Epidermidis Adhesion Research Articles

Porous titanium scaffolds modified with Zeolitic Imidazolate Framework (ZIF-8) with enhanced osteogenic activity for the prevention of implant-associated infections.

In this study, zeolitic imidazolate framework 8 (ZIF-8) was coated on porous Ti6Al4V scaffolds, either bare or previously modified using hydroxyapatite (HA) or HA and gelatin (HAgel), via a growing single-step method in aqueous media using two contact times at 6h and 24h. The coated scaffolds termed ZIF-8@Ti, ZIF-8@HA/Ti, and ZIF-8@HAgel/Ti were characterized via scanning electron microscopy (SEM), powder X-ray diffraction (PXRD), attenuated total reflectance-Fourier transform infrared (ATR-FTIR), and molecular plasma-atomic emission spectroscopy (MP-AES). In order to assess the cell proliferation rate, the cytocompatibility of the scaffolds was evaluated in primary osteoblasts (hOBs) using alamarBlue assay, while the osteoconductivity was analyzed in hOBs using a real-time approach, evaluating the expression of secreted phosphoprotein 1 (SPP1). Osteopontin, which is the protein encoded by this gene, represents the major non-collagenous bone protein that binds tightly to HA. The scaffolds were shown to be non-cytotoxic based on hOB proliferation at all time points of analysis (24h and 72h). In hOB cultures, the scaffolds induced the upregulation of SPP1 with different fold changes. Some selected scaffolds were assayed in vitro for their antibacterial potential against Staphylococcus epidermidis; the scaffolds coated with ZIF-8 crystals, regardless of the presence of HA and gelatin, strongly inhibited bacterial adhesion to the materials and reduced bacterial proliferation in the culture medium, demonstrating the suitable release of ZIF-8 in a bioactive form. These experiments suggest that the innovative scaffolds, tested herein, provide a good microenvironment for hOB adhesion, viability, and osteoconduction with effective prevention of S. epidermidis adhesion.

The giant staphylococcal protein Embp facilitates colonization of surfaces through Velcro-like attachment to fibrillated fibronectin

Staphylococcus epidermidis causes some of the most hard-to-treat clinical infections by forming biofilms: Multicellular communities of bacteria encased in a protective matrix, supporting immune evasion and tolerance against antibiotics. Biofilms occur most commonly on medical implants, and a key event in implant colonization is the robust adherence to the surface, facilitated by interactions between bacterial surface proteins and host matrix components. S. epidermidis is equipped with a giant adhesive protein, extracellular matrix-binding protein (Embp), which facilitates bacterial interactions with surface-deposited, but not soluble fibronectin. The structural basis behind this selective binding process has remained obscure. Using a suite of single-cell and single-molecule analysis techniques, we show that S. epidermidis is capable of such distinction because Embp binds specifically to fibrillated fibronectin on surfaces, while ignoring globular fibronectin in solution. S. epidermidis adherence is critically dependent on multivalent interactions involving 50 fibronectin-binding repeats of Embp. This unusual, Velcro-like interaction proved critical for colonization of surfaces under high flow, making this newly identified attachment mechanism particularly relevant for colonization of intravascular devices, such as prosthetic heart valves or vascular grafts. Other biofilm-forming pathogens, such as Staphylococcus aureus, express homologs of Embp and likely deploy the same mechanism for surface colonization. Our results may open for a novel direction in efforts to combat devastating, biofilm-associated infections, as the development of implant materials that steer the conformation of adsorbed proteins is a much more manageable task than avoiding protein adsorption altogether.

