Combined Bactericidal Effect of Human Lactoferrin and Lysozyme Against<i>Streptococcus mutans</i>serotype c

Abstract

We have studied the antibacterial effect of human lactoferrin and lysozyme (LZ), separately and together, on the viability of Streptococcus mutans , serotype c, in vitro . Both proteins were purified from human colostrum and lactoferrin was used in iron-free (apo LF), Fe 3+ -saturated (sat LF), and partly saturated (LF) forms. In incubation experiments at pH 5.5, both LZ and apo LF at physiological human salivary concentrations (25-50 mg/l) inhibited streptococcal viability in a time- and dose-dependent way. In all experiments LF and sat LF were clearly least effective. Interestingly, LZ and apo LF together displayed an enhanced bactericidal activity against S. mutans (serotype c), whereas a combination of sat LF and LZ did not have such an effect. This is a new finding to the previously described interactions between innate antimicrobial agents against cariogenic bacteria. An understanding of these interactions may be important in engineering approaches to selectively control specific oral bacteria, such as mutans streptococci. Keywords: Streptococcus mutans ; Lactoferrin; Lysozyme; Antimicrobial factors; Saliva.