Bacteria-binding plasma proteins in pellicles formed on hydroxyapatite in vitro and on teeth in vivo

Effect of Processing Methods of Human Saliva on the Proteomic Profile and Protein-Mediated Biological Processes

The use of saliva as a protein source prior to microbiological and biological assays requires previous processing. However, the effect of these processing methods on the proteomic profile of saliva has not been tested. Stimulated human saliva was collected from eight healthy volunteers. Non-processed saliva was compared with 0.22 μm filtered, 0.45 μm filtered, and pasteurized saliva, by liquid chromatography-mass spectrometry. Data are available via ProteomeXchange with identifier PXD039248. The effect of processed saliva on microbial adhesion was tested using bacterial and fungus species and in biological cell behavior using HaCaT immortalized human keratinocytes. Two hundred and seventy-eight proteins were identified in non-processed saliva, of which 54 proteins (≈19%) were exclusive. Saliva processing reduced identified proteins to 222 (≈80%) for the 0.22 μm group, 219 (≈79%) for the 0.45 μm group, and 201 (≈72%) for the pasteurized saliva, compared to non-processed saliva. The proteomic profile showed similar molecular functions and biological processes. The different saliva processing methods did not alter microbial adhesion (ANOVA, p > 0.05). Interestingly, pasteurized saliva reduced keratinocyte cell viability. Saliva processing methods tested reduced the proteomic profile diversity of saliva but maintained similar molecular functions and biological processes, not interfering with microbial adhesion and cell viability, except for pasteurization, which reduced cell viability.

The Impact of Early Saliva Interaction on Dental Implants and Biomaterials for Oral Regeneration: An Overview

The presence of saliva in the oral environment is relevant for several essential health processes. However, the noncontrolled early saliva interaction with biomaterials manufactured for oral rehabilitation may generate alterations in the superficial properties causing negative biological outcomes. Therefore, the present review aimed to provide a compilation of all possible physical-chemical-biological changes caused by the early saliva interaction in dental implants and materials for oral regeneration. Dental implants, bone substitutes and membranes in dentistry possess different properties focused on improving the healing process when in contact with oral tissues. The early saliva interaction was shown to impair some positive features present in biomaterials related to quick cellular adhesion and proliferation, such as surface hydrophilicity, cellular viability and antibacterial properties. Moreover, biomaterials that interacted with contaminated saliva containing specific bacteria demonstrated favorable conditions for increased bacterial metabolism. Additionally, the quantity of investigations associating biomaterials with early saliva interaction is still scarce in the current literature and requires clarification to prevent clinical failures. Therefore, clinically, controlling saliva exposure to sites involving the application of biomaterials must be prioritized in order to reduce impairment in important biomaterial properties developed for rapid healing.

Functional biomedical materials derived from proteins in the acquired salivary pellicle

In the oral environment, the acquired salivary pellicle (ASP) on the tooth surface comprises proteins, glycoproteins, carbohydrates, and lipids. The ASP can specifically and rapidly adsorb on the enamel surface to provide effective lubrication, protection, hydration, and remineralisation, as well as be recognised by various bacteria to form a microbial biofilm (plaque). The involved proteins, particularly various phosphoproteins such as statherins, histatins, and proline-rich proteins, are vital to their specific functions. This review first describes the relationship between the biological functions of these proteins and their structures. Subsequently, recent advances in functional biomedical materials derived from these proteins are reviewed in terms of dental/bone therapeutic materials, antibacterial materials, tissue engineering materials, and coatings for medical devices. Finally, perspectives and challenges regarding the rational design and biomedical applications of ASP-derived materials are discussed.

