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Coadhesion between oral microbial pairs is an established factor in the spatiotemporal development and prevalence of mixed-species communities in early dental plaque in vivo. This study compares removal and de novo adhesion of pairs of coadhering and non-coadhering oral actinomyces and streptococci by sonic brushing on salivary pellicles in a non-contact mode as a function of the distance between the brush and the pellicle surface in vitro. First, actinomycetes were adhered to a pellicle surface, after which streptococci suspended in saliva were allowed to adhere. Removal was examined by non-contact, sonic brushing with a wetted brush on a either a wetted or a substratum immersed to a depth of 7 mm. After brushing, de novo adhesion of streptococci to brushed pellicles was studied. For coadhering and non-coadhering pairs, 34% and 9%, respectively, of the adhering bacteria were involved in aggregates comprising more than 10 organisms. Non-contact, sonic brushing removed up to 99% of the adhering bacteria, regardless of the state of immersion of the substratum. Bacterial removal decreased with increasing distance of up to 6 mm between brush and pellicle surface. For the non-coadhering pair, subsequent exposure of pellicles to a streptococcal suspension yielded about 6% of bacteria involved in large aggregates. Alternatively, de novo adhesion of the coadhering streptococcal strain to pellicles brushed on the wetted substratum yielded 31% of bacteria involved in large aggregates, but after brushing the immersed substratum only 12% of the adhering bacteria were found in large aggregates. It is concluded that non-contact sonic brushing, under immersion, removes high percentage of adhering bacterial pairs up to a distance of 6 mm between the brush and the pellicle surface. However, non-contact, sonic brushing with only a thin wet film on the substratum may leave footprints to which streptococci preferentially adhere.

Cell surface hydrophobicity is one of the most important factors controlling adhesion of microorganisms to surfaces. In this paper, cell surface properties of lactobacilli and recombinant lactobacilli with and without a surface layer protein (SLP) associated with cell surface hydrophobicity were determined, including water contact angles, zeta potentials as a function of pH, the nitrogen contents of the cell surface and adhesion to hexadecane. Two strains possessing an S-layer (Lactobacillus acidophilus ATCC4356 and L. crispatus JCM5810) showed the highest water contact angles (76 and 55degrees, respectively) and the highest N/C surface concentration ratios by X-ray photoelectron spectroscopy (0.172 and 0.160, respectively), indicative of the presence of S-layer proteins. L. casei 393*/CA5'A, with the SLP of L. crispatus JCM5810 anchored to its surface had higher water contact angles (62degrees) than its parent strain (32degrees). but no higher amount of cell surface nitrogen. However, anchoring of the SLP did stimulate its adhesion to hexadecane. LiCl treatment, removing Slayer and other non-covalently linked surface proteins, increased water contact angles and N/C ratios for L. crispatus JCM5810 and L. casei 393*/CA5'A, while L. acidophilus ATCC4356 showed a decrease in the N/C ratio like for L. gasseri LMG9203, that lacks an SLP. The isoelectric point of all but one Lactobacillus strain varied between 3.2 and 4.6, whereas strain L. crispatus JCM5810 was positively charged over the entire pH range. A hierarchical cluster analysis, using all cell surface hydrophobicity associated properties as input, yielded one cluster for strains possessing SLP, well separated from the other strains, including strains secreting SLP. It is concluded that SLP conveys hydrophobicity to the Lactobacillus cell surface and enhances its adhesion to hexadecane through hydrophobic interactions. (C) 2002 Elsevier Science B.V. All rights reserved.

In vitro salivary pellicles were found to be less hydrophobic by water contact angles than clinically formed pellicles. In this study, water contact angles were measured on enamel coated with pellicles adsorbed from reconstituted human whole saliva (RHWS) and after exposure to dentifrices or dietary components. In addition, adhesion of Streptococcus oralis J22 to pellicles formed from RHWS with minor amounts of milk added and after exposure to dentifrices was studied. Exposure of RHWS-pellicles to milk or salad oil yielded an increase in the hydrophobicity of in vitro pellicles to values observed in vivo, but a decrease was seen after exposure to a sugar solution. Pellicles formed from saliva with 0.4% milk added attracted less S. oralis cells than pellicles formed in the absence of milk components. Exposure of pellicles formed from saliva with milk added to various dentifrices had a variable effect on bacterial adhesion: markedly lower numbers of adhering S. oralis were found for a dentifrice with NaF, but exposure to dentifrices containing SnF2 or hexametaphosphate showed slightly increased adhesion. In summary, dietary components have influence on the hydrophobicity of enamel pellicles, while combinations of dietary components and dentifrices certainly influence the adhesiveness of the pellicles. The effects of dietary components on pellicle conditioning film should be taken into consideration in research on the development of ingredients to control intraoral surface chemistry and microbiology, as well as in the development of oral products.

