bacterial adherence by direct interaction and disruption of bacterial surfaces. Therefore, the goal of this research was to assess the ability of two different types of bovine lactoferrin, alone and in combination with a 1:1 blend of galactooligosaccharides and polydextrose, to inhibit adherence of C. sakazakii to a HEp-2 human cell line. Results showed that the adherence of C. sakazakii was significantly reduced at a minimum lactoferrin concentration of 10 mg/ml. However, in combination with the oligosaccharide blend, no synergistic effect was observed in adherence inhibition. These results suggest that lactoferrin might interact with C. sakazakii and directly inhibit adhesion to tissue culture cells.

Topics: Animals; Bacterial Adhesion; Cattle; Cronobacter sakazakii; Down-Regulation; Enterobacteriaceae Infections; Epithelial Cells; Hep G2 Cells; Humans; Intestines; Lactoferrin

Intelectins (IntL) are Ca(2+)-dependent secretory glycoproteins that play a role in the innate immune response. The mammalian IntL is also known as lactoferrin receptor (LfR) that is involved in iron metabolism. The objective of this study was to characterize the intelectin genes in both channel catfish and blue catfish, to determine their genomic organization and copy numbers, to determine their patterns of tissue expression, and to establish if they are involved in defense responses of catfish after bacterial infection. Two types of IntL genes have been identified from catfish, and IntL2 was completely sequenced. The genomic structure and organization of IntL2 were similar to those of the mammalian species and of zebrafish and grass carp, but orthologies cannot be established with mammalian IntL genes. The IntL genes are highly conserved through evolution. Sequence analysis also indicated the presence of the fibrinogen-related domain in the catfish IntL genes, suggesting their structural conservations. Phylogenetic analysis suggested the presence of at least two prototypes of IntL genes in teleosts, but only one in mammals. The catfish IntL genes exhibited drastically different patterns of expression as compared to those of the mammalian species, or even with the grass carp gene. The catfish IntL1 gene is widely expressed in various tissues, whereas the channel catfish IntL2 gene was mainly expressed in the liver. While the catfish IntL1 is constitutively expressed, the catfish IntL2 was drastically induced by intraperitoneal injection of Edwardsiella ictaluri and/or iron dextran. Such induction was most dramatic when the fish were treated with both the bacteria and iron dextran. While IntL1 was expressed in all leukocyte cell lines, no expression of IntL2 was detected in any of the leukocyte cell lines, suggesting that the up-regulated channel catfish IntL2 expression after bacterial infection may be a consequence of the initial immune response, and/or a downstream immune response rather than a part of the primary immune responses.

Topics: Amino Acid Sequence; Animals; Cytokines; Edwardsiella ictaluri; Enterobacteriaceae Infections; Fish Diseases; Fishes; Gene Expression Profiling; Gene Expression Regulation; GPI-Linked Proteins; Ictaluridae; Immunity, Innate; Iron; Lactoferrin; Lectins; Molecular Sequence Data; Organ Specificity; Phylogeny; Sequence Alignment; Sequence Analysis, DNA

Recently we have reported that orally administered bovine Lf(bLf) exerts bacteriostatic effects against bacterial overgrowth in the intestine of specific-pathogen-free (SPF) mice fed milk. In this animal model, the in vivo bacteriostatic effect of bLf against the proliferation of intestinal Enterobacteriaceae, the bacteria most sensitive to bLf, was independent of the iron-chelating ability of bLf. In addition various proteolytic hydrolysates of bLf (with differing antibacterial activities in vitro) showed the same bacteriostatic effect as undigested bLf. These results suggest that the mechanism of in vivo bacteriostasis of Lf differs from the in vitro mechanism reported. In SPF mice fed milk differing in concentrations of lactose, glucose and galactose, the proliferation of intestinal Enterobacteriaceae was dependent on the carbohydrate concentration in the diet. The addition of 2% bLf to the diets significantly suppressed this carbohydrate-dependent proliferation of bacteria except in the case of diets containing excess carbohydrate. In germ-free mice fed sterile milk, the addition of 2% bLf to milk resulted in a significant decrease in concentrations of lactose, glucose and galactose in the cecal contents. In an in vitro assay system using everted sacs of the small intestine of SPF mice, both bLf and its pepsin hydrolysate apparently stimulated glucose absorption. Based on these findings, we propose that the in vivo mechanism of action of ingested bLf involves the stimulation of carbohydrate absorption resulting in a bacteriostatic effect against Enterobacteriaceae in the intestine of mice fed milk.

Topics: Animals; Anti-Bacterial Agents; Carbohydrate Metabolism; Cattle; Enterobacteriaceae; Enterobacteriaceae Infections; Lactoferrin; Mice; Mice, Inbred BALB C