Killing of Actinobacillus actinomycetemcomitans by human lactoferrin

Antioxidant, anti-inflammatory and antimicrobial activity of natural products in periodontal disease: a comprehensive review

Periodontal diseases (PD) are common chronic inflammatory oral pathologies that are strongly linked to others not found in the mouth cavity. The immune system mediates the host response, which includes the upregulation of proinflammatory cytokines, metalloproteinases, and reactive oxygen species (ROS); the latter may play an important role in the establishment and progression of inflammatory diseases, particularly periodontal disease, via the development of oxidative stress (OS). Natural antioxidants have powerful anti-inflammatory properties, and some can reduce serum levels of key PD indicators such tumor necrosis factor (TNF) and interleukin IL-1. This review compiles, through a thorough literature analysis, the antioxidant, anti-inflammatory, and antibacterial effects of a variety of natural products, as well as their therapeutic potential in the treatment of PD.

Bovine apo-lactoferrin affects the secretion of proteases in Mannheimia haemolytica A2

Mannheimia haemolytica serotype A2 is the main bacterial causative agent of ovine mannheimiosis, a disease that leads to substantial economic losses for livestock farmers. Several virulence factors allow M. haemolytica to colonize the lungs and establish infection. Virulence factors can be directly secreted into the environment by bacteria but are also released through outer membrane vesicles (OMVs). In addition, due to the abuse of antibiotics in the treatment of this disease, multidrug-resistant bacterial strains of M. haemolytica have emerged. One therapeutic alternative to antibiotics or an adjuvant to be used in combination with antibiotics could be lactoferrin (Lf), a multifunctional cationic glycoprotein of the mammalian innate immune system to which no bacterial resistance has been reported. The aim of this work was to determine the effect of bovine iron-free Lf (apo-BLf) on the production and secretion of proteases into culture supernatant (CS) and on their release in OMVs. Zymography assays showed that addition of sub-MIC concentrations of apo-BLf to M. haemolytica cultures inhibited protease secretion without affecting culture growth. Biochemical characterization revealed that these proteases were mainly cysteine- and metalloproteases. The secretion of a 100 kDa metalloprotease was inhibited by sub-MIC concentrations of apo-BLf since this protease was present in the cytoplasm and OMVs but not in CS proteins, as corroborated by Western blotting. On the other hand, proteases produced by M. haemolytica caused cleavage of apo-BLf. However, when Lf is cleaved, peptides known as lactoferricins, which are more bactericidal than natural Lf, can be produced. M. haemolytica A2 protease-mediated degradation of host tissue proteins could be an important virulence factor during the infectious process of pneumonia in ovines. The mechanism of M. haemolytica protease secretion could be inhibited by treatment with apo-BLf in animals.

Diverse Mechanisms of Antimicrobial Activities of Lactoferrins, Lactoferricins, and Other Lactoferrin-Derived Peptides

Lactoferrins are an iron-binding glycoprotein that have important protective roles in the mammalian body through their numerous functions, which include antimicrobial, antitumor, anti-inflammatory, immunomodulatory, and antioxidant activities. Among these, their antimicrobial activity has been the most studied, although the mechanism behind antimicrobial activities remains to be elucidated. Thirty years ago, the first lactoferrin-derived peptide was isolated and showed higher antimicrobial activity than the native lactoferrin lactoferricin. Since then, numerous studies have investigated the antimicrobial potencies of lactoferrins, lactoferricins, and other lactoferrin-derived peptides to better understand their antimicrobial activities at the molecular level. This review defines the current antibacterial, antiviral, antifungal, and antiparasitic activities of lactoferrins, lactoferricins, and lactoferrin-derived peptides. The primary focus is on their different mechanisms of activity against bacteria, viruses, fungi, and parasites. The role of their structure, amino-acid composition, conformation, charge, hydrophobicity, and other factors that affect their mechanisms of antimicrobial activity are also reviewed.

Modification of lactoferrin by peroxynitrite reduces its antibacterial activity and changes protein structure

Lactoferrin (LF) is a multifunctional protein that plays important physiological roles as one of the most concentrated proteins in many human and other mammalian fluids and tissues. In particular, LF provides antibacterial properties to human milk, saliva, and tear fluid. LF also protects against stress-induced lipid peroxidation at inflammation sites through its iron-binding ability. Previous studies have shown that LF can be efficiently nitrated via biologically relevant mediators such as peroxynitrite (ONOO^- ), which are also present at high intracellular concentrations during inflammation and nitrosative stress. Here, we examine changes in antibacterial properties and structure of LF following ONOO^- treatment. The reaction induces nitration of tyrosine and tryptophan residues, which are commonly used as biomarker molecules for several diseases. Treatment with ONOO^- at a 10/1 M ratio of ONOO^- to tyrosine inhibited all antibacterial activity exhibited by native LF. Secondary structural changes in LF were assessed using circular dichroism spectroscopy. Nitration products with and without the addition of Fe³⁺ show significant reduction in alpha-helical properties, suggesting partial protein unfolding. Iron-binding capacity of LF was also reduced after treatment with ONOO^- , suggesting a decreased ability of LF to protect against cellular damage. LC-MS/MS spectrometry was used to identify LF peptide fragments nitrated by ONOO^- , including tyrosine residue Y92 located in the iron-binding region. These results suggest that posttranslational modification of LF by ONOO^- could be an important pathway to exacerbate infection, for example, in inflamed tissues and to reduce the ability of LF to act as an immune responder and decrease oxidative damage.

Oral lactoferrin influences psychological stress in humans: A single-dose administration crossover study

Lactoferrin is a secretory protein with various physiological functions. Bovine lactoferrin has been demonstrated to alleviate psychological stresses in rats, but this effect in humans has not yet been assessed. The present study aimed to investigate the changes in psychological stress markers following a calculation task, with either lactoferrin or a placebo orally administered prior to the task. A total of 16 healthy female college students visited Juntendo University, Inzai, Japan following an overnight fast. Subjects were quietly seated for 15 min to stabilize the respiratory rate at 0.25 Hz (one breath every 4 sec). Then, subjects provided saliva, ingested either lactoferrin (800 mg of lactoferrin + soy milk) or a placebo (soy milk), remained seated for another 15 min with respiration rate at 0.25 Hz, and performed a calculation task. The task comprised two sets of 15-min calculations, with a 5-min interval between sets. Each calculation set consisted of various multiplications and divisions using pairs of three-digit numbers. Following the calculation task, saliva was collected again. Heart rate was also monitored to identify the frequency domain of heart-rate variability. The calculation task resulted in increased activity of salivary amylase, and decreased concentration of chromogranin A for both lactoferrin (P=0.028 and P<0.001, respectively) and placebo (P=0.003 and P<0.001, respectively) treatments. The degrees of changes in these salivary markers were similar between the two treatments. Heart rate variability exhibited an increase in the high-frequency (HF) component (P=0.022) and a decrease in low-frequency (LF)/HF and LF/(LF+HF) ratios (both P<0.001) following the calculation task under the placebo condition, demonstrating an upregulation of parasympathetic and a downregulation of sympathetic nervous activities. These changes in parasympathetic (HF) and sympathetic (LF/HF) activities, however, were alleviated by lactoferrin compared with the placebo (P=0.007 and P=0.026, respectively). Collectively these results suggest that oral lactoferrin may mitigate psychological stress in humans.

