Biomedical subjects

H C Van der Mei

Publications and source records attributed to H C Van der Mei.

14 recordsLinked to original sources

PubMed2003

Influence of the Provox Flush, blowing and imitated coughing on voice prosthetic biofilms in vitro.

OBJECTIVE: This study investigates the effect of regular airflow, as an isolated single factor, through Groningen and Provox2 voice prostheses on biofilm formation. MATERIAL AND METHODS: Groningen and Provox2 voice prostheses were placed in a modified Robbins device and inoculated with the total microflora from an explanted Groningen voice prosthesis. After 3 days, prostheses were either flushed 3 times per day with the Provox flush, treated with an airflow using an increasing order of air pressure (10, 15 and 20 cmH2O) or vigorously perfused by means of imitated coughing (air pressure 20 cmH2O). As a control, prostheses were left undisturbed to promote biofilm growth. Following flushing, blowing or coughing, each artificial throat was perfused with 200 ml of phosphate-buffered saline. This procedure was repeated three times a day for 9 days. At the end of each day, the artificial throats were filled with growth medium for 30 min and left empty during the night after draining. After 12 days the microflora on each voice prosthesis was quantified by plating on blood agar for bacteria and on de Man, Rogosa and Sharpe agar for yeasts. RESULTS: The use of the Provox flush reduced bacterial prevalence on Groningen and Provox2 voice prostheses to 71% and 45% of the control values, respectively, without affecting the number of yeasts. Increasing airflows and imitated coughing yielded reductions of 45-70% in bacterial and yeast prevalence on Provox2 voice prostheses. On the Groningen voice prostheses the effects of increasing airflows and imitated coughing were less pronounced: reductions in bacterial and yeast prevalence of 56-87% were observed. CONCLUSION: This study shows that use of the Provox flush has a cleansing effect, especially on Provox2 voice prostheses, and furthermore suggests that daily airflow through voice prostheses as part of a daily maintenance scheme reduces biofilm formation and can be expected to prolong the life of these devices.

Air↗

PubMed2000

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.

Animals↗

PubMed1999

Plasticizers increase adhesion of the deteriogenic fungus Aureobasidium pullulans to polyvinyl chloride.

Initial adhesion of fungi to plasticized polyvinyl chloride (pPVC) may determine subsequent colonization and biodeterioration processes. The deteriogenic fungus Aureobasidium pullulans was used to investigate the physicochemical nature of adhesion to both unplasticized PVC (uPVC) and pPVC containing the plasticizers dioctyl phthalate (DOP) and dioctyl adipate (DOA). A quantitative adhesion assay using image analysis identified fundamental differences in the mechanism of adhesion of A. pullulans blastospores to these substrata. Adhesion to pPVC was greater than that to uPVC by a maximum of 280% after a 4-h incubation with 10(8) blastospores ml(-1). That plasticizers enhance adhesion to PVC was confirmed by incorporating a dispersion of both DOA and DOP into the blastospore suspension. Adhesion to uPVC was increased by up to 308% in the presence of the dispersed plasticizers. Hydrophobic interactions were found to dominate adhesion to uPVC because (i) a strong positive correlation was observed between substratum hydrophobicity (measured by using a dynamic contact angle analyzer) and adhesion to a range of unplasticized polymers including uPVC, and (ii) neither the pH nor the electrolyte concentration of the suspension buffer, both of which influence electrostatic interactions, affected adhesion to uPVC. In contrast, adhesion to pPVC is principally controlled by electrostatic interactions. Enhanced adhesion to pPVC occurred despite a relative reduction of 13 degrees in the water contact angle of pPVC compared to that of uPVC. Furthermore, adhesion to pPVC was strongly dependent on both the pH and electrolyte concentration of the suspension medium, reaching maximum levels at pH 8 and with an electrolyte concentration of 10 mM NaCl. Plasticization with DOP and DOA therefore increases adhesion of A. pullulans blastospores to pPVC through an interaction mediated by electrostatic forces.

Ascomycota↗

PubMed1999

The effect of water, ascorbic acid, and cranberry derived supplementation on human urine and uropathogen adhesion to silicone rubber.