Nanostructured Titanium for Improved Endothelial Biocompatibility and Reduced Platelet Adhesion in Stent Applications

Although coronary stents have improved the early and long-term consequences of arterial lesions, the prevention of restenosis and late stent thrombosis is key to prevent a new obstruction of the vessel. Here we aimed at improving the tissue response to stents through surface modification. For that purpose, we used two different approaches, the use of nanostructuration by electrochemical anodization and the addition of a quercitrin (QR) coating to the Ti surface. Four surfaces (Ti, NN, TiQR and NNQR) were characterized by atomic force microscopy, scanning electronic microscopy and contact angle analysis and QR content was evaluated by fluorescent staining. Cell adhesion, cytotoxicity, metabolic activity and nitric oxide (NO) production was evaluated on primary human umbilical cord endothelial cells (HUVECs). Platelet adhesion, hemolysis rate and Staphylococcus epidermidis CECT 4184 adhesion at 30 min were analyzed. Nanostructuration induced an increase on surface roughness, and QR coating decreased the contact angle. All surfaces were biocompatible, with no hemolysis rate and lower platelet adhesion was found in NN surfaces. Finally, S. epidermidis adhesion was lower on TiQR surfaces compared to Ti. In conclusion, our results suggest that NN structuration could improve biocompatibility of bare metal stents on endothelial cells and reduce platelet adhesion. Moreover, QR coating could reduce bacterial adhesion.

Hyaluronic Acid Reduces Bacterial Fouling and Promotes Fibroblasts' Adhesion onto Chitosan 2D-Wound Dressings.

Wound healing is a dynamic process that can be seriously delayed by many factors including infectious complications. The development of dressings with intrinsic wound healing activity and/or releasing bioactive compounds may help with addressing such an issue. In this study, hyaluronic acid (HA) at different percentages (1–35%) was used to modify chitosan (CS) biological and physico-chemical properties in order to obtain 2D-matrices able to promote healing and protect from infection. HA incorporation in the CS matrix decreased film transparency and homogeneity, but improved film water uptake and surface wettability. The water vapor transmission rate (WVTR) increased up to a 5% HA content, where it reached the highest value (672 g/m2 day), and decreased for higher HA contents. At all of the tested HA concentrations, HA affected mechanical properties providing matrices more flexible than pure CS with benefit for wound care. Pure CS films permitted S. epidermidis adhesion and biofilm formation. That was not true for CS/HA matrices, where HA at concentrations equal to or greater than 5% was able to avoid S. epidermidis adhesion. Fibroblasts adhesion also took benefit from the HA presence in the film, especially at 5% content, where the best adhesion and proliferation was found.

Quebrachitol from Rhizophora mucronata inhibits biofilm formation and virulence production in Staphylococcus epidermidis by impairment of initial attachment and intercellular adhesion

Staphylococcus epidermidis is well recognized nosocomial pathogen in clinical settings for their implants associated infections. Biofilm and virulence production executes a S. epidermidis pathogenesis against host. Hence, interfering of biofilm formation has become an auspicious to control the pathogenesis of S. epidermidis. The present study evaluates antibiofilm potential of Rhizophora mucronata against S. epidermidis biofilms. Rhizophora mucronata leaves extract significantly inhibited the biofilm formation and quebrachitol was identified as an active compound responsible for the biofilm inhibition. Quebrachitol significantly inhibited biofilm formation at concentration dependent manner without exhibit non-bactericidal property. And, quebrachitol reduced the biofilm building components such as exopolysaccharides, lipase and proteins production. Confocal laser scanning microscopic studies obtained quebrachitol surface independent biofilm efficacy against S. epidermidis. Notably, quebrachitol significantly reduced S. epidermidis adherence on biotic (coated with type I collagen and fibrinogen) and abiotic (hydrophobic and hydrophilic) surfaces. Addition of quebrachitol inhibits autolysis mediated initial attachment and accumulation associated aggregation process. Moreover, quebrachitol significantly reduced the hydrolases virulence production which supports S. epidermidis invasion into the host. Furthermore, gene expression analysis revealed the ability of quebrachitol to downregulate the virulence genes expression which are mainly involved in biofilm formation and virulence production. The results obtained from the present study suggest that quebrachitol as an ideal candidate for the therapeutic action against S. epidermidis pathogenesis.