Effect of nonionic and amphoteric surfactants on salivary pellicles reconstituted in vitro

Surfactants are important components of oral care products. Sodium dodecyl sulfate (SDS) is the most common because of its foaming properties, taste and low cost. However, the use of ionic surfactants, especially SDS, is related to several oral mucosa conditions. Thus, there is a high interest in using non-ionic and amphoteric surfactants as they are less irritant. To better understand the performance of these surfactants in oral care products, we investigated their interaction with salivary pellicles i.e., the proteinaceous films that cover surfaces exposed to saliva. Specifically, we focused on pentaethylene glycol monododecyl ether (C12E5) and cocamidopropyl betaine (CAPB) as model nonionic and amphoteric surfactants respectively, and investigated their interaction with reconstituted salivary pellicles with various surface techniques: Quartz Crystal Microbalance with Dissipation, Ellipsometry, Force Spectroscopy and Neutron Reflectometry. Both C12E5 and CAPB were gentler on pellicles than SDS, removing a lower amount. However, their interaction with pellicles differed. Our work indicates that CAPB would mainly interact with the mucin components of pellicles, leading to collapse and dehydration. In contrast, exposure to C12E5 had a minimal effect on the pellicles, mainly resulting in the replacement/solubilisation of some of the components anchoring pellicles to their substrate.

Proteomic profile of the saliva and plasma protein layer adsorbed on Ti-Zr alloy: the effect of sandblasted and acid-etched surface treatment

Titanium-zirconium (Ti-Zr) alloy has been widely used as a biomaterial for implant devices, and it is commonly treated by sandblasting followed by acid etching (SLA) to improve biological responses. Although protein adsorption is the first biological response, the effect of this SLA treatment on the proteomic profile of proteins adsorbed from saliva and blood plasma has not been tested. In this study, the proteomic profile was evaluated by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). Streptococcus sanguinis was used to test whether the protein layer affects bacterial adhesion. SLA treatment affected the proteomic profile, showing exclusive proteins adsorbed from saliva (14) and plasma (3). However, both groups exhibited close patterns of intensity for common proteins, molecular functions and biological processes mediated by proteins. Interestingly, Ti-Zr_SLA showed higher bacterial adhesion (∼1.9 fold over) for the surface coated with plasma proteins. Therefore, SLA treatment of Ti-Zr alloy changed the proteomic profile, which may affect bacterial adhesion.

The influence of surface texture and wettability on initial bacterial adhesion on titanium and zirconium oxide dental implants

BACKGROUND

This study aims to investigate bacterial adhesion on different titanium and ceramic implant surfaces, to correlate these findings with surface roughness and surface hydrophobicity, and to define the predominant factor for bacterial adhesion for each material.

METHODS

Zirconia and titanium specimens with different surface textures and wettability (5.0 mm in diameter, 1.0 mm in height) were prepared. Surface roughness was measured by perthometer (R _a ) and atomic force microscopy, and hydrophobicity according to contact angles by computerized image analysis. Bacterial suspensions of Streptococcus sanguinis and Staphylococcus epidermidis were incubated for 2 h at 37 °C with ten test specimens for each material group and quantified with fluorescence dye CytoX-Violet and an automated multi-detection reader.

RESULTS

Variations in surface roughness (R _a ) did not lead to any differences in adhering S. epidermidis, but higher R _a resulted in increased S. sanguinis adhesion. In contrast, higher bacterial adhesion was observed on hydrophobic surfaces than on hydrophilic surfaces for S. epidermidis but not for S. sanguinis. The potential to adhere S. sanguinis was significantly higher on ceramic surfaces than on titanium surfaces; no such preference could be found for S. epidermidis.

CONCLUSIONS

Both surface roughness and wettability may influence the adhesion properties of bacteria on biomaterials; in this context, the predominant factor is dependent on the bacterial species. Wettability was the predominant factor for S. epidermidis and surface texture for S. sanguinis. Zirconia did not show any lower bacterial colonization potential than titanium. Arithmetical mean roughness values R _a (measured by stylus profilometer) are inadequate for describing surface roughness with regard to its potential influence on microbial adhesion.

