Higher Bacterial Adhesion Research Articles

Does dental material type influence bacterial adhesion under the same polishing conditions? Direct observation using a fluorescent staining technique: An in vitro study.

Highly polished 3, 4, and 5 mol% yttria-stabilized zirconia and CAD/CAM composite resin samples were prepared, and the influence of surface roughness (Ra and Sa, 21 areas/group), wettability (contact angle and surface energy, 3 samples/group), and surface chemical composition (2 samples/group) on single-strain bacterial adhesion models (Porphyromonas gingivalis, Streptococcus oralis, Streptococcus sanguinis, Streptococcus gordonii, and Streptococcus mutans) were compared via fluorescent staining with graphical analysis (21 areas/group). Statistical analysis was performed using the Shapiro-Wilk test followed by one-way analysis of variance with Tukey's test or the Kruskal-Wallis test with Dunn's test (α=0.05) and linear regression. For dental zirconia with the same surface roughness, the yttria content did not significantly influence the initial bacterial adhesion. However, higher bacterial adhesion was detected for the composite resin owing to its high C, O, and Si contents. There was no correlation between surface energy and bacterial adhesion for any bacterial strain (p<0.005).

Leaching-Free durable antibacterial composite films constructed via delicate balance between potent contact sterilization and low adhesion

Durable antibacterial surfaces are often required high bactericidal ability and low bacterial adhesion property, but the potent bactericidal surfaces, especially based on the contact bactericidal mechanism, are often paradoxically intended to attract bacteria to adhere. In this work, a delicate balance between the potent contact bactericidal action and low bacterial adhesion was successfully achieved in quaternized fluoropolymer/SiO2 composite films (QFP/SiO2 CFs) through judicious selection of a common fluorinated monomer, a common quaternary ammonium monomer, and a common inert inorganic nanoparticle, to acquire suitable surface energy and chain mobility to ensure low bacterial adhesion, as well as to allow appropriate surface-exposed quaternary ammonium units to synergistically enhance the contact bactericidal action with the specific fluorinated side chains. The QFP/SiO2 CFs were conveniently fabricated through miniemulsion polymerization and followed squeegeeing technique. The QFP/SiO2 CF with an optimized composition exhibited extremely low initial adhesion of bacteria, potent contact bactericidal action, superior long-term antibacterial performance, easy sonication-assistant regeneration for multiple usage, and low cytotoxicity with non-leachable attribute. This work may guide the design and efficient fabrication of leaching-free durable antibacterial surfaces for biological applications, as well as provide an effective strategy to balance contact bactericidal action and low bacteria adhesion for durable antibacterial performance.

High-flux bacterial cellulose ultrafiltration membrane with controllable pore structure

Nanocellulose membranes have attracted widespread attention because of its nano pore size, environmental friendliness, hydrophilicity and biocompatibility. However, the low water permeation, weak wet strength and high bacterial adhesion limit their pratical application. Herein, an ultrafiltration membrane based on bacterial cellulose (BC) with high flux, high wet strength and antibacterial property was prepared by using nano silica as porogen and polyhexamethylene guanidine hydrochloride (PHGHE) as both crosslinker and fungicide. Without affecting the uniformity of the membrane, a high dosage of nano silica was conducted to construct straight-through channels in the membrane Z direction, which greatly reduces the actual capillary tube length and increases the flux. The effective pore size was successfully controlled below 90 nm and the flux reached a high level of 7147 L·m−2·h−1·bar−1. After PHGHE modification, the wet strength of the BC membrane increased by 4.5 times (up to 4.47 MPa) as well as significantly improved the antibacterial performance (zone of inhibition=15.0–15.2 mm). The underwater superoleophobicity and nanoscale pore size make it excellent at separating nanoparticles and nanoemulsions with sizes even lower than 100 nm in aqueous solutions. The developed high flux BC membrane would have wide applications in wastewater separation and purification.