Effectiveness of manual versus automated cleaning on Staphylococcus epidermidis biofilm removal from the surface of surgical instruments

Biofilm removal is a challenge during surgical instrument processing. We analyzed the time required for Staphylococcus epidermidis to form biofilms on surgical instruments, and how cleaning methods removed them. Different areas (ratchet, shank, and jaw) of straight crile forceps were contaminated by soaking in Tryptic Soy Broth containing 106 colony forming units (CFU)/mL of S epidermidis for 1, 2, 4, 6, 8, and 12 hours. S epidermidis adhesion and removal, after manual or automated ultrasonic cleaning, was evaluated by microbiological culture and scanning electron microscopy. Microbial load increased with time (101-102 CFU/cm2 after 1 hour; 104 CFU/cm2 after 12 hours). Exopolysaccharide was detected after 2 hours and gradually increased thereafter. Bacterial load was reduced by 1-2 log10 after manual cleaning and 1-3 log10 after automated cleaning, but biofilms were not completely eliminated. In general, bacterial load was lower in shank fragments. This difference was significant at 6 hours. Rapid adhesion of S epidermidis and exopolysaccharide formation was observed on surgical instruments. Automated cleaning was more effective than manual cleaning, but neither method removed biofilms completely. The precleaning conditions and the forceps design are critical factors in processing quality.

Biofilm prevention by dicephalic cationic surfactants and their interactions with DNA.

The studies were aimed to contribute to the elucidation of the relationships between structure of the double-headed cationic surfactants-N,N-bis[3,3'-(dimethylamine)- propyl]alkylamide dihydrochlorides and N,N-bis[3,3'-(trimethylammonio)propyl]alkylamide dibromides (alkyl: n-C9 H19 , n-C11 H23 , n-C13 H27 , n-C15 H31 ) and their antibacterial and biofilm preventing activity. The minimal inhibitory and bactericidal concentrations (MIC and MBC) of dicephalic surfactants against Staphylococcus epidermidis and Pseudomonas aeruginosa were tested using standard methods. Pseudomonas aeruginosa was resistant to studied compounds but MBC values against Staph.epidermidis reached 0·48-0·01mmoll(-1) . The influence of dicephalic surfactants on bacterial biofilm and adhesion to the various surfaces was investigated with crystal violet staining or colony counting. The reduction in bacterial adhesion was observed, especially in the case of glass and stainless steel. The condensation of the DNA was shown in the ethidium bromide intercalation assay. Dicephalic surfactants exhibited antibacterial activity against Staph.epidermidis. The activity of studied compounds depended on the hydrocarbon chain length and the counterion. Surfactants deposited on different materials reduced Staph.epidermidis adhesion, dependently on the surfactant structure and the substratum. Dicephalic surfactants showed the ability of DNA compaction. This study points the possibility of application of dicephalic surfactants as the surface-coating agents to prevent biofilm formation. These compounds efficiently condensed DNA and are potential candidates for further studies towards the transfection.

In vitro evaluation of E. coli and S. epidermidis adhesion on dressing materials used in hypospadias repair

