Epidermidis Adhesion Research Articles

Surfactant polymers designed to suppress bacterial (Staphylococcus epidermidis) adhesion on biomaterials.

We describe a series of surfactant polymers designed as surface-modifying agents for the suppression of bacterial adhesion on biomaterials. The surfactant polymers consist of a poly(vinyl amine) backbone with hydrophilic poly(ethylene oxide) (PEO) and hydrophobic hexanal (Hex) side chains (PVAm/PEO:Hex). Surface modification is accomplished by simple dip coating from aqueous solution, from which surfactant polymers undergo spontaneous surface-induced assembly on hydrophobic biomaterials. The stability of PVAm/PEO:Hex on pyrolytic graphite (HOPG) and polyethylene (PE) was demonstrated by the absence of detectable desorption under flow conditions of pure water over a 24-h period. PEO surfactant polymers with four different PEO:Hex ratios (1:1.4, 1:2.5, 1:4.6, and 1:10.7) and a dextran surfactant polymer were compared with respect to S. epidermidis adhesion under dynamic flow conditions. Suppression of S. epidermidis adhesion was achieved for all modified surfaces over the shear range 0-15 dyn/cm(2). The effectiveness depended on the surfactant polymer composition such that S. epidermidis adhesion to modified surfaces decreased significantly with increasing PEO packing density. Modified HOPG was more effective in reducing bacterial adhesion compared with the corresponding modification on PE, which we attribute to the presence of defects in surfactant polymer assembly on PE. Our results are discussed from the perspective of critical factors, such as optimal PEO packing density and hydration thickness, that contribute to the effectiveness of surfactant polymers to shield a biomaterial from adhesive bacterial interactions.

In vitro adherence of staphylococcus epidermidis to polymethyl methacrylate and acrysof intraocular lenses

Purpose To investigate the adherence of one clinically relevant ocular isolate of Staphylococcus epidermidis to polymethyl methacrylate (PMMA) and Acrysof (Alcon Surgical, Fort Worth, TX) intraocular lenses (IOLs). Design Experimental study. Participants The authors examined the in vitro adherence of one clinically relevant ocular isolate of S. epidermidis. Adherence was tested on 12 PMMA IOLs and 12 Acrysof IOLs. Methods Six IOLs (three of each type) were placed in different test tubes containing bacterial suspension (10 8 cfu/ml) and incubated at 37°C. At different times (3 minutes, 30 minutes, and 90 minutes), each IOL type was removed from the test tube, rinsed in sterile phosphate-buffered saline, and transferred into sterile brain-heart infusion broth. The broth with the IOL was sonicated on low power for 3 minutes to remove adhered bacteria. Two serial 10-fold dilutions of the broth containing the dislodged bacteria were plated on mannitol agar plates. The plates were incubated overnight at 37°C and then bacterial colonies were counted. All assays were performed in triplicate. Additional lenses (three of each type) were incubated with S. epidermidis for different times (3 minutes, 30 minutes, and 90 minutes) and then examined with scanning electron microscopy. Main outcome measures The number of adhered bacteria per area (mm 2) of IOL optic was calculated. Statistical analysis included calculation of arithmetic means and 95% confidence intervals ( t test). Results Direct counting of viable adherent bacteria released by sonication showed that the amount of adhered bacteria per area of IOL optic after 3, 30, and 90 minutes’ incubation in S. epidermidis suspension was 0.1 × 10 2/mm 2, 3.6 × 10 2/mm 2, and 11 x 10 2/mm 2 (PMMA IOLs), and 4.4 × 10 2/mm 2, 3.1 × 10 2/mm 2, and 2.3 × 10 2/mm 2 (Acrysof IOLs). Direct counting of adherent bacteria in scanning electron microscopy photographs revealed that the total amount of adhered bacteria per area of IOL optic after 3, 30, and 90 minutes’ incubation in S. epidermidis suspension was 1.1 × 10 2/mm 2, 4.4 × 10 2/mm 2, and 5.5 × 10 2/mm 2 (PMMA IOLs) and 13 × 10 2/mm 2, 33.9 × 10 2/mm 2, and 72 × 10 2/mm 2 (Acrysof IOLs). Conclusions Results suggest that in vitro adherence of S. epidermidis to IOLs is influenced by IOL materials. After 3 minutes’ incubation, Acrysof IOLs appeared to be more permissive to S. epidermidis adherence than PMMA IOLs. The difference was statistically significant ( P < 0.05). However, at 90 minutes, Acrysof IOLs had a lower viable bacterial count than did the PMMA IOLs. Bacterial adherence appeared to be greater in areas with surface irregularities. Adherence of S. epidermidis to IOLs may play a role in the pathogenesis of some forms of endophthalmitis after cataract surgery.