One of the major drawbacks in the use of biomedical materials is the occurrence of biomaterials centered infections. After implantation, the host interacts with a biomaterial by forming a conditioning film on its surface and an immune reaction towards the foreign material. When microorganisms can reach the biomaterials surface they can adhere to it. Adhesion of microorganisms to an implant is mediated by their physico-chemical surface properties and the properties of the biomaterials surface itself. Subsequent surface growth of the microorganisms will lead to a mature biofilm and infection, which is difficult to eradicate by antibiotics. The purpose of this review is to give an overview of the mechanisms involved in biomaterials centered infection and the possible methods to prevent these infections. (C) 2002 Kluwer Academic Publishers.

Chemical and structural complexity of bacterial cell surfaces complicate accurate quantification of cell surfaces properties. The presence of fibrils, fimbriae or other surface appendages on bacterial cell surfaces largely influence those properties and would therefore play a major function in interfacial phenomena as aggregation and adhesion. The electrophoretic softness and fixed charge density in the polyelectrolyte layer of nine Streptococcus mitis strains, usually carrying long sparsely distributed fibrils, were determined by the soft particle analysis using measured electrophoretic mobilities as a function of the ionic strength. In general, S. mitis cell surfaces are electrophoretically soft (1.0-2.5 nm) with a fixed negative charge density of -1.2 to -4.3 x 10(6) Cm-3. Further, a comparison with surfaces of other bacterial strains that are reported to be soft indicates that the Ohshima soft layer model does not provide information on the surface morphology causing the softness. The most likely reason is that the electroosmotic flow occurs only in the very outer region of thick extracellular surface layers. Nevertheless, determining the surface softness is essential for proper characterization of the cell surface electrostatics.

The effect of two subinhibitory antibiotic concentrations of ampicillin and vancomycin during growth on the adhesion of Enterococcus faecalis 1131 to glass and silicone rubber was studied in a parallel plate flow chamber. Initial deposition rates and numbers of adhering bacteria after 4 h were higher on hydrophilic glass than on hydrophobic silicone rubber, regardless of growth conditions. The presence of 1/4 minimal inhibitory concentration (MIC) of ampicillin during growth reduced enterococcal adhesion to both substrata, but growth in the presence of 1/4 MIC vancomycin did not affect the adhesion of E faecalis. Moreover, enterococcal adhesion increased after growth in the presence of 1/8 MIC vancomycin. The increased adhesion after growth in the presence of subinhibitory concentrations of vancomycin may have strong implications for patients living with implanted biomaterials, as they may suffer adverse effects from use of this antibiotic, especially since bacteria once adhered are less sensitive to antibiotics. (C) 2001 Federation of European Microbiological Societies. Published by Elsevier Science BN. All rights reserved.

Many Staphylococcus epidermidis strains possess capsule or slime layers and consequently the staphylococcal cell surface should be regarded as a soft, polyelectrolyte layer allowing electrophoretic fluid flow through a layer of fixed charges. The presence of such a soft layer decreases the energy barrier due to electrostatic repulsion in the interaction of the organisms with negatively charged substrata [Morisaki, H., Nagai, S., Ohshima, H., Ikemoto, E. & Kogure, K. (1999), Microbiology 145, 2797-28021 and hence plays an important role in their adhesion. In this paper, the authors compare the electrophoretic softness and amount of fixed charge in the outer cell surface layers of 20 S. epidermidis strains, grown in a liquid medium or on a solid agar, as determined from the dependencies of their electrophoretic mobilities upon the ionic strength of a suspending fluid. Most of the staphylococcal cell surfaces were relatively soft, with a mean cell surface softness (1/lambda) for strains grown In liquid medium of 1.7+/-0.6 nm (standard deviation over all 20 strains) which is soft by comparison with a completely bald, peptidoglycan-rich streptococcal cell surface (1/lambda = 0.7 nm). When the staphylococcal strains were grown on solid agar, the cell surface softness of 17 of the 20 strains increased, sometimes by a factor of two. On average for 20 strains, the cell surface softness increased significantly (P