An in vitro study was performed to evaluate the adherence of Escherichia coli and Staphylococcus epidermidis to different dressing materials. Hydrophyl gauze swab (GS), sterile flax swab (FS), and their nitrofurazone (Furacin®) absorbed forms (GSF and FSF), sterile paraffin-covered gauze with chlorhexidine acetate (0.5 %) (Bactigrass®, BG), and semipermeable transparent film gauze (Tegaderm®, TG) were used in the study. A 1 cm2 of each material was placed in culture plates, and E. coli ATCC 25922 and S. epidermidis ATCC 12228 were suspended in each plate. After 24, 48 h, and 1 week of incubation period, colony counts were calculated in colony-forming units (CFU) per square centimeter unit. Bacterial adhesion was compared between groups, and each dressing material was also compared for different incubation periods (24, 48 h, and 1 week). The colony counts were significantly decreased in GSF and FSF groups (Kruskal–Wallis test, p 0.05). The significant difference detected for S. epidermidis adhesion in the first 24 to 48 h could not be detected at the end of a 1-week period. There was no statistical difference in groups when compared for 24-, 48-h, and 1-week periods of incubations (Wilcoxon signed-rank test, p > 0.05). In BG group, E. coli adhesion was increased, and S. epidermidis adhesion was decreased without a significant difference at the end of a 1-week period (p > 0.05). Nitrofurazone absorbed sterile gauze materials have less bacterial adhesion. In vitro adhesion of E. coli and S. epidermidis did not differ between the 24-h and 1-week period. E. coli adhesion to BG can be increased if the duration of dressing prolonged up to a 1-week period.Level of Evidence: Not ratable.

Bacterial adhesion to orthopaedic implant materials and a novel oxygen plasma modified PEEK surface

Despite extensive use of polyetheretherketone (PEEK) in biomedical applications, information about bacterial adhesion to this biomaterial is limited. This study investigated Staphylococcus aureus and Staphylococcus epidermidis adhesion to injection moulded and machined PEEK OPTIMA® using a custom-built adhesion chamber with medical grade titanium and Thermanox for comparison. Additionally, bacterial adhesion to a novel oxygen plasma modified PEEK was also investigated in both a pre-operative model in physiological saline, and additionally in a post-operative model in human blood plasma.In the pre-operative model, the rougher machined PEEK had a significantly greater number of adherent bacteria compared to injection moulded PEEK. Bacterial adhesion to titanium and Thermanox was similar. Oxygen plasma surface modification of PEEK did not lead to a significant change in bacterial adhesion in the pre-operative contamination model, despite observed changes in surface characteristics. In the post-operative contamination model, S. aureus adhesion was increased from 5×105CFUcm−2 to approximately 1.3×107CFUcm−2 on the modified surfaces due to differential protein adhesion during the conditioning period. However, S. epidermidis adhesion to modified PEEK was less than to unmodified PEEK in the post-operative model. These results illustrate the importance of testing bacterial adhesion of several strains in both a pre-operative and post-operative, clinically relevant bacterial contamination model.

Staphylococcus epidermidis Biofilm Formation and Structural Organization on Different Types of Intraocular Lenses under in vitro Flow Conditions

Aim: To compare the adherence and structural organization of Staphylococcus epidermidis biofilm on intraocular lenses (IOLs). Methods: IOLs made of 3 different biomaterials [polymethyl methacrylate (PMMA), hydrophilic acrylic or hydrophobic acrylic] were incubated into an S. epidermidis bacterial solution. Scanning electron microscopy was used to count the bound bacteria and to analyze the structural biofilm architecture. Results: After 4-6 h of incubation, adherence was statistically weakest on the hydrophilic acrylic polymer. On the hydrophobic acrylic material, the bacterial cells tended to cover the substratum in a horizontal spread in a continuous monolayer. On the hydrophilic acrylic material or on the PMMA material bacterial cells tended to form only few, small scattered cell clusters. Conclusions: The data suggest that the pattern of S. epidermidis adhesion varies with the IOL biomaterial. Hydrophobic IOLs seem to be more permissive to S. epidermidis adhesion.