Saliva and Serum Protein Exchange at the Tooth Enamel Surface

The acquired enamel pellicle is an oral, fluid-derived protein layer that forms on the tooth surface. It is a biologically and clinically important integument that protects teeth against enamel demineralization, and abrasion. Tooth surfaces are exposed to different proteinaceous microenvironments depending on the enamel location. For instance, tooth surfaces close to the gingival sulcus contact serum proteins that emanate via this sulcus, which may impact pellicle composition locally. The aims of this study were to define the major salivary and serum components that adsorb to hydroxyapatite, to study competition among them, and to obtain preliminary evidence in an in vivo saliva/serum pellicle model. Hydroxyapatite powder was incubated with saliva and serum, and the proteins that adsorbed were identified by mass spectrometry. To study competition, saliva and serum proteins were labeled with CyDyes, mixed in various proportions, and incubated with hydroxyapatite. In vivo competition was assessed using a split-mouth design, with half the buccal tooth surfaces coated with serum and the other half with saliva. After exposure to the oral environment for 0 min, 30 min and 2 h, the pellicles were analyzed by SDS-PAGE. In pure saliva- or serum-derived pellicles, 82 and 84 proteins were identified, respectively. When present concomitantly, salivary protein adsorbers effectively competed with serum protein adsorbers for the hydroxyapatite surface. Specifically, acidic proline-rich protein, cystatin, statherin and protein S100-A9 proteins competed off apolipoproteins, complement C4-A, haptoglobin, transthyretin and serotransferrin. In vivo evidence further supported the replacement of serum proteins by salivary proteins. In conclusion, although significant numbers of serum proteins emanate from the gingival sulcus, their ability to participate in dental pellicle formation is likely reduced in the presence of strong salivary protein adsorbers. The functional properties of the acquired enamel pellicle will therefore be mostly dictated by the salivary component.

Adhesion of Porphyromonas gingivalis and Tannerella forsythia to dentin and titanium with sandblasted and acid etched surface coated with serum and serum proteins - An in vitro study

OBJECTIVE

To evaluate the adhesion of selected bacterial strains incl. expression of important virulence factors at dentin and titanium SLA surfaces coated with layers of serum proteins.

METHODS

Dentin- and moderately rough SLA titanium-discs were coated overnight with human serum, or IgG, or human serum albumin (HSA). Thereafter, Porphyromonas gingivalis, Tannerella forsythia, or a six-species mixture were added for 4h and 24h. The number of adhered bacteria (colony forming units; CFU) was determined. Arg-gingipain activity of P. gingivalis and mRNA expressions of P. gingivalis and T. forsythia proteases and T. forsythia protease inhibitor were measured.

RESULTS

Coating specimens never resulted in differences exceeding 1.1 log10 CFU, comparing to controls, irrespective the substrate. Counts of T. forsythia were statistically significantly higher at titanium than dentin, the difference was up to 3.7 log10 CFU after 24h (p=0.002). No statistically significant variation regarding adhesion of the mixed culture was detected between surfaces or among coatings. Arg-gingipain activity of P. gingivalis was associated with log10 CFU but not with the surface or the coating. Titanium negatively influenced mRNA expression of T. forsythia protease inhibitor at 24h (p=0.026 uncoated, p=0.009 with serum).

CONCLUSIONS

The present findings indicate that: a) single bacterial species (T. forsythia) can adhere more readily to titanium SLA than to dentin, b) low expression of T. forsythia protease inhibitor may influence the virulence of the species on titanium SLA surfaces in comparison with teeth, and c) surface properties (e.g. material and/or protein layers) do not appear to significantly influence multi-species adhesion.

Novel protein-repellent and biofilm-repellent orthodontic cement containing 2-methacryloyloxyethyl phosphorylcholine

The objectives of this study were to develop the first protein-repellent resin-modified glass ionomer cement (RMGI) by incorporating 2-methacryloyloxyethyl phosphorylcholine (MPC) for orthodontic applications, and to investigate the MPC effects on protein adsorption, biofilm growth, and enamel bond strength. MPC was incorporated into RMGI at 0% (control), 1.5%, 3%, and 5% by mass. Specimens were stored in water at 37°C for 1 and 30 days. Enamel shear bond strength (SBS) was measured, and the adhesive remnant index (ARI) scores were assessed. Protein adsorption onto the specimens was determined by a micro bicinchoninic acid method. A dental plaque microcosm biofilm model with human saliva as inoculum was used. The results showed that adding 3% of MPC into RMGI did not significantly reduce the SBS (p > 0.1). There was no significant loss in SBS for RMGI containing 3% MPC after water-aging for 30 days, as compared to 1 day (p > 0.1). RMGI with 3% MPC had protein adsorption that was 1/10 that of control. RMGI with 3% MPC greatly reduced the bacterial adhesion, and lactic acid production and colony-forming units of biofilms, while substantially increasing the medium solution pH containing biofilms. The protein-repellent and biofilm-repellent effects were not decreased after water-aging for 30 days. In conclusion, the MPC-containing RMGI is promising to reduce biofilms and white spot lesions without compromising orthodontic bracket-enamel bond strength. The novel protein-repellent method may have applicability to other orthodontic cements, dental composites, adhesives, sealants, and cements to repel proteins and biofilms. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 949-959, 2016.

