Bactericidal activity of human lactoferrin: influence of physical conditions and metabolic state of the target microorganism

Abstract

Lactoferrin is an iron-binding protein that is bactericidal against Streptococcus mutans and several other microorganisms. In this study, the influence of several physical conditions as well as the metabolic state of S. mutans on lactoferrin susceptibility were investigated. After exposure to lactoferrin, a 15-min lag period occurred before the initiation of killing, indicating that a two-step process is involved in lactoferrin killing. Cultures harvested during the early exponential phase were very sensitive to lactoferrin, whereas cultures harvested in the early stationary phase were markedly more resistant. The rate of killing was dependent on temperature; there was no loss of viability at 2 degrees C. Killing occurred at pH 5.0 to 6.0 in water and 20 mM glycine, but did not occur at any pH in 50 mM sodium phosphate or N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES) buffer. Addition of exogenous ferrous or ferric ions did not reverse or prevent lactoferrin killing, nor did addition of 1 mM magnesium chloride.

Antibacterial spectrum of lactoferricin B, a potent bactericidal peptide derived from the N‐terminal region of bovine lactoferrin

“…The antimicrobial effectiveness of lactoferricin B was found to be diminished in the presence of certain anions such as HEPES, PIPES, phosphate, citrate or succinate. Our findings are consistent with previous reports indicating that the bactericidal activity of apolactoferrin is reduced in the presence of HEPES, phosphate (Arnold et al 1981), citrate, oxalate or naladixic acid (Lassiter et al 1987). These observations suggest that ionic interactions play an important role in the binding of lactoferricin B and apolactoferrin to lethal target sites on the cell surface.…”

Lactoferrin a multiple bioactive protein: An overview

“…Particular attention should be given to bacteria listed in Table 1 because some of these are known to be resistant to antimicrobials, such as the strains of Staphylococcus aureus, Listeria monocytogenes, methicillin-resistant Klebsiella pneumoniae and Mycobacterium tuberculosis, among others. Lf has also been proven effective against strains of Haemophillus influenzae and Streptococcus mutans that were inhibited by an iron-independent interaction with the cell surface [39,45].…”

Lactoferrin Interaction with Actinobacillus actinomycetemcomitans

“…Binding of bovine lactoferrin to transblotted proteins of cell envelopes of A. actinomycetemcomitans strain ATCC 43718, at different pH-values. Coomassie brilliant blue-stained SDS-PAGE of unheated cell envelope preparation (1) and autoradiographs of blots exposed to '--'^I-bovine lactoferrin at pH 5.0 (2), 6.0 (3), 7.0 (4) and 8.0 (5). Mobilities of molecular size markers are indicated to the left {M^ XlO"*).…”