Two outer membrane proteins are bovine lactoferrin-binding proteins in Mannheimia haemolytica A1

Mannheimia haemolytica is a Gram negative bacterium that is part of the bovine respiratory disease, which causes important economic losses in the livestock industry. In the present work, the interaction between M. haemolytica A1 and bovine lactoferrin (BLf) was studied. This iron-chelating glycoprotein is part of the mammalian innate-immune system and is present in milk and mucosal secretions; Lf is also contained in neutrophils secondary granules, which release this glycoprotein at infection sites. It was evidenced that M. haemolytica was not able to use iron-charged BLf (BholoLf) as a sole iron source; nevertheless, iron-lacked BLf (BapoLf) showed a bactericidal effect against M. haemolytica with MIC of 4.88 ± 1.88 and 7.31 ± 1.62 μM for M. haemolytica strain F (field isolate) and M. haemolytica strain R (reference strain), respectively. Through overlay assays and 2-D electrophoresis, two OMP of 32.9 and 34.2 kDa with estimated IP of 8.18 and 9.35, respectively, were observed to bind both BapoLf and BholoLf; these OMP were identified by Maldi-Tof as OmpA (heat-modifiable OMP) and a membrane protein (porin). These M. haemolytica BLf binding proteins could be interacting in vivo with both forms of BLf depending on the iron state of the bovine.

A randomized, double-blind, crossover, placebo-controlled clinical trial to assess effects of the single ingestion of a tablet containing lactoferrin, lactoperoxidase, and glucose oxidase on oral malodor

Background

The main components of oral malodor have been identified as volatile sulfur compounds (VSCs) including hydrogen sulfide (H₂S) and methyl mercaptan (CH₃SH). VSCs also play an important role in the progression of periodontal disease. The aim of the present study was to assess the effects of the single ingestion of a tablet containing 20 mg of lactoferrin, 2.6 mg of lactoperoxidase, and 2.6 mg of glucose oxidase on VSCs in the mouth.

Method

Subjects with VSCs greater than the olfactory threshold in their mouth air ingested a test or placebo tablet in two crossover phases. The concentrations of VSCs were monitored at baseline and 10 and 30 min after ingestion of the tablets using portable gas chromatography.

Results

Thirty-nine subjects were included in the efficacy analysis based on a full analysis set (FAS). The concentrations of total VSCs and H₂S at 10 min were significantly lower in the test group than in the placebo group (−0.246 log ng/10 ml [95 % CI −0.395 to −0.098], P = 0.002; −0.349 log ng/10 ml; 95 % CI −0.506 to −0.192; P < 0.001, respectively). In the subgroup analysis, a significant difference in the concentration of total VSCs between the groups was also observed when subjects were fractionated by sex (male or female) and age (20–55 or 56–65 years). The reducing effect on total VSCs positively correlated with the probing pocket depth (P = 0.035).

Conclusions

These results suggest that the ingestion of a tablet containing lactoferrin, lactoperoxidase, and glucose oxidase has suppressive effects on oral malodor.

Trial registration

This trial was registered with the University Hospital Medical Information Network Clinical Trial Registry (number: UMIN000015140, date of registration: 16/09/2014).

Electronic supplementary material

The online version of this article (doi:10.1186/s12903-016-0199-7) contains supplementary material, which is available to authorized users.

Lactoferrin levels in gingival crevicular fluid and saliva of HIV-infected patients with chronic periodontitis

AIM

This study compared lactoferrin (LF) levels in the gingival crevicular fluid (GCF) and saliva between HIV-infected and noninfected patients with chronic periodontitis.

METHODS

For each subject, LF levels were analyzed in one shallow site (SS; PD ≤3 mm), one deep site (DS; PD >5 mm) and in resting whole saliva. Two groups, 28 HIV-infected and 10 noninfected, were selected.

RESULTS

Although the salivary LF levels were higher in HIV-infected than in noninfected individuals, especially in AIDS patients, this was not statistically significant (P > 0.05). Subgingival LF levels for SS and DS were lower among HIV-infected individuals, although AIDS patients showed the lowest levels. Age, smoking, gender, T CD4 lymphocytes levels and viral load did not influence subgingival LF levels, neither for SS nor for DP. Positive fungal culture was observed in 24 HIV-infected patients, but only observed in one in the control group. Overall, LF concentration was significantly higher in DS than SS, both in HIV-infected and noninfected individuals (P < 0.05) and salivary LF levels were always higher than GCF levels.

CONCLUSION

The data indicate that LF levels in the GCF and saliva are not different between HIV-infected and noninfected patients with chronic periodontitis.

Candida biofilm formation on voice prostheses

Laryngopharyngeal malignancy is treated with radiotherapy and/or surgery. When total laryngectomy is required, major laryngeal functions (phonation, airway control, swallowing and coughing) are affected. The insertion of a silicone rubber voice prosthesis in a surgically created tracheoesophageal puncture is the most effective method for voice rehabilitation. Silicone, as is the case with other synthetic materials such as polymethylmethacrylate, polyurethane, polyvinyl chloride, polypropylene and polystyrene, has the propensity to become rapidly colonized by micro-organisms (mainly Candida albicans) forming a biofilm, which leads to the failure of the devices. Silicone is used within voice prosthetic devices because of its flexible properties, which are essential for valve function. Valve failure, as well as compromising speech, may result in aspiration pneumonia, and repeated valve replacement may lead to either tract stenosis or insufficiency. Prevention and control of biofilm formation are therefore crucial for the lifespan of the prosthesis and promotion of tracheoesophageal tissue and lung health. To date, the mechanisms of biofilm formation on voice prostheses are not fully understood. Further studies are therefore required to identify factors influencing Candida biofilm formation. This review describes the factors known to influence biofilm formation on voice prostheses and current strategies employed to prolong their life by interfering with microbial colonization.