Influence of substratum hydrophobicity on salivary pellicles: organization or composition?

Different physico-chemical properties (eg adsorption kinetics, thickness, viscoelasticity, and mechanical stability) of adsorbed salivary pellicles depend on different factors, including the properties (eg charge, roughness, wettability, and surface chemistry) of the substratum. Whether these differences in the physico-chemical properties are a result of differences in the composition or in the organization of the pellicles is not known. In this work, the influence of substratum wettability on the composition of the pellicle was studied. For this purpose, pellicles eluted from substrata of different but well-characterized wettabilities were examined by means of sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). The results showed that substratum hydrophobicity did not have a major impact on pellicle composition. In all substrata, the major pellicle components were found to be cystatins, amylases and large glycoproteins, presumably mucins. In turn, interpretation of previously reported data based on the present results suggests that variations in substratum wettability mostly affect the organization of the pellicle components.

In vitro activity of Carvacrol against titanium-adherent oral biofilms and planktonic cultures

OBJECTIVE

The aim of this study was to test the effect of Carvacrol against oral pathogens and their preformed biofilms on titanium disc surface.

METHODS

Minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and biofilm inhibitory concentration (BIC) were performed to evaluate Carvacrol antibacterial activity, while flow cytometry (FCM) was used to verify the Carvacrol effect on esterase activity and membrane permeability. Carvacrol was tested in vitro on single- and multi-species biofilms formed on titanium disc by Streptococcus mutans ATCC 25175, Porphyromonas gingivalis ATCC 33277 or Fusobacterium nucleatum ATCC 25586, in different combinations, comparing its effect to that of chlorhexidine.

RESULTS

The pathogens were sensitive to Carvacrol with MICs and MBCs values of 0.25 % and 0.50 % and BICs of 0.5 % for S. mutans ATCC 25175 and 1 % for P. gingivalis ATCC 33277 and F. nucleatum ATCC 25586. FCM analysis showed that treatment of planktonic cultures with Carvacrol caused an increase of damaged cells and a decrement of bacteria with active esterase activity. Moreover, Carvacrol demonstrated greater biofilm formation preventive property compared to chlorhexidine against titanium-adherent single- and multi-specie biofilms, with statistically significant values.

CONCLUSIONS

Carvacrol showed inhibitory activity against the tested oral pathogens and biofilm formation preventive property on their oral biofilm; then, it could be utilized to control and prevent the colonization of microorganisms with particular significance in human oral diseases.

CLINICAL RELEVANCE

This natural compound may be proposed in daily hygiene formulations or as an alternative agent supporting traditional antimicrobial protocols to prevent periodontal diseases in implanted patients.

Pellicle and early dental plaque in periodontitis patients before and after surgical pocket elimination

OBJECTIVE

Gingival inflammation may affect the composition of the dental pellicle and initial acquisition of bacteria, which in turn could affect the healing of the periodontal pocket. The aim of this study was to examine the dental pellicle and early supragingival biofilms in periodontitis patients with an established subgingival infiltrate before and after surgical pocket elimination.

MATERIALS AND METHODS

Eleven patients with remaining pockets were selected. Samples were taken before and after surgical pocket elimination and after subsequent experimental gingivitis. Pellicle proteins were analyzed by SDS-PAGE, immunoblotting and image analysis and 4-h supragingival plaque by culturing.

RESULTS

The inflammatory status affected to a greater extent the concentration of plasma proteins than salivary proteins in the dental pellicle. The highest plasma protein concentrations were observed at remaining periodontal pockets where also the highest bacterial counts were found. The TVC was reduced on the gingival tooth surfaces (p < 0.05) after pocket elimination and increased slightly during experimental gingivitis. The finding of streptococci was highest on the incisal tooth surfaces and increased after surgery. Gram-negative anaerobes were sparse but seen more often before than after pocket elimination and on gingival than on incisal surfaces.