Evaluation of interfacial properties of hyaluronan coated poly(methylmethacrylate) intraocular lenses

Polymethylmethacrylate intraocular lenses (IOLs) were surface-modified by the linking of a overlayer of hyaluronan. In vitro experiments show that the hydrophilic HA overlayer prevents fibroblasts adhesion and greatly reduces Staphyloccous epidermidis adhesion to the IOL surface. To gain insights into the interfacial properties of untreated and hyaluronan-coated PMMA IOLs, force-distance curves were obtained by atomic force microscopy, using standard and modified tips. These measurements allow clear appreciation of the marked difference between the mechanical and chemico-physical properties at the aqueous interface of the uncoated and hyaluronan-coated lenses.

Inhibition by heparin and derivatized dextrans of Staphylococcus epidermidis adhesion to in vitro fibronectin-coated or explanted polymer surfaces

The ability of Staphylococcus to recognize several extracellular matrix or plasma proteins (e.g., fibrinogen, fibronectin, and collagen) promotes bacterial attachment to artificial surfaces. Whereas most S. aureus clinical isolates elaborate a wide repertoire of bacterial surface 'receptors' called adhesins, exhibiting specific binding of individual host proteins, S. epidermidis is lacking most of such protein adhesins. To document the interactions between S. epidermidis and various surface-adsorbed proteins, we first compared promotion of bacterial attachment by seven purified human proteins immobilized onto poly(methyl methacrylate) (PMMA) coverslips. Only two of them, namely fibronectin and fibrinogen, exhibited adhesion-promoting activities. In the presence of native heparin or two functionalized dextrans (CMDBS for Carboxy Methyl, Benzylamide sulfonate/sulfate), a dose-dependent inhibition of S. epidermidis adhesion to fibronectin-coated, but not to fibrinogen-coated surfaces was observed. The inhibitory effects of each CMDBS were much stronger than that of native heparin. In contrast, a control highly negatively charged dextran exclusively substituted with carboxy methyl groups exerted no inhibition on S. epidermidis adhesion. To evaluate how CMDBS could interfere with S. epidermidis attachment to coverslips coated in vivo with extracellular matrix components, we also tested PMMA surfaces retrieved from tissue cages Subcutaneously implanted in guinea pigs. Each CMDBS, but not heparin, strongly inhibited S. epidermidis adhesion to explanted coverslips, even in the presence of tissue cage fluid. In conclusion, fibronectin plays an important role in promoting S. epidermidis attachment to implanted biomaterials. Furthermore, S. epidermidis adhesion to fibronectin-coated or implanted biomaterials can be efficiently blocked in vitro by CMDBS.

Bacterial adhesion on PEG modified polyurethane surfaces

Polyurethane surface was modified with poly(ethylene glycol) (mol. wt. 1000, PEG1k) carrying terminal hydroxyl, amino and sulfonate groups, poly(ethylene glucol) (mol. wt. 3350, PEG3.4k) and PEG3.4k-Heparin, respectively. These surfaces were investigatted for bacterial adhesion using S. epidermidis and E. coli in tryptic soya broth (TSB), brain heart infusion (BHI), and human plasma. All PEG modified surfaces reduced bacterial adhesion significantly and the adhesion level differs depending on surfaces as well as media. In the case of PEG1k surfaces, no reduction of S. epidermidis adhesion was demonstrated in TSB media, regardless of terminal functional groups of PEG1k. However, adhesioin in plasma was reduced to the different degree, depending on terminal groups of PEG1k (least adhesion on sulfonated PEG surface). Relatively longer PEG surface (PEG3.4k) and PEG3.4k-heparin surface minimized bacterial adhesion in both media. In the case of E. coli adhesion, significant reduction in adherent bacteria was observed on all PEG1k, PEG3.4k, and PEG-heparin surfaces in both media compared to controls. In contrast, no reductioin in bacterial adhesion was demonstrated on poly(propylene glycol) (PPG1k) grafted PU surface as compared to control PU. These results suggest that surface modification with PEG1k-SO 3, PEG3.4k and PEG3.4k-heparin seems to be effective for prevention of bacterial adhesion and subsequent infection.

Adhesion of Staphylococcus epidermidis and transposon mutant strains to hydrophobic polyethylene.