In this study, urine was collected from groups of volunteers following the consumption of water, ascorbic acid, or cranberry supplements. Only ascorbic acid intake consistently produced acidic urine. Photospectroscopy data indicated that increased water consumption produced urine with lower protein content. Surface tension measurements of the collected urine showed that both water and cranberry supplementation consistently produced urine with surface tensions higher than the control or urine collected following ascorbic acid intake. These urine samples were also employed to study uropathogen adhesion to silicone rubber in a parallel plate flow chamber. Urine obtained after ascorbic acid or cranberry supplementation reduced the initial deposition rates and numbers of adherent Escherichia coli and Enterococcus faecalis, but not Pseudomonas aeruginosa, Staphylococcus epidermidis, or Candida albicans. Conversely, urine obtained from subjects with increased water intake vastly increased the initial deposition rates and numbers of adherent E. coli and E. faecalis (P < 0.05).

Adult↗

PubMed1999

Time-related contact angle measurements with human plasma on biomaterial surfaces.

Axisymmetric drop shape analysis by profile (ADSA-P) was used to assess in time contact angle changes of human plasma drops placed on four different biomaterials. Results were related with conventional blood compatibility measurements: albumin adsorption, fibrinogen adsorption and platelet adhesion. While contact angle measurements with water are material-related but constant in time, contact angle measurements with plasma changed over time owing to protein adsorption on the solid-liquid interface. The contact medium plasma did not influence the initial contact angle. Contact angles on PDMS decreased most in time (41 degrees) and demonstrated highest levels of conventionally measured albumin and fibrinogen adsorption and platelet adhesion. PTFE, with the lowest contact angle decrease over a 500 minutes period (19 degrees), showed low fibrinogen and albumin adsorption as well as low platelet adhesion. PU and HDPE demonstrated almost similar initial contact angles with plasma and contact angle decreases (26 and 27 degrees), intermediate protein adsorption, and platelet adhesion. We conclude that biocompatibility properties of the tested materials may be more related to the behaviour of their contact angles in time, than to the initial hydrophobic or hydrophilic state.

Adsorption↗

PubMed1998

The interaction between saliva and Actinobacillus actinomycetemcomitans influenced by the zeta potential.

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.

Actinobacillus↗

PubMed1995

Effects of ciprofloxacin and vancomycin on physicochemical surface properties of Staphylococcus epidermidis, Escherichia coli, Lactobacillus casei and Lactobacillus acidophilus.

Under clinical conditions, during antibiotic treatment, micro-organisms often grow at sub-inhibitory concentrations. This may lead to altered adhesive cell surface properties and to a disruption of the indigenous microflora, in addition to the creation of a more pathogenic biofilm. The effects of growing Staphylococcus epidermidis, Escherichia coli and lactobacilli in the presence of sub-inhibitory concentrations of ciprofloxacin and vancomycin were determined. Growing the cells under antibiotic burden sometimes led to altered cell surface hydrophobicity (by adhesion to hexadecane), changes in the pH-dependence of zeta potentials, and elemental surface compositions or in different SDS-PAGE protein profiles. For several isolates only one of the surface properties was altered by the presence of an antibiotic in the growth medium and no systematic effects were observed for all isolates representing a certain species or even strain. The important conclusion to be drawn from the results of this study is that the effects of growing cells under antibiotic burden on their adhesive cell surface properties can only be established when using a variety of techniques.

Alkanes↗

PubMed1994

Microflora on explanted silicone rubber voice prostheses: taxonomy, hydrophobicity and electrophoretic mobility.

Silicone rubber voice prostheses are implants which are inserted in a non-sterile environment and therefore become quickly colonized by micro-organisms. The micro-organisms exist on the medical grade silicone rubber as mixed biofilms of bacteria and yeasts. A total of 79 bacterial and 39 yeast strains were isolated from these biofilms by soft ultrasonic treatment. Gram-positive/catalase-negative and Gram-positive/catalase-positive cocci represented the dominant bacterial strains. The yeasts were mainly Candida species. Further characterization of cell surface properties such as hydrophobicity by microbial adhesion to hexadecane and electrophoretic mobility showed a distinct difference when the bacterial strains were compared with the yeasts. The bacterial hydrophobicities ranged from 0 to 100% adhesion to hexadecane, whereas the yeast strains, especially the Candida albicans strains, all had markedly hydrophilic cell surfaces. A comparison of the electrophoretic mobilities showed also differences between bacteria and yeast. The values for the bacteria were found to be between -2.5 to -0.5 (10(-8) m2 V-1 s-1), whereas for the yeasts electrophoretic mobilities were more positive. Based on the adhesive properties of the isolated micro-organisms, strategies can now be developed to modify the properties of the silicone rubber to reduce biofilm formation on such prostheses.