Biofilms on silicone rubber voice prostheses are the major cause for frequent failure and replacement of these devices. The presence of both bacterial strains and yeast has been suggested to be crucial for the development of voice prosthetic biofilms. Adhesive interactions between Candida albicans, Candida krusei, and Candida tropicalis with 14 bacterial strains, all isolated from explanted voice prostheses were investigated in a parallel plate flow chamber. Bacteria were first allowed to adhere to silicone rubber, after which the flow chamber was perfused with yeast, suspended either in saliva or buffer. Generally, when yeast were adhering from buffer and saliva, the presence of adhering bacteria suppressed adhesion of yeast. In saliva, Rothia dentocariosa and Staphylococcus aureus enhanced adhesion of yeast, especially of C. albicans. This study shows that bacterial adhesion mostly reduces subsequent adhesion of yeast, while only a few bacterial strains stimulate adhesion of yeast, provided salivary adhesion mediators are present. Interestingly, different clinical studies have identified R. dentocariosa and S. aureus in biofilms on explanted prostheses of patients needing most frequent replacement, while C. albicans is one of the yeast generally held responsible for silicone rubber deterioration.

Zeta potential distributions of five uropathogens were measured in urines collected after increased water intake, consumption of cranberry supplements, or intake of ascorbic acid by volunteers. Zeta potentials of bacteria in urine from ascorbic acid consumption shifted towards less negative values due to pH changes. Cranberry supplementation caused a shift in zeta potential distribution in a more positive direction possibly due to fructose and tannin metabolites, which are known to influence bacterial adhesion. The most negatively charged sub-populations of bacteria disappeared after increased water intake, believed to be caused by dilution of Tamm Horsfall Protein (THP). It is concluded that THP may adsorb to uropathogen cell surfaces to yield a more negative zeta potential, which thereby reduces uropathogen adhesion to surfaces through electrostatic repulsion. The ability to alter uropathogen cell surface properties by delivery of functional foods could have clinical significance in the pathogenesis and prevention of urinary tract infections. (C) 2000 Elsevier Science B.V. All rights reserved.

The release of biosurfactants by adhering microorganisms as a defense mechanism against other colonizing strains on the same substratum surface has been described previously for probiotic bacteria in the urogenital tract, the intestines, and the oropharynx but not for microorganisms in the oral cavity. Two Streptococcus mitis strains (BA and EMS) released maximal amounts of biosurfactants when they were grown in the presence of sucrose and were harvested in the early stationary phase. The S. mitis biosurfactants reduced the surface tensions of aqueous solutions to about 30 to 40 mi m(-2). Biochemical and physicochemical analyses revealed that the biosurfactants released were glycolipids. An acid-precipitated fraction was extremely surfactive and was identified as a rhamnolipidlike compound. In a parallel-plate flow chamber, the number of Streptococcus mutans NS cells adhering to glass with and without a salivary conditioning film in the presence of biosurfactant-releasing S. mitis BA and EMS (surface coverage, 1 to 4%) was significantly reduced compared with the number of S. mutans NS cells adhering to glass in the absence of S. mitis. S. mutans NS adhesion in the presence of non biosurfactant-releasing S. mitis BA and EMS was not reduced at all. In addition, preadsorption of isolated S. mitis biosurfactants to glass drastically reduced the adhesion of S. mutans NS cells and the strength of their bonds to glass, as shown by the increased percentage of S. mutans NS cells detached by the passage of air bubbles through the flow chamber. Preadsorption of the acid-precipitated fraction inhibited S. mutans adhesion up to 80% in a dose-responsive manner. These observations indicate that S. mitis plays a protective role in the oral cavity and protects against colonization of saliva-coated surfaces by cariogenic S. mutans.