Synthesis of self-cleaning and photoreactive spherical layered double oxide/polymer composite thin layers: Biofouling and inactivation of bacteria

Layered double oxide (LDO) photocatalyst microparticles were synthetized with special radial lamellar orientation. We presented that the 25.31 ± 2.34 μm LDO particles with rough surface can incorporated in fluoropolymer solution and resulted a composite layer with dual superhydrophobic and photocatalytic properties with high bacterial adhesion and inactivation ability. Next the LDO content in the composite layers were systematically increased (0, 20, 40, 60, 80 and 100 wt% LDO) which facilitated the surface adhesion of bacteria by electrostatic interactions. The structure of the initial LDO and LDO/fluoropolymer composites was verified by small angle X-ray scattering (SAXS), XRD and SEM measurements. We showed that the surface roughness and hydrophobicity increase with increasing LDO loading. At 80/20 wt% LDO/fluoropolymer ratio the apparent surface energy was low enough to obtain a superhydrophobic surface (θw= 156.3° and γstot= 2.7 mJ/m2). The bacterial adhesion extent on LDO/fluoropolymer composite layers increases with increasing LDO content because the adhesion takes place preferentially to LDO lamellae. The reason for this pronounced adhesion of negatively charged and hydrophilic bacteria onto positively charged and hydrophilic LDO surfaces is the electrostatic attraction between oppositely charged surfaces. The bacterial adhesion was detected by scanning electron and fluorescence microscopy and crystal violet staining assay. Finally, the adhered bacteria were inactivated by the LED-light illumination due to photoreactivity of LDO particles containing 12 wt% of ZnO phase.

Partially Melted Ti6Al4V Particles Increase Bacterial Adhesion and Inhibit Osteogenic Activity on 3D-printed Implants: An In Vitro Study.

A porous Ti6Al4V implant that is manufactured using selective laser melting (SLM) has broad potential applications in the field of orthopaedic implants. The pore structure of the SLM porous Ti6Al4V implant allows for cell migration and osteogenic differentiation, which is favorable for bone ingrowth and osseointegration. However, it is unclear whether the pore structure and partially melted Ti6Al4V particles on a SLM porous Ti6Al4V implant will increase bacterial adhesion and, perhaps, the risk of implant-related infection. (1) Is there more bacterial adhesion and colonization on SLM porous Ti6Al4V implants than on polished orthopaedic implants? (2) Do partially melted Ti6Al4V particles on SLM porous Ti6Al4V implants reduce human bone mesenchymal stem cells (hBMSCs) adhesion, viability, and activity? To determine bacterial adhesion and biofilm formation, we incubated five different Ti6Al4V discs (polished, grit-blasted, plasma-sprayed, particle SLM porous, and nonparticle SLM porous discs) with methicillin-resistant Staphylococcus aureus (MRSA) and Escherichia coli. Bacterial coverage on the surface of the five different Ti6Al4V discs were evaluated based on scanning electron microscopy (SEM) images quantitatively. In addition, a spread-plate method was used to quantitatively evaluate the bacterial adhesion on those implants. The biofilm formation was stained with crystal violet and semi-quantitatively determined with a microplate reader. The morphology and adhesion of hBMSCs on the five Ti6Al4V discs were observed with SEM. The cell viability was quantitatively evaluated with a Cell Counting Kit-8 assay. In addition, the osteogenic activity was determined in vitro with a quantitatively alkaline phosphatase activity assay and alizarin-red staining. For semiquantitative analysis, the alizarin-red stained mineralized nodules were dissolved and determined with a microplate reader. The polished discs had the lowest MRSA adhesion (8.3% ± 2.6%) compared with grit-blasted (19.1% ± 3.9%; p = 0.006), plasma-sprayed (38.5% ± 5.3%; p < 0.001), particle (23.1% ± 2.8%; p < 0.001), and nonparticle discs (15.7% ± 2.5%; p = 0.003). Additionally, when comparing the two SLM discs, we found that particle discs had higher bacterial coverage than nonparticle discs (23.1% ± 2.8% versus 15.7% ± 2.5%; p = 0.020). An E. coli analysis showed similar results, with the higher adhesion to particle SLM discs than to nonparticle discs (20.7% ± 4.2% versus 14.4% ± 3.6%; p = 0.011). In addition, on particle SLM porous discs, bacterial colonies were localized around the partially melted Ti6Al4V particles, based on SEM images. After a 7-day incubation period, the cell viability in the particle group (optical density value 0.72 ± 0.05) was lower than that in the nonparticle groups (optical density value: 0.87 ± 0.08; p = 0.003). Alkaline phosphatase activity, as a marker of osteogenic differentiation, was lower in the particle group than in the nonparticle group (1.32 ± 0.12 U/mL versus 1.58 ± 0.09 U/mL; p = 0.012). Higher bacterial adhesion was observed on SLM porous discs than on polished discs. The partially melted Ti6Al4V particles on SLM porous discs not only enhanced bacterial adhesion but also inhibited the osteogenic activity of hBMSCs. Postprocessing treatment is necessary to remove partially melted Ti6Al4V particles on an SLM implant before further use. Additional studies are needed to determine whether an SLM porous Ti6Al4V implant increases the risk of implant-related infection in vivo. As implants with porous Ti6Al4V made using SLM are being designed, our preliminary findings suggest that postprocessing treatment is needed to remove partially melted Ti6Al4V particles before further use. In addition, the depth of the porous structure of the SLM implant should not exceed the maximum depth of bone ingrowth because the host immune defense cannot prevent bacterial adhesion without integration.