Candida↗

PubMed1994

The influence of surface-free energy on supra- and subgingival plaque microbiology. An in vivo study on implants.

The influence of surface free energy on supra- and subgingival plaque microbiology was examined in 9 patients with functional fixed prostheses supported by endosseous titanium implants. Two abutments (trans-mucosal part of the 2 stage implant) were replaced by either a new titanium abutment or a fluor-ethylene-propylene (FEP) coated abutment per subject. After 3 months of habitual oral hygiene, plaque samples were taken. Supragingival plaque was examined by means of differential phase-contrast microscopy, whereas for the subgingivial plaque additional analyses (DNA probes analysis, culturing) were performed. The subgingival samples were taken by paper-points and by scraping of the subgingival abutment surface. Differential phase-contrast microscopy showed a significant difference in plaque composition, especially when supragingival plaque was considered (P = 0.05). FEP coated abutments frequently harbored more coccoid microorganisms, whereas spirochetes or motile organisms were only detected around titanium abutments. Subgingivally, the number of colony forming units (CFU) in paper-points was comparable for both types of abutments. If the to-the-abutment-adhering plaque was considered, the number of CFU was 5 times higher on the titanium abutments than on the FEP coated abutments. However, this difference did not reach a statistical level of significance (P = 0.38). The DNA probe analysis of the subgingival plaque collected with paper-points showed a slightly higher frequency and concentration of perio-pathogens around the titanium abutments. However, the inter-substratum differences were smaller than the inter-subject differences. The latter seemed to be related to patient's dental status.(ABSTRACT TRUNCATED AT 250 WORDS)

Bacterial Adhesion↗

PubMed1993

Biodeterioration of medical-grade silicone rubber used for voice prostheses: a SEM study.

Silicone voice prostheses used for rehabilitation of speech after total laryngectomy are inserted in an non-sterile habitat. Deposits on explanted Groningen Button voice prostheses revealed a biofilm, due to heavy colonization of the silicone surface by bacteria and yeasts. Furthermore, it was demonstrated by scanning electron microscopy on sectioned explants that the silicone material was deteriorated by filamentous and vegetative yeast cells. The different explants showed a variety of sharp-edged, discrete yeast colonies. The yeasts grew just under the silicone surface and up to 700 microns into the silicone material. Finally, nine different types of defects in the silicone material created by the yeasts are described. This deterioration of the silicone by yeasts seems to be the main reason for the failure and the frequent replacement of the prostheses. The mechanisms of silicone deterioration are still hypothetical.

Bacterial Adhesion↗

PubMed1993

A critical appraisal of positive cooperativity in oral streptococcal adhesion: Scatchard analyses of adhesion data versus analyses of the spatial arrangement of adhering bacteria.

Positive cooperativity is a mechanism proposed to account for the adhesion of bacteria to surfaces. In this paper, two methods that both claim to assess experimentally cooperative phenomena, viz. Scatchard analysis of adhesion data (using adhesion to vials) and analysis of the spatial arrangement of adhering cells (using a flow chamber), were compared and critically evaluated. Three oral strains were used and the substrata involved were glass (hydrophilic) and silicone-coated glass (hydrophobic) employed with or without a salivary coating. Scatchard analysis and near-neighbour analysis of adhering cells yield similar conclusions with regard to the mechanism of adhesion of the cells, provided that adhering cells are sufficiently immobilized under the experimental conditions. In the case of incomplete immobilization, near-neighbour collection results from sliding of adhering cells rather than from cooperative phenomena. Also, the agreement between the conclusions from both methods seems to be better, the more reversibly the cells adhere. Positive cooperativity can be absent or present on saliva-coated substrata with a distinct effect of the substratum hydrophobicity, despite the presence of an adsorbed film. This suggests that a different pellicle develops on a hydrophobic substratum than on a hydrophilic substratum. This is confirmed by our observation that the amino acid composition of salivary films is different on both types of substratum.