Staphylococcus epidermidis capsular polysaccharide adhesin (PS/A) and slime were studied as possible mediators of bacterial adhesion to NHLBI polyethylene (PE) under dynamic flow. This putative interaction was examined by quantifying the adhesion of M187 (PS/A+, slime+) parent strain and isogenic transposon mutant strain sn3 (PS/A-, slime-) to polyethylene (PE) under a range of physiologic shear stress conditions in both phosphate-buffered saline (PBS) and 1% platelet poor plasma (PPP). No significant differences in adhesion were noted between the M187 and sn3 strains in either test medium. However, adhesion of both strains in 1% PPP was decreased 75-95% compared to adhesion in PBS. In PBS, adhesion was shear stress dependent from 0-15 dyne/cm2, after which adhesion was comparatively shear stress independent. Adhesion in 1% PPP was independent of shear stress. Epifluorescent imaging of both strains labeled for slime confirmed the presence of slime on the surface of M187 and suggested that PS/A and slime promote the formation of large aggregates, as aggregates were totally absent in the images of the sn3 strain. The results suggest that PS/A and slime do not mediate S. epidermidis adhesion to bare PE or PE with adsorbed plasma proteins, but may be necessary for intercellular adhesion, which is important for biofilm formation.

Surface characteristics and biocompatibility of lactide-based poly(ethylene glycol) scaffolds for tissue engineering

Novel lactide-based poly(ethylene glycol) (PEG) polymer networks (GL9-PEGs) were prepared by UV copolymerization of a glycerol-lactide triacrylate (GL9-Ac) with PEG monoacrylate (PEG-Ac) to use as scaffolds in tissue engineering, and the surface properties and biocompatibility of these networks were investigated as a function of PEG molecular weight and content. Analysis by ATR-FTIR and ESCA reveled that PEG was incorporated well within the GL9-PEG polymer networks and was enriched at the surfaces. From the results of SEM, AFM, and contact angle analyses, GL9-PEG networks showed relatively rough and irregular surfaces compared to GL9 network, but the mobile PEG chains coupled at their termini were readily exposed toward the aqueous environment when contacting water such that the surfaces became smoother and more hydrophilic. This reorientation and increase in hydrophilicity were more extensive with increasing PEG molecular weight and content. As compared to GL9 network lacking PEG, protein adsorption as well as platelet and S. epidermidis adhesion to GL9-PEG networks were significantly reduced as the molecular weight and content of PEG was increased, indicating that GL9-PEG networks are more biocompatible than the GL9 network due to PEG's passivity. Based on the physical and biological characterization reported, the GL9-PEG materials would appear to be interesting candidates as matrices for tissue engineering.

Influence of strain, biomaterial, proteins, and oncostatic chemotherapy on staphylococcus epidermidis adhesion to intravascular catheters in vitro

Initial adhesion of four phenotypically different strains of Staphylococcus epidermidis to 16 silicone, polyurethane, or hydrophilic polyurethane catheters was assessed in vitro by a bacterial radiolabeling method. The effect of catheter exposure to plasma proteins, to an anticancer polychemotherapy (5-fluorouracil, doxorubicin, cyclophosphamide), or to both of them was determined. Bacterial adhesion on native catheters was dependent on the hydrophobicity of both bacteria and catheters. The four strains tested adhered preferentially to silicone catheters ( p < 0.05); adhesion was moderate to polyurethane surfaces, whereas the least adhesion was obtained for hydrophilic polyurethane catheters. Adsorption of plasma proteins on the surface produced a marked decrease in adhesion on silicone (−66.2%; p < 0.001) and polyurethane (−32.8%; p < 0.01) catheters and a marked increase in adhesion on hydrophilic surfaces (+91.7%; p < 0.05). Chemotherapeutic treatment of the catheter produced a slight but not significant decrease in adhesion on silicone (−17.4%) and polyurethane (−19.8%) catheters and a marked increase in adhesion on hydrophilic polyurethanes (+148.2%; p < 0.001). The in vitro simulation of catheter use suggested that oncostatic drugs and plasma proteins play an important role in S. epidermidis adhesion to intravascular catheters. Overall, bacterial adhesion is lowest on hydrophilic polyurethane catheters before and after simulation of catheter use.