Novel tape-cast SiOC-based porous ceramic electrode materials for potential application in bioelectrochemical systems

One alternative to improve electrochemical performance and long-term applicability in microbial bioelectrochemical systems (BESs) is the use of porous ceramic electrodes. In this work, electrodes of polymer-derived ceramics based on poly(silsesquioxanes) are synthesized, tailoring the properties by varying pyrolysis temperatures and incorporating conductive phases. Carbon (graphite, carbon black) and metal-based (stainless steel/Cu grids, Co/Ni particles) materials are incorporated into the silicon oxycarbide (SiOC) matrix. The influence of pyrolysis temperature and incorporation of conductive materials on functional properties and electrical conductivity is discussed. Furthermore, this study provides the first investigation of biofilm development on SiOC-based ceramic surfaces with Escherichia coli and Bacillus cereus. SiOC-based ceramics with DC conductivity values at room temperature in the semiconductor range (0.044–0.385 S cm−1) were obtained, with the highest values achieved by Co and Ni particles incorporation and in situ formation of CNTs. Adjustment in hydrophilicity and specific surface areas (6.21–263.45 m2 g−1) is realized by the pyrolysis. The biofilm studies reveal adhesion in the first 2 h for most of the surfaces, with higher bacterial adhesion and biofilm formation with the E. coli. The biocompatibility in terms of bacterial attachment and conductivity values comparable to a commercial carbon felt support the applicability of the developed SiOC-based materials as promising new class of electrodes for BES.

Flexible mechanoprosthesis made from woven ultra-high-molecular-weight polyethylene fibres: proof of concept in a chronic sheep model.