Bacterial Adhesion↗

PubMed1992

Development and use of a parallel-plate flow chamber for studying cellular adhesion to solid surfaces.

A parallel-plate flow chamber is developed in order to study cellular adhesion phenomena. An image analysis system is used to observe individual cells exposed to flow in situ and to determine area, perimeter, and shape of these cells as a function of time and shear stress. With this flow system the behavior of human fibroblasts spread on glass is studied when exposed to an increasing laminar flow. The flow system appears to be well-suited for following individual cells during detachment. After 75 to 90 min, at a shear stress of 350 dynes/cm2, more than 50% of the spread cells are detached from the surface. Cells with higher spreading areas stay longer at the glass surface. Cells round up before detaching. Sometimes the cell body is attached to the substratum through a thin filament during detachment. At the scanning electron microscopy level numerous filopodial extensions are observed. Cell material could only rarely be observed at the light or scanning electron microscopic level on the substratum once a cell was detached.

Biophysical Phenomena↗

PubMed1992

Adhesion of mutants streptococci to glass with and without a salivary coating as studied in a parallel-plate flow chamber.

Deposition and adhesion to glass with and without a salivary coating in a parallel-plate flow chamber were studied with four strains of mutans streptococci. Stationary-state adhesion of the strains to uncoated glass ranged from 0.3 x 10(6) cm-2 (Streptococcus rattus HG218) to 12.7 x 10(6) cm-2 (Streptococcus sobrinus HG1025) and generally decreased after saliva coating of the glass. The poor adhesion found for S. rattus HG218 to both uncoated and saliva-coated glass could be due to its relatively high negative surface-charge. Deposition efficiencies of all strains were greater than or equal to 1 for uncoated glass and decreased greatly after saliva coating of the glass. Possibly, adhesion to a saliva coating is less efficient and more time-consuming than that to uncoated glass, because stereochemical groups in the pellicle and on the cell surfaces may have to re-arrange before an effective interaction can occur. Desorption rates, measured 1000 s and 5000 s after the start of an experiment, decreased by a factor of ten upon a five-fold increase in contact time, indicative of a two-phase adhesion process. Of the four strains studied, only Streptococcus cricetus HG737 showed a minor positive cooperativity on saliva-coated glass, possibly mediated by surface appendages observed by transmission electron microscopy on negatively-stained cells. Retention of adhering bacteria was strain-dependent on uncoated glass, but was identical for all strains on saliva-coated glass, which suggests that the structure and composition of the pellicle may be more important with respect to the retention of adhering cells than the cell-surface properties themselves.

Bacterial Adhesion↗

PubMed1992

Heterogeneity of surfaces of subgingival bacteria as detected by zeta potential measurements.

Porphyromonas gingivalis, Prevotella intermedia, and Actinobacillus actinomycetemcomitans (A.a.) are Gram-negative bacteria which are implicated in various forms of periodontal disease. The Gram-positive Peptostreptococcus micros may also play an important role. For investigation of the possible adhesion and colonization mechanisms of these organisms, the charge properties of the outermost layers of bacterial cell surfaces were studied through the measurement of zeta potentials at various pH values. Eleven fresh clinical isolates, representing the four species, and one laboratory strain, P. gingivalis W83, were examined. Eleven of the 12 strains displayed heterogeneity with respect to pH-dependent zeta potentials. Within single cultures of each of these strains, two distinct populations of cells were found, one which was more negatively charged than the other. For the Gram-negative strains, the more negatively charged subpopulation was in the majority, while the P. micros strains appeared to be composed mainly of a less-negatively-charged subpopulation. Vesicles prepared from two strains displayed the same pH dependence and heterogeneity of zeta potentials as the parent cells. An A.a. strain which was passaged several times in fluid medium had lost its fimbriae and became homogeneous with respect to charge.

Aggregatibacter actinomycetemcomitans↗