The role of ionic interactions in the adherence of theStaphylococcus epidermidisadhesin SdrF to prosthetic material

Staphylococcus epidermidis infections are common complications of prosthetic device implantation. SdrF, a surface protein, appears to play a critical role in the initial colonization step by adhering to type I collagen and Dacron™. The role of ionic interactions in S. epidermidis adherence to prosthetic material was examined. SdrF was cloned and expressed in Lactococcus lactis. The effect of pH, cation concentration, and detergents on adherence to different types of plastic surfaces was assessed by crystal violet staining and bacterial cell counting. SdrF, in contrast with controls and other S. epidermidis surface proteins, bound to hydrophobic materials such as polystyrene. Binding was an ionic interaction and was affected by surface charge of the plastic, pH, and cation concentration. Adherence of the SdrF construct was increased to positively charged plastics and was reduced by increasing concentrations of Ca(2+) and Na(+). Binding was optimal at pH 7.4. Kinetic studies demonstrated that the SdrF B domain as well as one of the B subdomains was sufficient to mediate binding. The SdrF construct also bound more avidly to Goretex™ than the lacotococcal control. SdrF is a multifunctional protein that contributes to prosthetic devices infections by ionic, as well as specific receptor-ligand interactions.

Adhesion of Staphylococcus epidermidis to biomaterials is inhibited by fibronectin and albumin.

Decades of contradictory results have obscured the exact role of adsorbed fibronectin in the adhesion of the bacterium, Staphylococcus epidermidis, to biomaterials. Here, the ability of adsorbed fibronectin (FN) or bovine serum albumin (BSA) to modulate S. epidermidis adhesion to various biomaterials is reported. FN or BSA was adsorbed in increasing surface densities up to saturated monolayer coverage onto various common biomaterials, including poly(ethylene terephthalate), fluorinated ethylene propylene, poly(ether urethane), silicone, and borosilicate glass. Despite the wide range of surface characteristics represented, adsorption isotherms varied only subtly between materials for the two proteins considered. S. epidermidis adhesion to the various protein-coated biomaterials was quantified in a static-fluid batch adhesion assay. Although slight differences in overall adherent cell numbers were observed between the various protein-coated substrata, all materials exhibited significant dose-dependent decreases in S. epidermidis adhesion with increasing adsorption of either protein (FN, BSA) to all surfaces. Results here indicate that S. epidermidis adhesion to FN-coated surfaces is not a specific adhesion (i.e., receptor: ligand) mediated process, as no significant difference in adhesion was found between FN- and BSA-coated materials. Rather, results indicate that increasing surface density of either FN or BSA actually inhibited S. epidermidis adhesion to all biomaterials examined.

Inhibition de l’adhérence de Staphylococcus epidermidis sur des surfaces en titane par des polymères hydrosolubles bioactifs comportant des fonctions sulfonate, phosphate ou carboxylate

Implanted prostheses are sometimes subject to bacterial infections, which can threat their benefit rule on a long-term basis. Various methods are studied to fight against these infections. Among them, the grafting of bioactive polymers onto the prosthesis surface shows up as a promising way to the problem of infections. This work presents the influence of various water-soluble bioactive polymers on the inhibition of the Staphylococcus epidermidis adhesion on the titanium samples surfaces initially preadsorbed with various proteins. Whatever the studied protein is, it is shown that the bioactive polymer containing sulfonate functions generates an inhibition of the adhesion of Staphylococcus epidermidis. For a plasma preadsorption, the inhibition rate rises up to 68% when the concentration of sulfonate function is 2.5μmol/L. Titanium surfaces grafted with the bioactive polymer were also tested. We find an inhibitive activity of the adhesion close to that of the previous case. These preliminary results can point up a clinical interest in the fight against the medical devices infection, because they highlight a clear local effect of S. epidermidis adhesion inhibition. Copolymers containing other functional groups (phosphate or carboxylate) were dissolved in a bacterial suspension to monitor the influence of the composition on the adhesion inhibition. Their inhibition rates are not significantly lower than those of pNaSS homopolymers, as much as the sulfonate function proportion remains higher than 50%. Thus, the sulfonate function is the main responsible for the inhibition of the S. epidermidis adhesion.