Objectives: To investigate whether synthetic salivary antimicrobial peptides have an inhibitory effect on the growth of bacteria and yeasts isolated from used silicone rubber voice prostheses. Methods: The antimicrobial activities of six synthetic salivary peptides (histatin 5, dhvar1, dhvar4, dhvar5, lactoferrin b 17-30 [LFb 17-30], and cystatin 51-15) at concentrations of 2 and 4 mg/mL were determined against different oropharyngeal yeast (four) and bacterial (eight) strains and against a "total microflora" isolated from explanted voice prostheses using agar diffusion tests. The spectrum of susceptible microorganisms was determined qualitatively. Results: Histatin 5 and cystatin 51-15 did not show any antimicrobial activity against the microorganisms involved in this study. Dhvar1 was active against some of the oropharyngeal microorganisms tested, including the yeast strains, but not against Rothia dentocariosa, Staphylococcus aureus, Escherichia coli and the total microflora. Dhvar4 was active against all microorganisms tested, including the total microflora, Dhvar5 lacked activity against E coli and the total microflora. LFb 17-30 did not inhibit the growth of any of the yeast strains involved and showed only minor activity against some of the bacterial strains. LFb 17-30 slightly inhibited the growth of the total microflora from an explanted prosthesis. Conclusions: The synthetic salivary peptide dhvar1 has a broad antimicrobial activity against all microorganism that are commonly isolated from explanted voice prostheses, including yeasts. Therewith, it may represent a useful drug, as an alternative for antibiotics and antimycotics employed in various ways to prolong the Lifetime of voice prostheses in laryngectomees.

Acid-base interactions play an important role in adhesion, including microbial adhesion to surfaces. Qualitatively acid-base interactions in microbial adhesion can be demonstrated by comparing adhesion to hexadecane (a negatively charged interface in aqueous solutions, unable to exert acid-base interactions) and chloroform (able to exert acid-base interactions) from aqueous suspensions of microorganisms. For 31 different microbial strains (4 Escherichia coli, 4 Enterococcus faecalis, 4 lactobacilli, 10 staphylococci, 9 streptococci) in low and high ionic strength potassium phosphate buffers, adhesion to chloroform was initially faster and in a stationary end-point more extensive than to hexadecane, due to acid-base interactions additionally operative from chloroform. However, a quantitative surface thermodynamical analysis of acid-base interactions based on water, formamide, methylene iodide and a-bromonaphthalene contact angles failed to explain the adhesion data obtained at low ionic strength, likely because of interference of electrostatic interactions. A weak relationship between initial removal rates and the acid-base interfacial free energy of adhesion was observed for the high ionic strength data, provided the analysis was confined to strains with an absolute zeta potential less than 15 mV. Similarly, a weak relationship was obtained between the Gibbs free energy of partitioning, calculated from the stationary end-point adhesion of the strains, and the acid-base interfacial free energy of adhesion. It is concluded that acid-base interactions play a definitive role in microbial adhesion, but the extent to which thermodynamically determined acid-base interactions eventually become operative in microbial adhesion may vary from strain to strain due to the presence of structural appendages and chemical heterogeneities on microbial cell surfaces.

Candida albicans surfaces are extremely sensitive to changes in growth conditions. In this study, adhesion to glass of aerated and non-aerated C. albicans ATCC 10261 in the presence and absence of adhering Streptococcus gordonii NCTC 7869 was determined in a parallel plate flow chamber. In addition, the influence of aeration on the yeast cell surface hydrophobicity, surface charge, and elemental cell surface composition was measured. S. gordonii adhering at the glass surface caused a reduction in the initial deposition rate of C. albicans, regardless of aeration. In a stationary end-point, only adhesion of nonaerated C. albicans was suppressed by the adhering S. gordonii. Non-aerated yeasts had a higher O/C elemental surface concentration ratio, indicative of cell surface polysaccharides, than aerated yeasts, at the expense of nitrogen-rich cell surface proteins. Both yeasts were essentially uncharged, but the nitrogen-rich cell surface of aerated yeasts had a slightly higher water contact angle than non-aerated yeasts. Summarizing, this study suggests that highly localized, hydrophobic cell surface proteins on C. albicans are a prerequisite for their interaction with adhering streptococci. (C) 1999 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.