In silico investigation of lactoferrin protein characterizations for the prediction of anti-microbial properties

Lactoferrin (Lf) is an iron-binding multi-functional glycoprotein which has numerous physiological functions such as iron transportation, anti-microbial activity and immune response. In this study, different in silico approaches were exploited to investigate Lf protein properties in a number of mammalian species. Results showed that the iron-binding site, DNA and RNA-binding sites, signal peptides and transferrin motifs in the Lf structure were highly conserved. Examined sequences showed three conserved motifs which were repeated twice in the Lf structure, demonstrating ancient duplication events in its gene. Also, results suggest that the functional domains in mammalian Lf proteins are Zinc finger, Tubulin/FtsZ, GTPase, α/β hydrolase and Zinc knuckle. The potential site for nucleic acid binding and the major DNA and RNA- binding sites in this protein were found in the lactoferricin (Lfc) fragment. Due to its high positive charge, Lf is able to bind a large number of compounds. Our analysis also revealed that the interactions between Lf and ITLN1, LYZ, CSN2, and CD14 proteins played an important role in the protective activities of Lf. Analysis for the prediction of secondary structures indicated that high amounts of α-helix, β-strand and β-sheet were present in Lf. The high degree of conservation among mammalian Lf proteins indicates that there is a close relationship between these proteins, reflecting their important role.

A lactotransferrin single nucleotide polymorphism demonstrates biological activity that can reduce susceptibility to caries

Streptococcus mutans is prominently linked to dental caries. Saliva's influence on caries is incompletely understood. Our goal was to identify a salivary protein with anti-S. mutans activity, characterize its genotype, and determine genotypic variants associated with S. mutans activity and reduced caries. An S. mutans affinity column was used to isolate active moieties from saliva obtained from a subject with minimal caries. The bound and eluted protein was identified as lactotransferrin (LTF) by matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) analysis and confirmed by Western blotting with LTF antibody. A single nucleotide polymorphism (SNP) that produced a shift from arginine (R) to lysine (K) at amino acid position 47 in the LTF antimicrobial region (rs: 1126478) killed S. mutans in vitro. Saliva from a subject with moderate caries and with the LTF "wild-type" R form at position 47 had no such activity. A pilot genetic study (n = 30) showed that KK subjects were more likely to have anti-S. mutans activity than RR subjects (P = 0.001; relative risk = 3.6; 95% confidence interval [95% CI] = 1.5 to 11.13). Pretreatment of KK saliva with antibody to LTF reduced S. mutans killing in a dose-dependent manner (P = 0.02). KK subjects were less likely to have caries (P = 0.02). A synthetic 11-mer LTF/K peptide killed S. mutans and other caries-related bacteria, while the LTF/R peptide had no effect (P = 0.01). Our results provide functional evidence that the LTF/K variant results in both anti-S. mutans activity and reduced decay. We suggest that the LTF/K variant can influence oral microbial ecology in general and caries-provoking microbes specifically.

Microbial colonization of Blom-Singer indwelling voice prostheses in laryngectomized patients: a perspective from India

We analyzed a series of adults with an implanted voice prosthesis that had malfunctioned and required removal as a result of the attachment and growth of microorganisms. Our goal was to determine the characteristics of these colonizing microbes. We swabbed the esophageal side of each prosthesis to obtain microbial flora for analysis with standard culture media. In all, we studied 22 prostheses in 18 patients (3 patients had received multiple prostheses). We found mixed contamination (both yeast and bacteria) in 19 of the 22 cultures (86.4%); the other 3 cultures yielded bacteria only, and there was no instance of yeast only. The most common yeast isolated was Candida albicans (68.2% of cultures), and the most common bacterium was Pseudomonas aeruginosa (63.6%). The average lifetime of the prostheses was 201 days (∼6 mo, 3 wk). This study, which was the first of its kind in India, revealed that the microbial picture here was different from that found in previously reported studies of European populations. We presume the differences are attributable to different lifestyles and dietary habits.

Lactoferrin: an alternative view of its role in human biological fluids

Lactoferrin is a major component of biologically important mucosal fluids and of the specific granules of neutrophils. Understanding its biological function is essential for understanding neutrophil- and mucosal-mediated immunity. In this review, we reevaluate the in vivo functions of human lactoferrin (hLF) emphasizing in vivo studies and in vitro studies performed in biologically relevant fluids. We discuss the evidence in the literature that supports (or does not support) proposed roles for hLF in mucosal immunity and in neutrophil function. We argue that the current literature supports a microbiostatic role, but not a microbicidal role, for hLF in vivo. The literature also supports a role for hLF in inhibiting colonization and infection of epithelial surfaces by microorganisms and in protecting tissues from neutrophil-mediated damage. Using this information, we briefly discuss hLF in the context of the complex biological fluids in which it is found.

Lactoferrin a multiple bioactive protein: an overview

BACKGROUND

Lactoferrin (Lf) is an 80kDa iron-binding glycoprotein of the transferrin family. It is abundant in milk and in most biological fluids and is a cell-secreted molecule that bridges innate and adaptive immune function in mammals. Its protective effects range from anticancer, anti-inflammatory and immune modulator activities to antimicrobial activities against a large number of microorganisms. This wide range of activities is made possible by mechanisms of action involving not only the capacity of Lf to bind iron but also interactions of Lf with molecular and cellular components of both hosts and pathogens.

SCOPE OF REVIEW

This review summarizes the activities of Lf, its regulation and potential applications.

MAJOR CONCLUSIONS

The extensive uses of Lf in the treatment of various infectious diseases in animals and humans has been the driving force in Lf research however, a lot of work is required to obtain a better understanding of its activity.

GENERAL SIGNIFICANCE

The large potential applications of Lf have led scientists to develop this nutraceutical protein for use in feed, food and pharmaceutical applications. This article is part of a Special Issue entitled Molecular Mechanisms of Iron Transport and Disorders.

Antimicrobial peptides and periodontal disease

AIMS

The goal of this review is to identify the antimicrobial proteins in the oral fluids, saliva and gingival crevicular fluid and identify functional families and candidates for antibacterial treatment.

RESULTS

Periodontal biofilms initiate a cascade of inflammatory and immune processes that lead to the destruction of gingival tissues and ultimately alveolar bone loss and tooth loss. Treatment of periodontal disease with conventional antibiotics does not appear to be effective in the absence of mechanical debridement. An alternative treatment may be found in antimicrobial peptides and proteins, which can be bactericidal and anti-inflammatory and block the inflammatory effects of bacterial toxins. The peptides have co-evolved with oral bacteria, which have not developed significant peptide resistance. Over 45 antibacterial proteins are found in human saliva and gingival crevicular fluid. The proteins and peptides belong to several different functional families and offer broad protection from invading microbes. Several antimicrobial peptides and proteins (AMPs) serve as templates for the development of therapeutic peptides and peptide mimetics, although to date none have demonstrated efficacy in human trials.