Reply

We thank Dr. Esteban J. et al. for careful reading of our manuscript and for their comments that we would like to discuss. The recent article by Banche et al., based on an interdisciplinary approach, focused on strong integration between different research groups that shared their experience and knowledge in orthopedics, chemistry and microbiology, to elucidate the key role of biomaterial surface characteristics on microbial adhesion and biofilm formation. In details, the primary aim of this study was to evaluate the influence of different chemical surface features of some prosthetic polyethylenes (standard UHMWPE, oxidized UHMWPE, and vitamin E blended UHMWPE) on Staphylococcus epidermidis adhesion. coagulase-negative staphylococci, especially S. epidermidis, are opportunistic pathogens that mainly depend on the presence of indwelling foreign bodies to express their pathogenetic capacities in contrast to the more virulent S. aureus 1; S. epidermidis has been found to adhere more easily to polymers such as UHMWPE, whereas S. aureus more easily to metals 2; S. epidermidis is currently accepted as the most common cause of device related orthopedic infections, according to recent scientific literature 3-5; From 2000 to 2011 S. epidermidis has been isolated as frequently as S. aureus from BAI at the Department of Traumatology, Orthopaedics and Occupational Health (AO CTO/Maria Adelaide, Turin, Italy), where total joint replacements have been studied for many years; In the study we tested a clinical S. epidermidis strain recently isolated from an orthopedic implant infection (selected for its ability to establish clinically relevant infection on joint prosthesis) to compare its behavior with that of two laboratory ATCC S. epidermidis strains, chosen to allow the reproducibility of data. Our experimental studies required a well-characterized model with the number of uncontrolled parameters as small as possible in order to highlight the potential different effects exerted by three prosthetic polyethylenes. In addition, during the course of the adhesion assays, all three bacterial strains were monitored for their virulence. Notwithstanding, there is a large number of literature articles that deal with this issue by testing only one bacterial strain (S. epidermidis), usually ATCC 3, 5-7. As we demonstrated in this study, there is a correlation among different degree of hydrophilicity related to different protein adsorption, cholesterol and other molecules absorption, direct effect of vitamin E itself, even if present in very low concentration in the polyethylene, and S. epidermidis adhesion. The obtained results indicate that vitamin E blended UHMWPE reduced the adhesion of all the S. epidermidis strains tested, both the clinical and the laboratory ones, and that the initial adhesion on inert surfaces is strain dependent. As stated in the article, within the limitations of our study, these data must be considered tentative pending results from additional studies to provide a more thorough understanding process through the use of other organisms. Since all microorganisms can colonize an implant system, further studies are ongoing to evaluate the effect of these biomaterials with different chemical surface features also on the adhesion of other pathogens such as S. aureus, MRSA, Pseudomonas aeruginosa, Candida albicans, both clinical and laboratory strains to support a final conclusion of the real clinical value. To transfer into clinical practice experimentally obtained results, an ex vivo failed prosthetic component analysis will be necessary to correlate biomaterials surface with infection.

Adhesion of Staphylococcus epidermidis to Surgical Sutures

Objective: To investigate the interaction of Staphylococcus epidermidis with commonly used surgical sutures and the role of some of this bacterium virulence factors in this interaction. Summary Background Data: Coagulase negative staphylococci are ranked as the second most common cause of postoperative surgical site infections. Sutures have been suggested to act as adhesive surfaces that promote bacterial accumulation. Adherence of S. epidermidis and S. aureus to cardiac sutures has been suggested to be one of the explanations for these organisms being the commonest cause of early prosthetic valve endocarditis. Few S. epidermidis virulence factors have been identified and reported to be involved in this bacterium colonization of biomaterials and biofilm formation. Methods: Different strains of S. epidermidis were incubated with a number of commonly used sutures and examined for their capacity to bind to these sutures. The role of some of S. epidermidis virulence determinants thought to be important in adhesion to foreign bodies and host extracellular matrix proteins were analyzed for their role in the adhesion of this bacterium to sutures. Results: Adherence of S. epidermidis to sutures varied according to the type of material from which the suture was constructed and the strain of bacteria. The major adhesin responsible for binding to sutures was identified as the autolysin (AtlE) of this bacterium. S. epidermidis adhesion significantly increased when suture materials were coated with human plasma. Conclusions: S. epidermidis has a propensity to adhere to surgical sutures and this could increase the risk of wound infection and complications. The results of this study demonstrate that the choice of suture material could seriously impact on the risk of infection and indicate the need for further material development. These studies also suggest that inhibitors of S. epidermidis autolysin (AltE) may be useful coating agents to prevent bacterial adhesion to sutures.

