Lactoferrin is an iron-binding protein that occurs in milk and colostrum and has potential for use as a food antimicrobial (78). Lactoferrin is a glycoprotein with a molecular weight of around 76,500 Da. Lactoferrin has two iron-binding sites per molecule and, for each Fe3+ bound, requires one bicarbonate (hco3 ). Lactoferrin is potentially active in milk due to the low iron concentration and presence of bicarbonate (79). The exact biological role of lactoferrin is unknown; however, it may act as a barrier to infection of the nonlactating mammary gland and protect the gastrointestinal tract of the newborn against infection (78).
Lactoferrin is inhibitory to a number of microorganisms including Bacillus subtilis, B. stearothermophilus, Listeria monocytogenes, Micrococcus, E. coli, and Klebsiella (18). There is evidence that the most effective form of lactoferrin is the iron-unsaturated, or apolactoferrin, form (80). Some Gram-negative bacteria may be resistant because they adapt to low-iron environments by producing siderophores such as phenolates and hydroxamates. Microorganisms with a low iron requirement, such as lactic acid bacteria, would not be inhibited by lactoferrin (78).
Lactoferricin B is a small peptide (25 amino acids) produced by acid-pepsin hydrolysis of bovine lactoferrin (81). The compound is inhibitory to Shigella, Salmonella, Yersinia enterocolitica, E. coli 0157:H7, Staphylococcus aureus, L. monocytogenes, and Candida species at concentrations ranging from 1.9 to 125 mg/mL (82). Another iron-binding molecule, ovotransferrin or conalbumin, occurs in egg albumen. Each ovotransferrin molecule has two iron-binding sites and, like lactoferrin, it binds an anions, such as bicarbonate or carbonate with each ferric iron bound. Ovotransferrin is inhibitory against both Grampositive and Gram-negative bacteria, but the former are generally more sensitive, with Bacillus and Micrococcus species being particularly sensitive (75). Some yeasts are also sensitive.
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The term vaginitis is one that is applied to any inflammation or infection of the vagina, and there are many different conditions that are categorized together under this ‘broad’ heading, including bacterial vaginosis, trichomoniasis and non-infectious vaginitis.