CONCLUSIONS

Existing and newly identified AMPs may be developed for therapeutic use in periodontal disease or can serve as templates for peptide and peptide mimetics with improved therapeutic indices.

Effects of orally administered lactoferrin and lactoperoxidase-containing tablets on clinical and bacteriological profiles in chronic periodontitis patients

This study was undertaken to evaluate the effect of oral administration of lactoferrin (LF) and lactoperoxidase-(LPO-)containing tablet on periodontal condition. Seventy-two individuals with chronic periodontitis were randomly assigned to take either bovine LF and LPO-containing tablets (test group, n = 37) or control tablets (control group, n = 35) every day for 12 weeks. Periodontal parameters and levels of subgingival plaque bacteria, human and bovine LF, and endotoxin in gingival crevicular fluid (GCF) were evaluated at baseline, 1 week, 4 weeks, and 12 weeks. Significant differences were observed in GCF levels of bovine LF between the test and control groups throughout the study (P < .05). However, clinical and bacteriological parameter values proved comparable between the two groups at 1 week to 12 weeks. Therefore, the effect of oral administration of LF and LPO-containing tablets might be weak on periodontal and bacteriological profile in this study.

Serine protease PrtA from Streptococcus pneumoniae plays a role in the killing of S. pneumoniae by apolactoferrin

It is known that apolactoferrin, the iron-free form of human lactoferrin, can kill many species of bacteria, including Streptococcus pneumoniae. Lactoferricin, an N-terminal peptide of apolactoferrin, and fragments of it are even more bactericidal than apolactoferrin. In this study we found that apolactoferrin must be cleaved by a serine protease in order for it to kill pneumococci. The serine protease inhibitors were able to block killing by apolactoferrin but did not block killing by a lactoferrin-derived peptide. Thus, the killing of pneumococci by apolactoferrin appears to require a protease to release a lactoferricin-like peptide(s). Incubation of apolactoferrin with growing pneumococci resulted in a 12-kDa reduction in its molecular mass, of which about 7 to 8 kDa of the reduction was protease dependent. Capsular type 2 and 19F strains with mutations in the gene encoding the major cell wall-associated serine protease, prtA, lost much of their ability to degrade apolactoferrin and were relatively resistant to killing by apolactoferrin (P < 0.001). Recombinant PrtA was also able to cleave apolactoferrin, reducing its mass by about 8 kDa, and greatly enhance the killing activity of the solution containing the apolactoferrin and its cleavage products. Mass spectroscopy revealed that PrtA makes a major cut between amino acids 78 and 79 of human lactoferrin, removing the N-terminal end of the molecule (about 8.6 kDa). The simplest interpretation of these data is that the mechanism by which apolactoferrin kills Streptococcus pneumoniae requires the release of a lactoferricin-like peptide(s) and that it is this peptide(s), and not the intact apolactoferrin, which kills pneumococci.

Short communication: Antimicrobial effect of lactoferrin and its amidated and pepsin-digested derivatives against Salmonella Enteritidis and Pseudomonas fluorescens

The antimicrobial effect of bovine lactoferrin (LF) and its amidated and pepsin-digested derivatives, at concentrations varying from 0.25 to 20 mg/mL, against 3 Salmonella Enteritidis strains and 3 Pseudomonas fluorescens strains was investigated. Lactoferrin showed its maximum antimicrobial effect at 10 mg/mL against the 3 Salmonella strains, with reductions ranging from 1.3 to 2.0 log units, and the 3 Pseudomonas strains, with reductions ranging from 1.8 to 5.4 log units. In the case of amidated LF, the maximum effect on the 3 Salmonella strains was recorded at 0.25 mg/mL, with reductions in the range of 0.8 to 1.2 log units, whereas it was recorded at 1 mg/mL for the 3 Pseudomonas strains, with reductions in the range of 4.4 to 6.0 log units. Pepsin-digested LF showed its maximum antimicrobial effect at 1 mg/mL against the 3 Salmonella strains, with reductions ranging from 2.6 to 3.4 log units, and at 20 mg/mL against the 3 Pseudomonas strains, with reductions ranging from 4.5 to 5.4 log units. It is worth noting the pronounced effect (reductions exceeding 2.5 log units) of a low (1 mg/mL) concentration of pepsin-digested LF, which is naturally formed in the gastrointestinal tract, on Salmonella and Pseudomonas strains. A highly significant inverse correlation was found between capsule polysaccharide levels of bacterial strains and their lethality in the presence of different concentrations of amidated lactoferrin.

Antimicrobial mechanism of action of transferrins: selective inhibition of H+-ATPase

Two bacterial species with different metabolic features, namely, Pseudomonas aeruginosa and Lactococcus lactis, were used as a comparative experimental model to investigate the antimicrobial target and mechanism of transferrins. In anaerobiosis, P. aeruginosa cells were not susceptible to lactoferrin (hLf) or transferrin (hTf). In aerobiosis, the cells were susceptible but O(2) consumption was not modified, indicating that components of the electron transport chain (ETC) were not targeted. However, the respiratory chain inhibitor piericidin A significantly reduced the killing activity of both proteins. Moreover, 2,6-dichlorophenolindophenol (DCIP), a reducing agent that accepts electrons from the ETC coupled to H(+) extrusion, made P. aeruginosa susceptible to hLf and hTf in anaerobiosis. These results indicated that active cooperation of the cell was indispensable for the antimicrobial effect. For L. lactis cells lacking an ETC, the absence of a detectable transmembrane electrical potential in hLf-treated cells suggested a loss of H(+)-ATPase activity. Furthermore, the inhibition of ATPase activity and H(+) translocation (inverted membrane vesicles) provided direct evidence of the ability of hLf to inhibit H(+)-ATPase in L. lactis. Based on these data, we propose that hLf and hTf also inhibit the H(+)-ATPase of respiring P. aeruginosa cells. Such inhibition thereby interferes with reentry of H(+) from the periplasmic space to the cytoplasm, resulting in perturbation of intracellular pH and the transmembrane proton gradient. Consistent with this hypothesis, periplasmic H(+) accumulation was prevented by anaerobiosis or by piericidin A or was induced by DCIP in anaerobiosis. Collectively, these results indicate that transferrins target H(+)-ATPase and interfere with H(+) translocation, yielding a lethal effect in vitro.