The detachment of polystyrene particles adhering to collector surfaces with different electrostatic charge and hydrophobicity by attachment to a passing air bubble has been studied in a parallel plate flow chamber. Particle detachment decreased linearly with increasing air bubble velocity and decreasing liquid/vapour interfacial tension, regardless of the collector surface properties. However, particle detachment from hydrophilic, positively charged surfaces [3-(2-aminoethylamino)propyldimethoxysilane-coated glass, water contact angle 33 degrees] was most sensitive to variations in air bubble velocity and liquid/vapour interfacial tension, while detachment from hydrophobic, negatively charged surfaces (dimethyldichlorosilane-coated glass, water contact angle 96 degrees) was affected least. The influence of air bubble velocity was predominantly through the bubble/particle contact time, which needs to be long enough to allow sufficient thinning of the liquid film between the bubble and the particle for the detachment forces to become effective. On the hydrophobic collector surfaces, this thinning is assisted by a nearly spontaneous de-wetting of the collector surface, therewith decreasing the influence of other factors, such as air bubble velocity or liquid/vapour interfacial tension. Upon multiple passages of air bubbles approximately 80% of the particles were eventually detached, regardless of the properties of the collector surfaces, illustrating that the probabilities of detachment by multiple air bubble passages are additive.

Micron-sized particles adhering to collector surfaces can be detached by passing a liquid-air interface over the adhering particles. Theoretically, the efficiency of particle detachment depends on the interface velocity, the liquid surface tension, the viscosity, and the particle-substratum interaction forces. In this study we perfuse an air bubble through a parallel-plate flow chamber to study detachment of polystyrene particles from a quartz collector surface, at different interface velocities and liquid surface tensions and upon multiple air bubble passages. A linear relation was found between particle removal and the liquid-air interface velocity, with negligible removal at elevated velocities. Linear relations were also found between particle removal and the liquid-air surface tensions, with different slopes for different air bubble velocities. Particle removal could be increased by the passage of multiple air bubbles. In summary, this study shows that liquid-air interfaces can be employed to detach micron-sized particles from collector surfaces. The detachment process can be optimized by adjusting the air bubble velocities, the surface tensions, and the number of bubbles applied.

Adhesive interactions between Candida albicans and oral bacteria are generally thought to play a crucial role in the microbial colonization of denture acrylic, which may lead to denture stomatitis. This study investigated the influence of saliva on the adhesive interactions between C. albicans and Streptococcus sanguis or Actinomyces naeslundii on denture acrylic. First, bacteria were allowed to adhere to the acrylic surface from a flowing suspension, and subsequently yeasts were flowed over the acrylic surface. The organisms were assayed in the presence or absence of human whole saliva. All experiments were carried out in a parallel plate flow chamber and enumeration was done in situ with an image analysis system. In the absence of adhering bacteria, adhesion of C. albicans from buffer was more extensive than from saliva. However, in the presence of adhering bacteria, yeast adhesion from saliva was increased with respect to adhesion of yeasts from buffer, indicating that specific salivary components constitute a bridge between bacteria and yeasts. In all cases, yeast aggregates consisting of 3 to 5 yeast cells were observed adhering to the surface. A surface physico-chemical analysis of the microbial cell surfaces prior to and after bathing the microorganisms in saliva, suggests that this bridging is mediated by acid-base interactions since all strains show a major increase in electron-donating surface free energy parameters upon bathing in saliva, with no change in their zeta potentials. The surface physico-chemical analysis furthermore suggests that S. sanguis and A. naeslundii may use a different mechanism for adhesive interactions with C. albicans in saliva.

Adhesive interactions between yeasts and bacteria are important in the maintenance of infectious mixed biofilms on natural and biomaterial surfaces in the human body. In this study, the extended DLVO (Derjaguin-Landau-Verwey-Overbeek) approach has been applied to explain adhesive interactions between C. albicans ATCC 10261 and S. gordonii NCTC 7869 adhering on glass. Contact angles with different liquids and the zeta potentials of both the yeasts and bacteria were determined and their adhesive interactions were measured in a parallel-plate flow chamber. Streptococci were first allowed to adhere to the bottom glass plate of the flow chamber to different seeding densities, and subsequently deposition of yeasts was monitored with an image analysis system, yielding the degree of initial surface aggregation of the adhering yeasts and their spatial arrangement in a stationary end point. Irrespective of growth temperature, the yeast cells appeared uncharged in TNMC buffer, but yeasts grown at 37 degrees C were intrinsically more hydrophilic and had an increased electron-donating character than cells grown at 30 degrees C. All yeasts showed surface aggregation due to attractive Lifshitz-van der Waals forces. In addition, acid-base interactions between yeasts, yeasts and the glass substratum, and yeasts and the streptococci were attractive for yeasts grown at 30 degrees C, but yeasts grown at 37 degrees C only had favorable acid-base interactions with the bacteria, explaining the positive relationship between the surface coverage of the glass by streptococci and the surface aggregation of the yeasts. (C) 1999 Academic Press.