The effects of shear stress on isolated receptor–ligand interactions of Staphylococcus epidermidis and human plasma fibrinogen using molecularly patterned microfluidics

Staphylococcus epidermidis is an opportunistic pathogen that has been implicated in hospital-acquired infections, specifically related to implanted intravascular devices. S. epidermidis adhesion is a mechanism of colonization, leading to pathogenesis. Here we demonstrate an easily fabricated and robust parallel microfluidic platform to investigate the physiologically-relevant effects of fluid shear on S. epidermidis adhesion to human fibrinogen (hFg) with increased experimental throughput. In situ molecular patterning using fluid flow boundaries allows for isolation of the molecular interactions in highly defined shear stress environments, while keeping the device operation simple and reproducible. We characterize two modes of attachment of S. epidermidis to hFg coated surfaces. Single colonies adhere in high fractions at low shear stresses (~1 dyne cm(-2)) and adhesion decays with increasing shear. However, clusters of bacteria adhere the highest at median wall shear stress (up to 10 dyne cm(-2)), and adhesion subsequently decays above this critical shear stress. This initial characterization suggests a previously unobserved phenomenon of shear activated cell-cell adhesion in S. epidermidis, which acts to increase the overall attachment strength to hFg. Both of these modes of attachment are dependant upon the presence of intact hFg, indicating that adhesion is resultant from specific molecular recognition between the bacteria and human fibrinogen. This platform provides new insight into complex host-pathogen interactions, and will allow for further investigation of colonization and pathogenesis in more physiologically relevant conditions.

Differential response of Staphylococci and osteoblasts to varying titanium surface roughness

The surface roughness of metallic orthopaedic implants has typically been used to influence osseointegration and spatially control load transfer to the surrounding bone. Because of the increasing recognition of biomaterials-associated infection as a leading implant failure mode, we are interested to know the relative importance of roughness not only on surface–osteoblast interactions but also on surface–bacteria interactions. This in vitro study thus compares the effects of surface topography on Staphylococcus epidermidis and human osteoblast behavior using four clinically relevant titanium surface finishes: polished, satin, grit-blasted and plasma-sprayed. Important differences between these surfaces are manifested not only by their vertical roughness parameters but also by the lateral length scales over which topographic fluctuations occur. We find that S. epidermidis adhesion and growth is substantially higher on the satin and grit-blasted surfaces than on the polished or plasma-sprayed surfaces. The former are both substantially rougher at length scales comparable to that of bacteria. In contrast, based on imaging and biochemical assays of proliferation, differentiation and matrix formation, we find that desirable osteoblast–surface interactions are maximized on plasma-sprayed surfaces and minimized on satin-finished surfaces. We attribute these differences to the fact that the plasma-sprayed surface is relatively smooth compared to the size of an individual osteoblast, while the satin surface is rough at this length scale. These findings indicate that both the vertical and lateral character of surface roughness can be modified to not only optimize implant–bone interactions but to simultaneously minimize implant–bacteria interactions.