Periodontitis, periodontopathic bacteria and lactoferrin

Lactoferrin (LF) is a component of saliva and is suspected to be a defense factor against oral pathogens including Streptococcus mutans and Candida albicans. Periodontitis is a very common oral disease caused by periodontopathic bacteria. Antimicrobial activities and other biological effects of LF against representative periodontopathic bacteria, Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, and Prevotella intermedia, have been widely studied. Association of polymorphisms in LF with incidence of aggressive periodontitis and the role of LF in the gingival crevicular fluid as a marker of periodontitis severity have also been reported. Periodontopathic bacteria reside as a biofilm in supragingival and subgingival plaque. Our recent study indicated that LF exhibits antibacterial activity against planktonic forms of P. gingivalis and P. intermedia at higher concentrations, and furthermore, LF effectively inhibits biofilm formation and reduces the established biofilm of these bacteria at physiological concentrations. A small-scale clinical study indicated that oral administration of bovine LF reduces P. gingivalis and P. intermedia in the subgingival plaque of chronic periodontitis patients. LF seems to be a biofilm inhibitor of periodontopathic bacteria in vitro and in vivo.

Can lactoferrin prevent neonatal sepsis and necrotizing enterocolitis?

Despite the use of potent antimicrobials, neonatal sepsis and necrotizing enterocolitis are associated with significant mortality and morbidity. The emergence of microbial antibiotic resistance is a grave concern. Inflammation secondary to sepsis and necrotizing enterocolitis increases pulmonary and cerebral morbidity. New strategies that target inflammation and reduce the emergence of antibiotic resistance are urgently needed. Lactoferrin has broad-spectrum antimicrobial and immunomodulatory activities. In animal models of colitis, lactoferrin reduces inflammatory injury. Lactoferrin also induces the receptor-mediated proliferation and differentiation of intestinal cells. A randomized, controlled trial of lactoferrin in premature neonates to prevent late-onset sepsis is currently in progress. Lactoferrin is a promising agent in the prevention of neonatal sepsis and necrotizing enterocolitis but needs further evaluation to confirm its safety, tolerability and efficacy.

Inhibitory effects of lactoferrin on growth and biofilm formation of Porphyromonas gingivalis and Prevotella intermedia

Lactoferrin (LF) is an iron-binding antimicrobial protein present in saliva and gingival crevicular fluids, and it is possibly associated with host defense against oral pathogens, including periodontopathic bacteria. In the present study, we evaluated the in vitro effects of LF-related agents on the growth and biofilm formation of two periodontopathic bacteria, Porphyromonas gingivalis and Prevotella intermedia, which reside as biofilms in the subgingival plaque. The planktonic growth of P. gingivalis and P. intermedia was suppressed for up to 5 h by incubation with >or=130 microg/ml of human LF (hLF), iron-free and iron-saturated bovine LF (apo-bLF and holo-bLF, respectively), and >or=6 microg/ml of bLF-derived antimicrobial peptide lactoferricin B (LFcin B); but those effects were weak after 8 h. The biofilm formation of P. gingivalis and P. intermedia over 24 h was effectively inhibited by lower concentrations (>or=8 microg/ml) of various iron-bound forms (the apo, native, and holo forms) of bLF and hLF but not LFcin B. A preformed biofilm of P. gingivalis and P. intermedia was also reduced by incubation with various iron-bound bLFs, hLF, and LFcin B for 5 h. In an examination of the effectiveness of native bLF when it was used in combination with four antibiotics, it was found that treatment with ciprofloxacin, clarithromycin, and minocycline in combination with native bLF for 24 h reduced the amount of a preformed biofilm of P. gingivalis compared with the level of reduction achieved with each agent alone. These results demonstrate the antibiofilm activity of LF with lower iron dependency against P. gingivalis and P. intermedia and the potential usefulness of LF for the prevention and treatment of periodontal diseases and as adjunct therapy for periodontal diseases.

Bactericidal effect of lactoferrin and its amidated and pepsin-digested derivatives on Pseudomonas fluorescens: influence of environmental and physiological factors

The influence of environmental and physiological factors such as substrate composition and inoculum characteristics on the bactericidal activity of bovine lactoferrin (LF) and its amidated and pepsin-digested derivatives against Pseudomonas fluorescens was investigated. Amidated LF (AMILF) exerted the most potent bactericidal activity, with a 5.8-log decrease in P. fluorescens counts, and LF the lowest, with just a 1-log decrease, whereas pepsin-digested LF (PDLF) reduced bacterial counts by 2.7 log, after 1 h at 30 degrees C. Amidation of PDLF increased effectiveness by 1.2 log, whereas pepsin digestion of AMILF decreased effectiveness by 2.8 log. Bactericidal activity of LF and its derivatives was higher in Tris buffer than in phosphate buffer. The bactericidal effect of AMILF and PDLF was enhanced as medium pH was increased from 5.5 to 8.5, whereas LF showed higher activity under acidic or basic conditions than at neutral pH. The presence of cations affected the activity of LF and its derivatives, from a concentration of 10 mM for K+, 1 mM for Na+, and 0.1 mM for Ca2+, Co2+, CU2+, Mg2+, Zn2+, and Fe3+. Bactericidal effectiveness diminished as the bacterial inoculum was increased. Log-phase cultures (10-h incubation) were less sensitive to the bactericidal activity of LF and its derivatives than stationary cultures (20- and 30-h incubation). All these factors should be considered when applications of LF and its derivatives in foods and other complex systems are investigated.

Human recombinant lactoferrin acts synergistically with antimicrobials commonly used in neonatal practice against coagulase-negative staphylococci and Candida albicans causing neonatal sepsis

Neonatal sepsis causes significant mortality and morbidity. Coagulase-negative staphylococci (CoNS) and Candida frequently cause neonatal sepsis at >72 h of age. Lactoferrin, which is present in human milk, is a component of innate immunity and has broad-spectrum antimicrobial activity. The synergistic effects of lactoferrin with antibiotics against neonatal isolates have not been systematically evaluated. Here, eight clinical strains (seven neonatal) of CoNS and three strains (two neonatal) of Candida albicans were studied. MIC50 and MIC90 values of human recombinant lactoferrin (talactoferrin; TLF), vancomycin (VAN) and nafcillin (NAF) against CoNS, and of TLF, amphotericin B (AMB) and fluconazole (FLC) against C. albicans, were evaluated according to established guidelines. Antimicrobial combinations of TLF with NAF or VAN against CoNS, and TLF with AMB or FLC against C. albicans, were evaluated by a checkerboard method with serial twofold dilutions. Synergy was evaluated by the median effects principle, and combination indices and dose reduction indices were reported at 50, 75 and 90% inhibitory effect at several drug-dose ratios. It was found that TLF acted synergistically with NAF and VAN against CoNS, and with AMB and FLC against C. albicans, at multiple dose effects and drug-dose ratios with few exceptions. In synergistic combinations, drug reduction indices indicated a significant reduction in doses of antibiotics, which may be clinically relevant. Thus TLF acts synergistically with anti-staphylococcal and anti-Candida agents commonly used in neonatal practice and is a promising agent that needs to be evaluated in clinical studies.