CONCLUSIONS

This study suggests that increased amounts of plasma proteins in the pellicle formed in the presence of remaining periodontal pockets may foster the acquisition of bacteria, including proteolytic Gram-negative species. This, in turn, results in an increased de novo plaque formation rate.

NanoWear of Salivary Films vs. Substratum Wettability

The pellicle serves as a multifunctional protective layer, providing, e.g., lubrication and remineralization and also acting as a diffusion barrier. In addition, since the formation of the pellicle precedes the adhesion of micro-organisms, it is also important as a conditioning film. We present a novel approach to study the influence of the water wettability of solid surfaces on the strength of adsorbed salivary films. It is based on studying the wear resistance of the films with an atomic force microscope operated in the friction force spectroscopy mode. This methodology provides the strength of the films in terms of the forces needed for breaking and removing them. Our results indicate that these forces are highly dependent on the water wettability of the underlying substrata, decreasing with increasing hydrophobicity. Thus, this study provides valuable information for the design of materials exposed in the oral cavity, i.e., materials that will minimize plaque formation and be easy to clean.

A comprehensive method for determination of fatty acids in the initial oral biofilm (pellicle)

The acquired pellicle is a tenacious organic layer covering the surface of teeth, protecting the underlying dental hard tissues. Lipids account for about one quarter of the pellicle's dry weight and are assumed to be of considerable importance for their protective properties. Nevertheless, only preliminary information is available about the nature of lipids in the pellicle. Gas chromatography coupled with electron impact ionization mass spectrometry was used to establish a convenient analytical protocol in order to obtain a qualitative and quantitative characterization of a wide range of FAs (C(12)-C(22)). In situ biofilm formation was performed on bovine enamel slabs mounted on individual splints carried by 10 subjects. A modified Folch extraction procedure was adopted to extract the lipids from the detached pellicle, followed by transesterification to fatty acid methyl esters using methanol and concentrated hydrochloric acid. Tridecanoic and nonadecanoic acid were used as internal standards suitable and reliable for robust, precise and accurate measurements. The present study demonstrates, for the first time, a procedure based on a combination of innovative specimen generation and convenient sample preparation with sensitive GC-MS analysis for the determination of the fatty acid profile of the initial oral biofilm.

Adhesion of Porphyromonas gingivalis and Biofilm Formation on Different Types of Orthodontic Brackets

Objectives. To examine the interaction between Porphyromonas gingivalis and 3 different orthodontic brackets in vitro, focusing on the effect of an early salivary pellicle and other bacteria on the formation of biofilms. Material and Methods. Mono- and multi-species P. gingivalis biofilms were allowed to form in vitro, on 3 different bracket types (stainless steel, ceramic and plastic) with and without an early salivary pellicle. The brackets were anaerobically incubated for 3 days in Brain Heart Infusion Broth to form biofilms. Bacteria were quantified by trypsin treatment and enumeration of the total viable counts of bacteria recovered. Results. Saliva was found to significantly affect (P < 0.001) adhesion and biofilm formation of P. gingivalis, with higher numbers for the coated brackets. No significant effect was detected for the impact of the type of biofilm, although on stainless steel and plastic brackets there was a tendency for higher numbers of the pathogen in multi-species biofilms. Bracket material alone was not found to affect the number of bacteria. Conclusions. The salivary pellicle seems to facilitate the adhesion of P. gingivalis and biofilm formation on orthodontic brackets, while the material comprising the brackets does not significantly impact on the number of bacteria.