Ultra-high-molecular-weight polyethylene (UHMWPE) fibres are flexible, have high tensile strength, and platelet and bacterial adhesion is low. Therefore, UHMWPE may overcome limitations of current mechanical valves and bioprostheses. In this study, the biocompatibility and functionality of prototype handmade stented valves from woven UHMWPE (U-valve) was assessed in a chronic sheep model with acetylsalicylic acid monotherapy. Native pulmonary valves of 23 sheep were replaced by U-valves (n = 18) or Perimount bovine bioprostheses (reference group, n = 5). Sheep received 80 mg of acetylsalicylic acid daily. Follow-up was conducted at 1 week (n = 4), 1 month (n = 5), 3 months (n = 5) and 6 months (n = 4) in the U-valve group and at 3 months (n = 2) and 6 months (n = 3) in the reference group. Epicardial echocardiography and histology were used to assess valve function and tissue deposition, respectively. Seventeen U-valve sheep (94%) and 3 reference sheep (60%) survived the perioperative period. One reference valve sheep was sacrificed after 4 months because of congestive heart failure. At explantation, all U-valves were intact without leaflet tearing. Up to 3 months, U-valves were flexible and free of stenosis. Regurgitation was mostly mild though gradually increasing; histology showed minimal connective tissue near the leaflet base and sparse calcification. At 6 months, connective tissue was diffusely observed on the leaflets with retraction and consecutive regurgitation and leaflet thickening. Valves made from UHMWPE fibres demonstrated early feasibility in the pulmonary valve position with reasonably good haemodynamics and intact valve materials up to 6 months. Gradual leaflet thickening and retraction were observed after 3 months due to connective tissue overgrowth.

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

BackgroundThis 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.MethodsZirconia 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 (Ra) 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.ResultsVariations in surface roughness (Ra) did not lead to any differences in adhering S. epidermidis, but higher Ra 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.ConclusionsBoth 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 Ra (measured by stylus profilometer) are inadequate for describing surface roughness with regard to its potential influence on microbial adhesion.

Evaluation of Surface Roughness and Bacterial Adhesion on Tooth Enamel Irradiated With High Intensity Lasers.

The aim was to evaluate the surface roughness and bacterial adhesion on enamel irradiated with high intensity lasers, associated or not to a fluoride varnish. Eighty fragments of bovine enamel were equally divided in 8 groups (n=10). Group 1 was not treated and Group 2 received only a 5% fluoride varnish application. The other groups were irradiated with an Er:Cr:YSGG (8.92 J/cm2), an Nd:YAG (84.9 J/cm2) and a diode laser (199.04 J/cm2), associated or not to a 5% fluoride varnish. The surface roughness was measured before and after treatments. Afterward, all samples were incubated in a suspension of S. mutans at 37 °C for 24 h. The colony-forming units (CFU) were counted by a stereoscope and the results were expressed in CFU/mm2. One-way ANOVA and the Tukey´s test compared the roughness data and the Student´s test compared the results obtained in the bacterial adhesion test (a=5%). The results showed that the irradiated samples without varnish presented the same roughness and the same bacterial adhesion that the non-irradiated samples. However, samples irradiated in the presence of fluoride varnish showed higher surface roughness and higher bacterial adhesion than the non-irradiated samples and those irradiated without varnish. Presence of pigments in the varnish increased the lasers' action on the enamel surface, which produced ablation in this hard tissue and significantly increased its surface roughness. For this reason, the enamel's susceptibility to bacterial adhesion was higher when the irradiation of the samples was made in presence of fluoride varnish.

Inhibition of bacterial adhesion and biofilm formation by antimicrobial functionalized textured biomaterial surfaces