Evaluation of different iron sources and their influence in biofilm formation by the dental pathogen Actinobacillus actinomycetemcomitans

Actinobacillus actinomycetemcomitans, a pathogen associated with oral and extra-oral infections, requires iron to grow under limiting conditions. Although incapable of producing siderophores, this pathogen could acquire iron by direct interaction with compounds such as haemin, haemoglobin, lactoferrin and transferrin. In this work the ability of different A. actinomycetemcomitans strains to bind and use different iron sources was tested. None of the strains tested used haemoglobin, lactoferrin or transferrin as sole sources of iron. However, all of them used FeCl(3) and haemin as iron sources under chelated conditions. Dot-blot binding assays showed that all strains bind lactoferrin, haemoglobin and haemin, but not transferrin. Insertion inactivation of hmsF, which encodes a predicted cell-envelope protein related to haemin-storage proteins produced by other pathogens, reduced haemin and Congo red binding drastically without affecting haemin utilization as an iron source under chelated conditions. Biofilm assays showed that all strains tested attached to and formed biofilms on plastic under iron-rich and iron-chelated conditions. However, scanning electron microscopy showed that smooth strains formed simpler biofilms than rough isolates. Furthermore, the incubation of rough cells in the presence of FeCl(3) or haemin resulted in the formation of more aggregates and microcolonies compared with the fewer cell aggregates formed when cells were grown in the presence of the synthetic iron chelator dipyridyl. These cell responses to changes in extracellular iron concentrations may reflect those that this pathogen expresses under the conditions it encounters in the human oral cavity.

Perspectives on interactions between lactoferrin and bacteriaThis paper is one of a selection of papers published in this Special Issue, entitled 7th International Conference on Lactoferrin: Structure, Function, and Applications, and has undergone the Journal's usual peer review process

Lactoferrin has long been recognized for its antimicrobial properties, initially attributed primarily to iron sequestration. It has since become apparent that interaction between the host and bacteria is modulated by a complex series of interactions between lactoferrin and bacteria, lactoferrin and bacterial products, and lactoferrin and host cells. The primary focus of this review is the interaction between lactoferrin and bacteria, but interactions with the lactoferrin-derived cationic peptide lactoferricin will also be discussed. We will summarize what is currently known about the interaction between lactoferrin (or lactoferricin) and surface or secreted bacterial components, comment on the potential physiological relevance of the findings, and identify key questions that remain unanswered.

Purification and biochemical characterization of a fibroblast growth factor-binding protein (FGF-BP) from the lactoferrin fraction of bovine milk

By means of gel filtration on a TSK-gel HPLC column in the presence of 8 M urea, a 37-kDa polypeptide (p37) was completely separated from lactoferrin (LF) in the heparin HII fraction of the partially purified LF fraction prepared from bovine milk. Purified p37 was identified as a fibroblast growth factor-binding protein (FGF-BP), since its N-terminal 14 amino acid residues (KKEGRNRRGSKASA) were 100% identical to the corresponding sequence of bovine FGF-BP. It was found, in vitro, that (i) p37 had a higher binding affinity with bFGF than bLF; (ii) p37 functioned as a phosphate acceptor for at least three protein kinases (PKA, CK1 and CK2); (iii) bLF stimulated about 3-fold the PKA-mediated phosphorylation of p37, but suppressed its phosphorylation by CK1; and (iv) galloyl pedunculagin was an effective inhibitor for the phosphorylation of p37 by PKA and CK1. Furthermore, the physiological correlation between p37 and bLF may be regulated through specific phosphorylation of p37 by PKA, since p37 fully phosphorylated by PKA did not bind to bLF in vitro. The sulfatide-induced conformational changes in p37 enabled the phosphorylation of p37 by CK1 and also reduced its ability to bind with bLF in vitro. From these results presented here, it is concluded that (i) p37 (FGF-BP) may be tightly associated with bLF in bovine milk; and (ii) the physiological correlation between p37 and bLF may be regulated by the PKA-mediated full phosphorylation of p37 or by the direct binding of sulfatide to p37 in vivo.

Factors contributing to the potency of antimicrobial cationic peptides from the N-terminal region of human lactoferrin

This study investigated the antimicrobial activities of peptides derived from the N-terminal region of human lactoferrin, and examined the contributions of individual residues to the activity of the most potent peptide. Two regions of antimicrobial activity were identified, the first corresponding to a weakly active peptide, HLP-9, comprising residues 1-9, and a second corresponding to a more potent peptide, HLP-10, comprising residues 18-26 and containing the hexapeptide motif, FQWQRN. Inhibitory studies on peptides from the first region confirm the importance of tryptophan residues in enhancing and broadening peptide activity. Inhibitory studies with glycine-substituted homologues of the more potent peptide showed that F21/G and R25/G substitutions resulted in a major reduction or complete loss of activity, while increased peptide cationicity or flexibility had little effect. Our findings demonstrate that F21 and R25 are critical determinants of potency for HLP-10, and that the second aromatic residue may act synergistically with W23 in developing and enhancing the activity of this cationic peptide.

Lactoferrin and other markers from gingival crevicular fluid and saliva before and after periodontal treatment

OBJECTIVES

The aim of the study was to verify (i) if crevicular fluid defence variables reflect the changes after surgical periodontal treatment and (ii) if they are in correspondence with changes of these variables in the unstimulated and stimulated whole saliva.

MATERIAL AND METHODS

For 12 male and 13 female volunteers with chronic periodontitis lactoferrin concentration as well as the lysozyme and peroxidase activities were determined in crevicular fluid as well as in unstimulated and stimulated saliva before and 14 days after surgical periodontal treatment by a minimal invasive flap technique.

RESULTS

The lactoferrin concentrations decreased significantly in the crevicular fluid eluting solution from 1.63 to 1.23 mg/l reflecting a decrease in the total amount collected, in unstimulated saliva from 10.54 to 8.96 mg/l, and in stimulated saliva from 9.00 to 7.11 mg/l after treatment. No significant change could be found for lysozyme. Peroxidase activity was significantly reduced from 269.06 to 186.15 U/l only in the crevicular fluid.

CONCLUSION

The results of this study suggest that (i) the defence factor lactoferrin is suitable for monitoring of periodontal treatment results and (ii) changes of the lactoferrin concentration in crevicular fluid are related with significant changes in unstimulated and stimulated saliva.