Protein adhesion on dental surfaces-a combined surface analytical approach

Protein adsorption is a field of huge interest in a number of application fields. Information on protein adhesion is accessible by a variety of methods. However, the results obtained are significantly influenced by the applied technique. The objective of this work was to understand the role of adhesion forces (obtained by scanning force spectroscopy, SFS) in the process of protein adsorption and desorption. In SFS, the protein is forced to and retracted from the surface, even under unfavorable conditions, in contrast to the natural situation. Furthermore, adhesion forces are correlated with adhesion energies, neglecting the entropic part in the Gibbs enthalpy. In this context, dynamic contact angle (DCA) measurements were performed to identify the potential of this method to complement SFS data. In DCA measurements, the protein diffuses voluntarily to the surface and information on surface coverage and reversibility of adsorption is obtained, including entropic effects (conformational changes and hydrophobic effect). It could be shown that the surface coverage (by DCA) of bovine serum albumin on dental materials correlates well with the adhesion forces (by SFS) if no hydrophobic surface is involved. On those, the entropic hydrophobic effect plays a major role. As a second task, the reversibility of the protein adsorption, i.e., the voluntary desorption as studied by DCA, was compared to the adhesion forces. Here, a correlation between low adhesion forces and good reversibility could be found as long as no covalent bonds were involved. The comparative study of DCA and SFS, thus, leads to a more detailed picture of the complete adsorption/desorption cycle.

Bacteriophage lysin mediates the binding of streptococcus mitis to human platelets through interaction with fibrinogen

The binding of bacteria to human platelets is a likely central mechanism in the pathogenesis of infective endocarditis. We have previously found that platelet binding by Streptococcus mitis SF100 is mediated by surface components encoded by a lysogenic bacteriophage, SM1. We now demonstrate that SM1-encoded lysin contributes to platelet binding via its direct interaction with fibrinogen. Far Western blotting of platelets revealed that fibrinogen was the major membrane-associated protein bound by lysin. Analysis of lysin binding with purified fibrinogen in vitro confirmed that these proteins could bind directly, and that this interaction was both saturable and inhibitable. Lysin bound both the Aα and Bβ chains of fibrinogen, but not the γ subunit. Binding of lysin to the Bβ chain was further localized to a region within the fibrinogen D fragment. Disruption of the SF100 lysin gene resulted in an 83±3.1% reduction (mean ± SD) in binding to immobilized fibrinogen by this mutant strain (PS1006). Preincubation of this isogenic mutant with purified lysin restored fibrinogen binding to wild type levels. When tested in a co-infection model of endocarditis, loss of lysin expression resulted in a significant reduction in virulence, as measured by achievable bacterial densities (CFU/g) within vegetations, kidneys, and spleens. These results indicate that bacteriophage-encoded lysin is a multifunctional protein, representing a new class of fibrinogen-binding proteins. Lysin appears to be cell wall-associated through its interaction with choline. Once on the bacterial surface, lysin can bind fibrinogen directly, which appears to be an important interaction for the pathogenesis of endocarditis.

The binding of bacteria to human platelets is thought to be a central event in the development of endocarditis (a life-threatening cardiovascular infection). We have previously found that platelet binding by Streptococcus mitis is mediated by surface components encoded by a bacteriophage contained within the host bacterium. We now show that lysin (an enzyme of bacteriophage origin) contributes to platelet binding via its direct interaction with fibrinogen on the platelet surface. Lysin bound to purified fibrinogen in vitro, and this interaction specifically involved the Aα and Bβ chains of fibrinogen. Binding of lysin to the Bβ chain was further localized to a region within the fibrinogen D fragment. Disruption of the gene encoding lysin gene resulted in a significant reduction in binding to fibrinogen by S. mitis, as well as a major reduction in virulence, as measured by a rat model of endocarditis. These results indicate that lysin is a multifunctional protein, representing a new class of fibrinogen-binding molecules. Lysin is localized to the bacterial surface via its interaction with cell wall choline, where it then can bind fibrinogen directly. Cell surface lysin apparently also contributes to the development of endovascular infections via its previously unrecognized fibrinogen binding activity.

Production from dairy cows of semi-industrial quantities of milk-protein concentrate (MPC) containing efficacious anti-Candida albicans IgA antibodies

Bovine milk antibodies directed against human pathogenic organisms have potential as prophylactic or therapeutic treatments of disorders affecting mucosal surfaces. The cow, however, does not naturally secrete high levels of IgA in milk, the predominant immunoglobulin of the mucosal immune system. We have patented an immunisation protocol that results in increased production of IgA in ruminant milk and in this study established that our protocol can be used on a scale sufficient to produce semi-industrial quantities of milk for processing. Cows were immunised with a common pathogenic yeast, Candida albicans and responded with high levels of antigen-specific IgA antibodies in their milk. The spray-dried milk-protein concentrate (85% protein) powder was shown to reduce adherence of Cand. albicans cells in in vitro adherence assays, demonstrating an ability to retain efficacy through the processing. These results suggest that this milk product may be of therapeutic value if the reduction in Cand. albicans adhesion observed in vitro translates to reduced colonisation in vivo.