Event Abstract Back to Event Inhibition of bacterial adhesion and biofilm formation by antimicrobial functionalized textured biomaterial surfaces Lichong Xu1, Yaqi Wo2, Mark E. Mayerhoffb2, Zhicheng Tian3, Harry Allcock3 and Christopher A. Siedlecki1, 4 1 Penn State College of Medicine, Department of Surgery, United States 2 University of Michigan, Department of Chemistry, United States 3 The Pennsylvania State University, Department of Chemistry, United States 4 Penn State College of Medicine, Department of Bioengineering, United States Introduction: Infection due to bacterial adhesion and biofilm formation represetns a major drawback to the use of blood-contacting devices. Previously we have developed textured polyurethane biomaterials for reducing bacterial adhesion and inhibiting biofilm formation. In this work, we applied the texturing pattern to functionalized polymers bearing antimicrobial properties, and show a combination of antimicrobial functionalization and physical approaches can produce additive effects on biological responses and enhance the hemocompatibility of biomaterials. Material and Methods: Carbosil polyurethane (PU, 2080A) and phosphazene polymers (trifluoroethoxy (TFE), crosslinakble trifluoroethoxy (XLTFE), and octafluoropentoxy (OFP)) were textured with ordered arrays of pillars using a soft lithography two-stage replication molding technique[1]. The Carbosil polyurethane material was doped with S-nitroso-N-acetylpenicillamine (SNAP) with different contents of SNAP in PU (5, 10, and 15 wt%) for nitric oxide (NO) release[2]. Antimicrobial properties of materials were evaluated by the optical density (OD600) of microbial cultures incubated with materials and strain S. epidermidis RP62A. Bacterial adhesion and biofilm formation on material surfaces were carried out in a multiwell plate or rotating disk system (RDS)[1] with same strain. Bacterial adhesion was counted under a fluorescent optical microscope. To observe biofilm formation, samples were in incubated in multiwell plates under static condition for 2 days or RDS system under shear for 8 days. Samples were stained with FTIC conjugated wheat germ agglutinin, and biofilm observed by fluorescence. Results and Discussion: Characterization of biomaterial surfaces: AFM images showed material surfaces textured with ordered arrays of pillars, as expected, except for TFE and XLTFE materials that were difficult to texture.Water contact angle measurements show surface hydrophobicity increased after texturing due to entrapped air. Antimicrobial properties of materials:The optical densities of culture media indicate the growth of bacteria in the presence of a variety of polymers (Fig. 1). Carbosil PU 0% SNAP and PUU films show the similar optical density as that of control (no polymers). Significant inhibition of bacterial growth was observed in the cultures for Carbosil 10% and 15% SNAP polymers, indicating NO release inhibits the growth of bacteria. A slight decrease of OD600 was observed for all phosphazene polymers. Fig. 1 Optical density of culture media indicating antimicrobial properties of polymers. Bacterial adhesion on functionalized textured polymer surfaces: Higher bacterial adhesion was observed on smooth surfaces without functionalization (Fig. 2). Surface texturing with pattern decreased bacterial adhesion on all surfaces, except for TFE and XLTFE polymers, indicating the importance of surface texturing in inhibiting adhesion. Furthermore, a significant decrease in adhesion was observed on textured PU surfaces containing 10% or 15% SNAP as well as on OFP textured surfaces, suggesting antimicrobial functionalization and texturing produce a synergistic effect on inhibiting bacterial adhesion, as the OFP polymer alone inhibited bacterial growth only slightly. Fig. 2 Bacterial adhesion on polymer surface in PBS for 1 hr at 37°C under static condition. Biofilm formation: Under static condition, biofilms were observed on Carbosil PU surfaces containing 0% SNAP and 5% SNAP after 2 days, while no biofilms were observed on surfaces containing 10% and 15% SNAP. Under shear stresses, no biofilms were observed on smooth or textured PU surfaces containing 15% SNAP after 8 days. Long term exposure experiments for biofilm formation on functionalized textured surfaces are on-going. Fig. 3 Biofilm on textured 500/500 nm patterned surfaces containing (a) 0% SNAP, (b) 15% SNAP under static condition for 2 days, and (c) 15% SNAP under shear for 8 days. Conclusion: A combination of antimicrobial functionalization of polymers and surface texturing provided an improved approach to inhibiting bacterial adhesion and biofilm formation, and thus to potentially preventing biomaterial related infections.