Lactoferrin—a multifunctional protein with antimicrobial properties

Lactoferrin is a member of the transferrin family of iron-binding proteins. Numerous functions have been reported and continue to be reported for the protein, some of which are related to its iron-binding properties. Its extensive antimicrobial activities were originally attributed to its ability to sequester essential iron, however, it is now established that it possesses bactericidal activities as a result of a direct interaction between the protein or lactoferrin-derived peptides. This article reviews the antimicrobial activities of lactoferrin and discusses the potential mode of action of lactoferrin-derived cationic peptides against Gram-negative bacteria in the light of recent studies.

The therapeutic potential of lactoferrin

Lactoferrin (Lf), a natural defence iron-binding protein, is present in exocrine secretions that are commonly exposed to normal flora: milk, tears, nasal exudate, saliva, bronchial mucus, gastrointestinal fluids, cervicovaginal mucus and seminal fluid. Additionally, Lf is produced in polymorphonuclear leukocytes and is deposited by these circulating cells in septic sites. A principal function of Lf is that of scavenging non-protein-bound iron in body fluids and inflamed areas so as to suppress free radical-mediated damage and decrease accessibility of the metal to invading bacterial, fungal and neoplastic cells. Adequate sources of bovine and recombinant human Lf are now available for development of commercial applications. Among the latter are use of Lf in food preservation, fish farming, infant milk formula and oral hygiene. Other readily accessible body compartments for Lf administration include skin, throat and small intestine. Further research is needed for possible medicinal use in colon and systemic tissues. Although Lf is a natural product and should be highly biocompatible, possible hazards have been documented.

Aae, an autotransporter involved in adhesion of Actinobacillus actinomycetemcomitans to epithelial cells

The periodontal pathogen Actinobacillus actinomycetemcomitans possesses myriad virulence factors, among them the ability to adhere to and invade epithelial cells. Recent advances in the molecular manipulation of this pathogen and the sequencing of strain HK 1651 (http://www.genome.ou.edu/act.html) have facilitated examination of the genetics of its interaction with epithelial cells. The related gram-negative organism, Haemophilus influenzae, possesses autotransporter adhesins. A search of the sequence database of strain HK 1651 revealed a homologue with similarity in the pore-forming domain to that of the H. influenzae autotransporter, Hap. A. actinomycetemcomitans mutants deficient in the homologue, Aae, showed reduced binding to epithelial cells. A method for making A. actinomycetemcomitans SUNY 465 transiently resistant to spectinomycin was used with conjugation to generate an isogenic aae mutant. An allelic replacement mutant was created in the naturally transformable A. actinomycetemcomitans strain ATCC 29523. Lactoferrin, an important part of the innate host defense system, protects against bacterial infection by bactericidal and antiadhesion mechanisms. Lactoferrin in human milk removes or cleaves Hap and another autotransporter, an immunoglobulin A1 protease, from the surface of H. influenzae, thereby reducing their binding to epithelial cells. Human milk whey had similar effects on Aae from A. actinomycetemcomitans ATCC 29523 and its binding to epithelial cells; however, there was little effect on the binding of SUNY 465. A difference in the genetic structure of aae in the two strains, apparently due to the copy number of a 135-base repeated sequence, may be the cause of the differential action of lactoferrin. aae is the first A. actinomycetemcomitans gene involved in adhesion to epithelial cells to be identified.

Differences in iron acquisition from human haemoglobin among strains of Actinobacillus actinomycetemcomitans

To get a better insight into the physiology of the high-toxic JP2 clone of Actinobacillus actinomycetemcomitans serotype b, which is strongly associated with juvenile periodontitis in adolescents of African descent, the modes of iron acquisition in this clone were examined and compared to those of other strains of the species. None of the strains examined could utilize human transferrin as a source of iron. This was in accordance with the presence of a non-functional tbpA gene, which normally encodes the A subunit of the transferrin-binding-protein complex. Southern blot analysis indicated that functional duplications of tbpA were not present in the genome. Thus, A. actinomycetemcomitans seems to be in a process of evolution, in which iron acquisition from host transferrin is not essential as in many other members of the pasteurellaceae. All strains could utilize haem as a source of iron. All 11 A. actinomycetemcomitans strains examined harboured a single genomic sequence with homology to the hgpA gene encoding haemoglobin-binding protein A in Haemophilus influenzae. However, in all three strains belonging to the JP2 clone and in one serotype e strain hgpA was a pseudogene. Seven other strains possessed a functional hgpA gene which, according to insertion mutagenesis experiments, was responsible for the ability of these strains to utilize haemoglobin as a source of iron. Thus, the presence of an hgpA pseudogene and the inability to use human haemoglobin as an iron source discriminate the high-toxic JP2 clone from low-toxic serotype b strains and most other strains of A. actinomycetemcomitans.

Lactoferrin iron levels are reduced in saliva of patients with localized aggressive periodontitis

BACKGROUND

Actinobacillus actinomycetemcomitans (Aa) is associated with localized aggressive periodontal disease in juveniles (LAgP). Lactoferrin (LF) is an iron-binding salivary protein that has been shown to kill Aa in its iron-free form (apo) and reduce binding to host cells in its iron-saturated form (halo). However, recent in vitro studies show that LF does not kill clinical isolates of Aa, and LF with reduced levels of bound iron does not interfere with its attachment. These findings suggest that colonization of Aa may occur more readily in an environment containing LF with low iron levels. The purpose of this study was to examine the relationship of LF iron levels in saliva of LAgP patients as compared to their age-, gender-, and race-matched controls.

METHODS

Whole and parotid saliva was collected from LAgP patients and matched controls. Micrograms of LF/mg of protein as well as nanograms of iron/micrograms of LF were determined. Iron binding was determined in parotid saliva by addition of nonlabeled and 59Fe labeled iron.

RESULTS

LAgP patients' whole saliva had higher LF levels than controls, but their LF contained less iron (P < or =0.005). No iron was found in LF from parotid saliva in either group. When iron was added to parotid saliva, the LAgP saliva bound 20 to 30 times less iron than controls (P< or =0.001). Finally, LF was identified as the major iron-binding protein in parotid saliva by 59Fe autoradiography and Western blotting.

CONCLUSIONS

This study shows that the level of bound iron in LF is significantly reduced in LAgP patients compared to controls. These data suggest that LF from LAgP patients has a reduced capacity to bind iron and that LF iron levels may play an important role in Aa-induced LAgP.