Depositions of negatively charged polystyrene particles in a parallel plate flow chamber to negatively and positively charged collector surfaces are compared at different shear rates and ionic strengths. The observation of adhering particles was done in situ during the deposition process with the aid of an image analyzer and the adsorption and desorption of each particle was monitored individually using a special tracking algorithm. Initial deposition rates j(0)(EXP) were higher to positively charged glass than to negatively charged glass collector surfaces, depending on shear rates and ionic strength. All observed experimental deposition rates were, however, smaller than the Smoluchowski-Levich (SL) approximate solution of the convective-diffusion (CD)equation. Initial deposition rates were also calculated using an exact numerical solution of the CD equation; they were two times higher than the experimentally observed deposition rates for positively charged glass and about equal or lower for negatively charged glass. The desorption rates j(des)(t) Of polystyrene particles on positively charged glass were nearly zero under all conditions, whereas the desorption rates from the negatively charged glass were considerable and finally balanced the adsorption rates j(ads)(t). From the residence time dependent desorption probability beta(t - tau), it could be determined that polystyrene particles on negatively charged collector surfaces have the highest probability of desorption within the first 5-10 min after deposition. Experimental results were subsequently compared with those from a proposed adsorption-desorption model for deposition kinetics, using the parameters derived as an input, and with a Monte Carlo simulation of the deposition process. A high degree of similarity between experimental results, the adsorption-desorption model and the Monte Carlo simulation results was observed, which indicates; the consistency of the applied experimental methods and theoretical models.

PMMA (poly-methyl-methacrylate) bone cement is widely used in prosthetic implant surgery and is currently prepared with vacuum-mixing for improved mechanical properties. Revision of implants due to infection occurs in about 1% of cases, mostly involving staphylococcal strains. Antibiotic loaded cementis often used in this revision-setting. The aims of this study were to determine in a modified Robbins device whether gentamicin loaded PMMA bone cements (2.5 weight percent, CMW; 1.25 weight percent, Palaces) inhibit Staphylococcus aureus ATCC 12600 biofilm formation, and whether vacuum-mixing or hand-mixing of the antibiotic loaded cements have an effect on biofilm inhibition. The results show that CMW antibiotic loaded bone cement reduced biofilm formation by 42 and 63% compared with the unloaded cement for vacuum- and hand-mixed, respectively. Palaces, however, despite possessing half the concentration of gentamicin, demonstrated a biofilm reduction of 16 and 43% compared with the unloaded cement for vacuum- and hand-mixed, respectively. High vacuum mixing of the CMW antibiotic loaded bone cement resulted in an apparent increase in biofilm formation. It is concluded that the antibiotic content of gentamicin loaded bone cements can be reduced to lower doses than effective for reducing biofilm formation by increasing the vacuum applied during preparation. In addition, increased antibiotic concentrations in a cement are not necessarily accompanied by a greater reduction in biofilm formation.

The infection risk of biomaterial implants is determined by an interplay of bacterial adhesion and surface growth of the adhering organisms. In this study, we compared initial adhesion and surface growth of Pseudomonas aeruginosa AK1 (zeta potential -7 mV) on negatively charged (PMMA/MAA, zeta potential -18 mV) and positively charged (PMMA/TMAEMA-Cl, zeta potential +12 mV) methacrylate copolymers in situ in a parallel plate flow chamber. Initial adhesion was measured using phosphate-buffered saline and subsequent surface growth of the adhering bacteria using nutrient broth as growth medium. Initial adhesion was twice as fast on the positively charged methacrylate than on the negatively charged copolymer. Surface growth, however, was absent on the positively charged copolymer, while on the negatively charged methacrylate the number of bacteria increased exponentially during surface growth with a generation time of 32 min. From the results of this study it can be concluded that positively charged biomaterial surfaces might show reduced risks of biomaterials-centered infections, despite being more adhesive. (C) 1999 Kluwer Academic Publishers.