Study of Bacterial Adhesion on Biomimetic Temperature Responsive Glycopolymer Surfaces

Pseudomonas aeruginosa is an opportunistic pathogen responsible for diseases such as bacteremia, chronic lung infection, and acute ulcerative keratitis. P. aeruginosa induced diseases can be fatal as the exotoxins and endotoxins released by the bacterium continue to damage host tissues even after the administration of antibiotics. As bacterial adhesion on cell surfaces is the first step in bacterial based pathogen infections, the control of bacteria-cell interactions is a worthwhile research target. In this work, thermally responsive poly(N-isopropylacrylamide) [P(NIPAAm)] based biomimetic surfaces were developed to study the two major bacterial infection mechanisms, which is believed to be mediated by hydrophobic or lectin-carbohydrate interactions, using quartz crystal microbalance with dissipation. Although, a greater number of P. aeruginosa adhered to the NIPAAm homopolymer modified surfaces at temperatures higher than the lower critical solution temperature (LCST), the bacterium-substratum bond stiffness was stronger between P. aeruginosa and a galactose based P(NIPAAm) surface. The high bacterial adhesion bond stiffness observed on the galactose based thermally responsive surface at 37 °C might suggest that both hydrophobic and lectin-carbohydrate interactions contribute to bacterial adhesion on cell surfaces. Our investigation also suggests that the lectin-carbohydrate interaction play a significant role in bacterial infections.

The influence of surface modification on bacterial adhesion to titanium-based substrates.

This study examines bacterial adhesion on titanium-substrates used for bone implants. Adhesion is the most critical phase of bacterial colonization on medical devices. The surface of titanium was modified by hydrothermal treatment (HT) to synthesize nanostructured TiO2-anatase coatings, which were previously proven to improve corrosion resistance, affect the plasma protein adsorption, and enhance osteogenesis. The affinity of the anatase coatings toward bacterial attachment was studied by using a green fluorescent protein-expressing Escherichia coli (gfp-E. coli) strain in connection with surface photoactivation by UV irradiation. We also analyzed the effects of surface topography, roughness, charge, and wettability. The results suggested the dominant effects of the macroscopic surface topography, as well as microasperity at the surface roughness scale, which were produced during titanium machining, HT treatment, or both. Macroscopic grooves provided a preferential site for bacteria deposit within the valleys, while the microscopic roughness of the valleys determined the actual interaction surface between bacterium and substrate, resulting in an "interlocking" effect and undesired high bacterial adhesion on nontreated titanium. In the case of TiO2-coated samples, the nanocrystals reduced the width between the microasperities and thus added nanoroughness features. These factors decreased the contact area between the bacterium and the coating, with consequent lower bacterial adhesion (up to 50% less) in comparison to the nontreated titanium. On the other hand, the pronounced hydrophilicity of one of the HT-coated discs after pre-irradiation seemed to enhance the attachment of bacteria, although the increase was not statistically significant (p > 0.05). This observation may be explained by the acquired similar degree of wetting between gfp-E. coli and the coating. No correlation was found between the bacterial adhesion and the ζ-values of the samples in PBS, so the effect of surface charge was considered negligible in this study.

High antibacterial efficiency of pDMAEMA modified silicon nanowire arrays

Materials of high antibacterial activity based on quaternized poly (2-(dimethylamino ethyl) methacrylate) (pDMAEMA) have been developed. DMAEMA was graft polymerized on silicon nanowire arrays (SiNWAs) by atom transfer radical polymerization (ATRP), and quaternized using benzyl chloride. The graft density on the modified nanowire arrays was much higher than on analogous smooth silicon, leading to higher bacterial adhesion on the nanowire arrays (34.6±0.39×106 vs. 5.0±0.15×106cells/cm2). Incubation of Escherichia coli on the substrates for 18h resulted in 95% cell death on the quaternized nanowire material compared to less than 45% on the quaternized smooth silicon. The results suggest that silicon nanowire array modified with quaternized pDMAEMA is a highly effective antibacterial material due to a high density of antibacterial polymer and consequent high bacterial adhesion and killing.