Inhibitory effect of synthetic histatin 5 on leukotoxin from Actinobacillus actinomycetemcomitans

Actinobacillus actinomycetemcomitans is a gram-negative bacterium strongly implicated in the pathogenesis of juvenile periodontitis. This periodontal pathogen synthesizes a leukotoxin that destroys human polymorphonuclear leukocytes (PMNs), and this toxin is thought to be responsible for the virulence of A. actinomycetemcomitans. It was therefore of interest to assess whether major virulence factors of periodontal pathogens were neutralized by salivary components. This study focuses on the effect of histatins, components of the nonimmune oral defense system, on leukotoxin activity. Leukotoxin was extracted with polymyxin B from freshly grown anaerobic cultures of A. actinomycetemcomitans strain Y4. PMNs isolated from blood of healthy human volunteers were incubated in a cytotoxicity assay containing PMNs (10(7) cells/ml) and leukotoxin preparation (0-500 microg/ml) in Hanks' balanced salt solution at 37 degrees C for 0-120 min with or without synthetic histatin 5 (0-500 microM). Cytotoxicity was measured by release of lactate dehydrogenase (LDH) at different time intervals. Histatin 5 neutralized the toxic effect of the leukotoxin preparation in a concentration-dependent manner, with an IC(50) value of 150 microM. When PMNs were preincubated with histatin 5 (300 microM), washed and subsequently exposed to leukotoxin, no protective effect was observed. This observation suggests a mechanism of inhibition whereby histatin 5 either directly neutralizes the leukotoxin or interferes with the leukotoxin-PMN interaction. The inhibitory effect of histatin 5 on leukotoxic activity may suggest a new biological function of histatins in the oral cavity as a naturally occurring secondary antibiotic.

Lactoferrin iron levels affect attachment of Actinobacillus actinomycetemcomitans to buccal epithelial cells

BACKGROUND

Prior reports have suggested that the iron-binding protein lactoferrin (LF) may either kill Actinobacillus actinomycetemcomitans (Aa) or interfere with its binding to host cells. Other studies have indicated that the degree of iron saturation of LF might play a role in these interactions. However, these studies utilized strains that had lost critical attachment characteristics found in well-preserved clinical isolates of Aa. The purpose of this work was to study the effect of LF iron levels on survival and attachment of well-preserved clinical isolates of Aa.

METHODS

LF containing 0%, 30%, and 100% iron saturation was tested for its ability to kill clinical isolates of Aa and to inhibit their binding to buccal epithelial cells (BECs).

RESULTS

Neither iron-free LF (apo-LF) nor iron-saturated LF killed Aa clinical isolates. Increasing the iron saturation of LF resulted in an increased inhibition of Aa binding to BECs (P < or =0.005). This effect was consistent for the 3 clinical isolates tested. Pretreatment of Aa with iron-saturated LF reduced binding to BECs by 58%, 61.8%, and 64.2%, respectively, for each of the 3 clinical strains tested (P < or =0.005). Pretreatment of Aa strains with apo-LF, iron alone, or bovine serum albumin had no effect on binding. Pretreatment of BECs with LF (either apo-LF or iron-containing LF) had no influence on Aa binding.

CONCLUSIONS

These results indicate that reduction in binding of Aa to epithelial cells is maximized by pretreatment of Aa cells with iron-saturated lactoferrin. These in vitro results suggest that patients with lactoferrin containing lowered levels of iron would be more susceptible to Aa colonization.

Preliminary observations on influence of dairy products on biofilm removal from silicone rubber voice prostheses in vitro

We determined oropharyngeal biofilm removal from silicone rubber voice prostheses in an artificial throat after perfusion with different commercially available dairy products, including buttermilk, Lactobacillus casei Shirota fermented milk (Yakult, Yakult Netherlands BV, Almere, The Netherlands), low-fat milk, and three types of yogurt. Buttermilk removed both yeasts and bacteria from biofilms on voice prostheses, but this was not observed with a pasteurized buttermilk product. Some of the other products, most notably Yakult fermented milk drink, reduced the number of bacteria, whereas growth of yeasts in the biofilms was not inhibited. This study demonstrates that there may be health benefits associated with the consumption of certain dairy products when applied to the upper digestive tract.

Biofilm formation on voice prostheses: influence of dairy products in vitro

Laryngectomized patients use silicone rubber voice prostheses to regain their speech, however, the lifetime of these devices is limited due to biofilm formation. Following anecdotal evidence, the influence of various dairy products on biofilm formation on voice prostheses was studied, using the artificial throat-model. Biofilms were grown on Groningen and Provox2 voice prostheses by inoculating two artificial throats with the total microflora isolated from an explanted Groningen voice prosthesis. After 3 days, one throat was perfused three times daily with 650 ml dairy product; the other was perfused with phosphate buffered saline, used as a control. After 12 days the microflora on each voice prosthesis was determined. Perfusion of the artificial throat with buttermilk three times daily for 9 days reduced the amount of bacteria and yeasts in the biofilm on Groningen voice prostheses to 3% and 15% of the control, respectively. These effects were not observed with a pasteurized conservable buttermilk product. Yakult fermented milk drink, Mona mild yoghurt, Mona vifit yoghurt, semi-skimmed milk and low-fat yoghurt reduced the amount of bacteria by various degrees, ranging from 12% (Yakult) to 88% (Mona mild) of the control, but these products did not inhibit, and sometimes even stimulated, yeast growth. A combination of buttermilk and Yakult did not show a synergistic effect, as expected. Effects for the Provox2 voice prosthesis were less pronounced. These in vitro experiments in the artificial throat demonstrated that the formation of the biofilm on voice prostheses can be lessened by the daily use of certain dairy products, of which buttermilk had the strongest inhibitory effect, followed by Yakult.

Lactoferrin concentration in milk of bovine clinical mastitis

The lactoferrin (LF) concentration in the milk from dairy cows with clinical mastitis was determined to evaluate the relationship between the LF concentration (LFC) in milk and the non-specific defensive capability of the udder. The mean LFC in 368 milk samples from 319 cows with clinical mastitis was significantly higher (p < 0.01) than that of normal cows. The mean LFC in milk from quarters infected with Mycoplasma bovis or Staphylococcus aureus was significantly higher (p < 0.05) than that of quarters infected with coagulase-negative staphylococci (CNS). In Escherichia coli mastitis, the level of LFC in milk from cows with peracute mastitis was significantly lower (p < 0.01) than that from cows with acute mastitis. In cases of mastitis due to E. coli, the mean LFC in milk from cows that needed more than 10 days to recover from the mastitis or were not cured was significantly lower (p < 0.05) than that for cows which took less than 10 days to be cured. The mean LFC in milk from cows with peracute E. coli mastitis was significantly lower (p < 0.05) than that for cows with mastitis associated with environmental streptococci or CNS, although these low LF levels were somewhat increased after 46 h from the occurrence of mastitis. These results suggest that the decreased levels of LF in peracute E. coli mastitis may be associated with the progress of inflammation in the early phase of mastitis.