After total laryngectomy, the voice can be restored successfully with a silicone tracheo-oesophageal voice prosthesis. Biofilm formation and subsequent deterioration of the silicone material of the prosthesis often limit the mean life of the device to an average of 3-5 months. Although device replacement can be considered an easy outpatient procedure. frequent replacements are inconvenient for the patient and may lead to malfunction of the tracheo-oesophageal fistula. Further understanding of the process of development and inhibition of the colonization of these polymer surfaces requires several comprehensive clinical studies. How ever, iii vivo research of the biomaterials of the voice prostheses is difficult and time consuming. In order to simulate the natural process of biofilm development under dynamic nutrient conditions, an artificial throat was developed. Biofilm developed on Groningen(R) button voice prostheses iii vitro a could not be distinguished from that formed over several months in,vitro. This method can be used as a standardized approach for studying functional and structural aspects of all commercially available indwelling and non-indwelling voice prostheses, including the Groningen(R) button, Provox(R), Voice Master(R), Blom-Singer(R) and others under various laboratory conditions.

Purpose. To compare the efficacies of two all-in-one contact lens (CL) cleaning solutions and a detergent mixture on the detachment of a pathogenic bacterium adhering to two types of contact lenses in the absence and presence of a tear film. Methods. Bacterial-detachment studies were carried out in a parallel-plate flow chamber. Rigid gas permeable (RGP) CLs with and without a tear film were fixed on the bottom plate of the flow chamber. After adhesion of Pseudomonas aeruginosa no. 3, bacterial detachment was stimulated by perfusing the system either with an all-in-one CL-cleaning solution, for soft contact lenses (SCL solution) and for rigid lenses (RCL solution), or with a detergent mixture of 0.25% (wt/vol) sodium lauryl sulfate (SLS) and 0.2% sodium methyl cocoyl taurate (Tauranol). In addition, the all-in-one RCL-cleaning solution supplemented with 0.025% (wt/vol) SLS and 0.02% (wt/vol) Tauranol was evaluated. A surface physical-chemical analysis of the lenses before and after application of the solutions was done to determine whether remnants of the ophthalmic solutions or detergents could be found adsorbed to the CL surfaces. Results. Both all-in-one CL-cleaning solutions stimulated minor bacterial detachment from CL surfaces with or without a tear film. The SLS/Tauranol detergent mixture, however, removed less than or equal to 95% of the adhering P. aeruginosa cells, whereas the RCL-cleaning solution supplemented with detergents also stimulated significant detachment. Surface physical-chemical analysis clearly demonstrated the presence of a tear film on the CL surfaces, but remnants neither of the ophthalmic solutions nor of the detergents could be found. Conclusion. Ophthalmic solutions are not effective in stimulating detachment of adhering bacteria from CL surfaces. Supplementing of an all-in-one CL-cleaning solution with only small amounts of detergents yielded a solution much more effective in stimulating bacterial detachment while leaving no detectable remnants of the ophthalmic solution or of the detergents on the CL surfaces.

The adhesion of Actinobacillus actinomycetemcomitans is a virulence factor in the aetiology of periodontitis and is determined by physico-chemical properties, e.g. surface charge and hydrophobicity, of the bacterial cell surface. Although oral surfaces are constantly coated with saliva, few studies have dealt with the binding of A. actinomycetemcomitans with saliva. In this report, the charge properties of A. actinomycetemcomitans have been studied through measurement of the zeta potential and the saliva-bacteria interaction investigated at different pH-values. At physiological conditions the zeta potential was negative, varying from -11 to -26 mV, for two laboratory and two fresh isolates of A. actinomycetemcomitans. Under these conditions, binding of the low-molecular-weight salivary mucin, lactoferrin, and S-IgA was confirmed using salivary samples and purified salivary fractions in liquid-phase and in ELISA. The iso-electric points of the laboratory and fresh clinical isolates of A. actinomycetemcomitans were determined at pH 4.6 and 3.8, respectively. At pH below the iso-electric point, giving positive values of the zeta potential, additional salivary protein species bound to A. actinomycetemcomitans, including the high-molecular-weight salivary mucin (MG1) and agglutinin. Binding of the low-molecular-weight salivary mucin (MG2), lactoferrin, and S-IgA, was hardly affected by this change in zeta potential. A salivary coating formed on the bacterium at pH 7 reduced the zeta potential of the laboratory strain Y4 greatly and an iso-electric point for the bacterium could not be determined. Overall, the study suggests that upon changes in environmental pH additional salivary attachment sites on the micro-organism are exposed.