Identification of protein components in in vivo human acquired enamel pellicle using LC-ESI-MS/MS

The acquired enamel pellicle is a thin protein film forming upon exposure of tooth enamel surfaces to saliva. The structural analysis of this integument relies on efficient pellicle harvesting and protein identification procedures. Material from three individual subjects and two pooled samples yielded the identification by LC-ESI-MS/MS of 130 pellicle proteins of which 89 were found in three or more experiments. A high intersubject consistency in pellicle composition was observed.

Oral adhesion and survival of probiotic and other lactobacilli and bifidobacteria in vitro

INTRODUCTION

Most probiotic products are consumed orally and hence it is feasible that the bacteria in these products may also attach to oral surfaces; however, the effects of these bacteria on the oral ecosystem are mostly unknown. Our aim was to evaluate the oral colonization potential of different probiotic, dairy, and fecal Lactobacillus and Bifidobacterium strains in vitro.

METHODS

The binding of 17 Lactobacillus and seven Bifidobacterium strains to hydroxyapatite and microtitre wells coated with human saliva was tested. Binding of selected strains to human buccal epithelial cells and co-adherence with Fusobacterium nucleatum were also investigated. In addition, the survival in sterilized human whole saliva was examined.

RESULTS

There was a large variation in binding to saliva-coated surfaces and buccal epithelial cells but all strains survived in saliva. The binding pattern of the probiotics did not differ from the binding of the fecal strains. F. nucleatum altered the binding of both the low-binding bifidobacteria and the high-binding lactobacilli.

CONCLUSION

The differences in binding in vitro may indicate that there are also differences in the persistence of the different probiotic strains in the oral cavity in vivo.

Candida albicans binds to saliva proteins selectively adsorbed to silicone

Explanted voice prostheses obtained from 5 patients at the time of prosthesis replacement were consistently colonized by yeast, in particular Candida albicans. A simple, reproducible, in vitro model of C. albicans adherence to saliva-coated voice prosthesis silicone was developed. Whole saliva promoted adherence of C. albicans to silicone in a dose-dependent manner. Saliva rinses from voice prosthesis patients also promoted binding of C. albicans to silicone in vitro (mean adherence 14.9% +/- 2.8% of input C. albicans cells). This was significantly higher than C. albicans adherence to silicone in the absence of saliva (P < .001) or adherence promoted by saliva rinses from healthy volunteers (P < .005). Polyacrylamide gel electrophoresis analysis and a blot overlay adherence assay revealed that certain salivary proteins were selectively adsorbed to silicone and that C. albicans yeast cells adhered specifically to the adsorbed salivary proteins.

Characterization of two Candida albicans surface mannoprotein adhesins that bind immobilized saliva components

Salivary components, including the basic proline-rich proteins (bPRP), act as receptors for the adherence of Candida albicans, and this interaction may be important for oral colonization and the development of mucosal Candida infections. Treatment of C. albicans cells with agents affecting either proteinacious or carbohydrate surface macromolecules reduced their adherence in in vitro assays of C. albicans adherence to saliva-coated hydroxyapatite beads and to membrane-immobilized salivary bPRP. In order to identify C. albicans adhesins that bind saliva receptors, yeast cell surface material was extracted by mild glucanase treatment, and was shown to competitively inhibit ( > 50%) the adherence of C. albicans yeast cells in both assays. Concanavalin A sepharose affinity chromatography was used to partially purify glycosylated components of the extract, and two polypeptides (97.4 and 35 kDa) were further purified by preparative SDS PAGE separation and electro-elution. The 97.4 and 35 kDa polypetides each possessed greater adherence-inhibitory specific activity (> 100-fold and > 30-fold respectively) than the original glucanase extract from C. albicans yeast cells. The 35 kDa putative surface protein was identified by N-terminal sequencing and immunoblotting, as the 1,3-beta glucosyltransferase, Bgl2p.