Fabrication of microtemplates for the control of bacterial immobilization

The authors described a region-selective immobilization methods of bacteria by using superhydrophobic/superhydrophilic and superhydrophobic/poly(ethylene glycol) (PEG) micropatterns for culture scaffold templates. In the case of superhydrophobic/superhydrophilic micropatterns, the superhydrophobic surface was prepared first by microwave-plasma enhanced chemical vapor deposition (MPECVD) from trimethylmethoxysilane. Then the superhydrophilic regions were fabricated by irradiating the superhydrophobic surface with vuv light through a stencil mask. In the case of the superhydrophobic/PEG micropatterned surfaces, PEG surfaces were fabricated first by chemical reaction of ester groups of p-nitrophenyl PEG with NH2 group of NH2-terminated self assembled monolayer from n-6-hexyl-3-aminopropyltrimethoxysilane. The superhydrophobic regions were fabricated by MPECVD thorough a stencil mask. In this study four bacteria were selected from viewpoint of peptidoglycan cell wall (E. coli versus B. subtilis), extracellular polysaccharide (E.coli versus P. stutzeri, P. aeruginosa), and growth rate (P. stutzeri versus P. aeruginosa). The former micropattern brought discrete adhesions of E. coli and B. subtilis specifically on the hydrophobic regions, Furthermore, using the superhydrophobic/PEG micropattern, adhesion of bacteria expanded for E. coli, B. subtilis, P. stutzeri, and P. aeruginosa. They observed a high bacterial adhesion onto superhydrophobic surfaces and the inhibitive effect of bacterial adhesion on PEG surfaces.

Adhesion of Streptococcus mutans to various dental materials in a laminar flow chamber system

Newly developed dental materials have to be tested for their susceptibility to adhere bacteria causing caries and periodontitis. The objective of this study was to establish an in vitro laminar flow chamber assay for dental material evaluation with regard to the adhesion of oral bacteria. Test specimens of commonly used dental materials (ceramic (five brands of ceramics, n = 15/brand), composite (eight brands of composites, n = 15/brand), and alloy (two brands of alloys, n = 15/brand) specimens) were inserted in a laminar flow chamber system and rinsed with artificial saliva (2 h) and Streptococcus mutans NCTC 10,449 suspension (4 h) successively. The amount of adhered bacteria was quantified using a Resazurin reduction assay (Alamar Blue). Statistical analysis was performed using the Mann-Whitney U-test (alpha = 0.05). Regarding adhesion of Streptococcus mutans, significant differences between the various material classes were found. Highest fluorescence values (ranging from 973 to 3145), correlating with high bacterial adhesion, were found on composite samples, and lowest values (173-272) were found on the alloys. Ceramic specimens showed an intermediate adhesion of Streptococcus mutans (fluorescence values from 532 to 1326). Streptococcus mutans NCTC 10449 adhered differently to the various classes of dental materials. The established laminar flow chamber device provides a suitable method for evaluating the adhesion of oral bacteria to dental material surfaces.

Bacterial adhesion to and viability on positively charged polymer surfaces

Secondary and tertiary amino groups were introduced into polymer chains grafted onto a polyethylene flat-sheet membrane to evaluate the effects of surface properties on the adhesion and viability of a strain of the Gram-negative bacterium Escherichia coli and a strain of the Gram-positive bacterium Bacillus subtilis. The characterization of the surfaces containing amino groups, i.e. ethylamino (EA) and diethylamino (DEA) groups, revealed that the membrane potentials are proportional to amino-group densities and contact angle hysteresis. A high bacterial adhesion rate constant k was observed at high membrane potential, which indicates that membrane potential could be used as an indicator for estimating bacterial adhesion to the EA and DEA sheets, especially in B. subtilis. The bacterial adhesion rate constant of E. coli markedly increased at a membrane potential higher than -7.8 mV, whereas that of B. subtilis increased at a membrane potential higher than -8.3 mV, at which the dominant effect on bacterial adhesion is expected to change. The viability experiments revealed that approximately 80% of E. coli cells adhering to the sheets with high membrane potential were inactivated after a contact time of 8 h, whereas 60% of B. subtilis cells were inactivated. Furthermore, E. coli viability significantly decreased at a membrane potential higher than -8 mV, whereas B. subtilis viability decreased as membrane potential increased, which reflects differences in cell wall structure between E. coli and B. subtilis.