Patients who undergo a total laryngectomy usually receive a silicone rubber voice prosthesis for voice rehabilitation. Unfortunately, biofilm formation on the esophageal side of voice prostheses limits their lifetime to 3-4 mon on average. The effects of repeated argon plasma treatment of medical grade, hydrophobic silicone rubber on in vitro adhesion and growth of bacteria and yeasts isolated from voice prostheses, as well as in vivo biofilm formation are presented here. In vitro experiments demonstrated that initial microbial adhesion over a 4 h time span to plasma-treated, hydrophilized, silicone rubber was generally less than on original, hydrophobic silicone rubber, both in the absence and presence of a salivary conditioning film on the biomaterial. Growth studies over a time period of 14 d at 37 degrees C in a modified Robbins device, showed that fewer Candida cells adhered on plasma-treated, hydrophilized silicone rubber as compared to on original, hydrophobic silicone rubber. For the in vivo evaluation of biofilm formation on plasma-treated silicone rubber voice prostheses, seven laryngectomized patients received a partly hydrophilized "Groningen Button" voice prosthesis for a planned evaluation period of 4 wk. After removal of the voice prostheses, the border between the hydrophilized and the original, hydrophobic side of the prostheses was clearly visible. However, biofilm formation was, unexpectedly, less on the original, hydrophobic sides, although the microbial compositions of the biofilms on both sides were not significantly different. Summarizing, this study demonstrates that in vitro microbial adhesion and growth on silicone rubber can be reduced by plasma treatment, but in vivo biofilm formation on silicone rubber voice prostheses is oppositely enhanced by hydrophilizing the silicone rubber surface. Nevertheless, from the results of this study the important conclusion can be drawn that in vivo biofilm formation on voice prostheses is controlled by the hydrophobicity of the biomaterials surface used. (C) 1998 Chapman & Hall.

In this study, the position bound shape, spreading, detachment and migration of adhering HUVEC endothelial cells on dichlorodimethylsilane (DDS) chemical gradient surfaces was investigated during exposure to flow in a parallel plate flow chamber in the presence of` serum proteins. Gradient surfaces were prepared by the diffusion method and characterized by the Wilhelmy plate technique for their wettability. Ln order to measure the possible influence of wettability steepness on the position bound cellular response. shallow and steep wettability gradients were prepared by applying two different diffusion times and DDS-concentrations. Quantitative analyses of the cellular response on the gradient surfaces showed that the position bound spread area and,shape Factor of adhering cells increased when going from the hydrophobic to the hydrophilic end, concurrent with the steepness of the gradient. After exposure to Row, cells detached immediately from the hydrophobic side and maintained their positions more easily on the hydrophilic side. Furthermore, it was shown that the pc:,position bound detachment and migration of cells depended on the steepness of` the wettability gradient and the direction of the flow. When the Row was to the hydrophilic end, migration velocity did not vary along the length of the gradients, and was lower on the steep (approximately 2 mu m/min) than on the shallow (approximately ly 3 mu m/min) gradients. However, when flow was to the hydropbobic end, migration velocities appeared position bound and were higher on the hydrophobic ends of both gradients.

Background. The consequences of a life-saving laryngectomy are still very distressing. The Eureka project "Artificial Larynx" aims at realization of an implantable artificial larynx to eliminate all drawbacks. Methods. The artificial larynx will consist of artificial vocal folds of adjustable pitch and variable frequency during speech, an artificial epiglottis controlled by muscles, a valve mechanism to switch between breathing and speaking, and a tissue connector to connect the artificial larynx to the trachea. Results. The valve mechanism has been designed and built and it can already be used as a tracheostoma valve. For the voice-producing element we intend to use mechanical and electrical vibrating principles. Potential principles are selected and will be built as prototype. A tissue connector with a porous surface has been designed. Research will focus on optimal materials for soft tissue ingrowth. To prevent bacterial and fungal adhesion to the artificial larynx the adhesion process to silicone rubber shunt valves has been analyzed. Bacterial colonization is followed by more harmful yeast strains. The materials resistance to this adhesion process will be developed. Conclusions. Numerous problems have to be solved. Each solution. however, can be applied already to improve the existing rehabilitation process of laryngectomized patients.