Adherence of Staphylococcus epidermidis to human endothelial cells is associated with a polysaccharidic component of its extracellular mucous layer

Bacterial adherence to eukaryotic cells is highly contributing to microbial pathogenesis. Bacterial adhesins, macromolecules, and glycosaminoglycan chains of the endothelial cell surface have been implicated in staphylococcal attachment. Our research group has isolated an antigenic polysaccharidic component of Staphylococcus epidermidis extracellular layer, known as 20-kDa PS (PS), and showed that antibodies against this polysaccharide protect from infections. Therefore, the role of PS in S. epidermidis adherence to endothelial cells was studied. For this purpose we examined the impact of PS on the ability of two S. epidermidis strains (a PS-producing and a non-PS-producing strain) to adhere to human endothelial cells in the presence or absence of specific antibodies to this polysaccharide. Hence, it is established that exogenous chondroitin sulfate (CS) decreases, in part, the S. epidermidis' attachment to endothelial cells and the antagonistic binding effect of CS and PS was also studied. The results obtained demonstrate that PS facilitates the adherence of S. epidermidis to both strains. CS abolished the PS-induced adherence in PS‐producing strain and partially in the non-PS-producing one. Conclusively, the adherence of S. epidermidis to human endothelial cells is associated with its extracellular PS component and it is suggested that the bacterial binding via glycosaminoglycan chains is an important mechanism underlining the PS-induced binding to endothelial cells.

Biomolecules in multilayer film for antimicrobial and easy-cleaning stainless steel surface applications

Microorganisms are able to attach to, grow on, and ultimately form biofilms on a large variety of surfaces, such as industrial equipment, food contact surfaces, medical implants, prostheses and operating rooms. Once organized into biofilms, bacteria are difficult to remove and kill, which increases the risk of cross-contamination and infection. One way to address the problem may thus be to develop antibacterial, anti-adhesion, ‘easy cleaning’ surfaces. In this study, stainless steel (SS) surfaces with antibacterial properties were created by embedding several antimicrobial peptides in a multilayer film architecture. The biocidal effect of these surfaces was demonstrated against both Gram-positive and Gram-negative bacteria according to two ISO tests. Also, coating SS surfaces with either mucin or heparin led to a reduction of S. epidermidis adhesion of almost 95% vs the bare substratum. Finally, by combining both antibacterial and anti-adhesion biomolecules in the same multilayer film, SS surfaces with better cleanability were produced. This surface coating property may help to delay the buildup of a dead bacterial layer which is known to progressively reduce exposure of the coating, leading to an undesirable decrease in the antibacterial effect of the surface.

Contact Lens Hydrophobicity and Roughness Effects on Bacterial Adhesion

This study was designed to assess whether hydrogel contact lens (CL) surface hydrophobicity and roughness affect Staphylococcus epidermidis adhesion. Bacterial adhesion experiments were performed on two unworn silicone hydrogel and three unworn conventional hydrogel CLs using the S.epidermidis strain CECT 4184. Microbial colonization was assessed by conducting counts expressed as colony-forming units. CL hydrophobicity was determined through water contact angle measurements and the roughness parameters such as mean surface roughness (Ra), kurtosis (Rku), and skewness (Rsk) were determined through atomic force microscopy in Tapping Mode. The conventional CLs showed similar water contact angles (p > 0.05) and were classified as hydrophilic. The silicone hydrogel CLs yielded hydrophobic contact angles with no significant differences between them (p > 0.05). The lenses with the highest (nelfilcon A and ocufilcon B) or lowest (comfilcon A and omafilcon A) Ra values displayed a lesser or greater extent of spikiness of their surfaces, respectively. All lenses showed a predominance of peaks (Rsk > 0) over troughs. S. epidermidis adhered more to the hydrophobic CLs (p < 0.05). Omafilcon A and comfilcon A, which showed the lowest Ra values among the hydrophilic and hydrophobic lenses, respectively, returned the lowest bacterial adhesion scores (p < 0.05). Our results suggest that more hydrophobic CLs are more prone to S. epidermidis adhesion. Although the Ra appears to be related to S. epidermidis adhesion, the influence of Rku and Rsk on this variable remains unclear.