Rapid quantification of staphylococci adhered to titanium surfaces using image analyzed epifluorescence microscopy

A method for rapid enumeration of S. epidermidis adhered to the surface of commercially pure titanium samples was developed using image analyzed epifluorescence microscopy. The method was used to determine the effects of different surface roughnesses of titanium samples and the influence of adsorbed human serum proteins on bacterial adherence. Bacterial suspension of S. epidermidis (VAS-11, concentration: 10 7 cfu/ml) were incubated with titanium samples (with different surface roughnesses and coated with human serum albumin or fibronectin) for 1 h at 37°C with agitation. Thereafter they were washed, stained with propidium iodide, air dried, mounted onto microslides, and counted by using image analyzed epifluorescence microscopy. The results showed that: (1) this direct counting method is quick, simple, accurate, reproducible, and suitable for counting bacteria adhered to opaque surfaces such as netal, (2) the different roughnesses of the titanium surfaces (roughness: 1.25 to 0.44 Ra) had no effect on the S. epidermidis adherence, and (3) adsorbed human serum albumin reduced the S. epidermidis adherence by more than 90%, suggesting that precoating biomaterials with albumin may reduce the possibility of prosthesis or implant colonization by staphylococci. Conversely, human serum fibronection had no effect on S. epidermidis adherence to a titanium surface.

Adhesion of Staphylococcus epidermidis to biomedical polymers: Contributions of surface thermodynamics and hemodynamic shear conditions

Adhesion studies of Staphylococcus epidermidis RP62A were conducted using a rotating disk system to determine the roles of surface physicochemistry and topographies under physiologic shear conditions. Six materials were investigated: biomedical reference polyethylene and polydimethylsiloxane; argon plasma-treated reference polyethylene (Ar-PE); Silastic; expanded polytetrafluoroethylene; and woven Dacron. All of the polymers except Dacron demonstrated reduced bacterial adhesion with increasing shear stress. Argon plasma treatment of polyethylene reduced the level of staphylococcal adhesion. Adsorption of human plasma proteins effected significantly lower numbers of adherent bacteria. The lowest adhesion was observed for Ar-PE in 1% human plasma protein solution, whereas Dacron had the highest number of adherent bacteria. The high adhesion on Dacron was attributed to increased bacterial flux caused by topography-induced turbulent flow and physical entrapment of the bacteria in the fiber interstices. The results indicate that the driving force for S. epidermidis adhesion is strongly influenced by substrate physicochemistry, but this may be dominated by physical forces such as shear and turbulence.

Platelet-mediated adhesion of Staphylococcus epidermidis to hydrophobic NHLBI reference polyethylene.

The effects of platelets and plasma proteins on the adhesion of Staphylococcus epidermidis strain RP62A to hydrophobic NHLBI reference polyethylene was quantitatively studied using a rotating disk system to generate well-defined shear conditions simulating the hemodynamics of human blood circulation. Bacterial adhesion was quantified by adhesive coefficient, the percentage of bacteria transported to the surface that becomes adherent. The results showed that surface modification by adsorption of plasma proteins reduced the adhesion of S epidermidis as compared to the bare polymer surface. This surface modification was not sufficient to eliminate completely bacterial adhesion, even at the highest physiologic shear stress level. S epidermidis did adhere strongly to polyethylene surface modified by platelets. This is readily evident as approximately 50% of the adherent S epidermidis were bound to contact-activated platelets which occupied only 4% of the surface area. Adhesive coefficients to platelets were significantly greater than to the protein-adsorbed polyethylene surface by at least one order of magnitude (P < or = .01) across the range of physiological shear conditions investigated. These studies show that it is biologic surface modification by contact-activated platelets, and not plasma proteins, which mediates S epidermidis adhesion to polyethylene.

Staphylococcus epidermidis adhesion to hydrophobic biomedical polymer is mediated by platelets.

A quantitative investigation on the effects of plasma proteins and platelets on the adhesion of Staphylococcus epidermidis RP62A to a hydrophobic biomedical polymer (National Heart, Lung, and Blood Institute reference polyethylene) was carried out under well-defined shear conditions approximating human blood circulation by using a rotating disk system. The results showed that contact-activated platelets mediated S. epidermidis adhesion to the polymer surface. In the range of physiologic shear conditions, the adhesive coefficient (ratio of bacteria per unit area to the product of bacterial flux and the duration of the experiment) to platelets was significantly greater than to the protein-adsorbed polyethylene surface by at least one order of magnitude (P < or = .01). The presence of absorbed plasma proteins on polyethylene reduced the adhesion of S. epidermidis compared with that seen with the bare polymer surface. These studies show that S. epidermidis adhesion to polyethylene is mediated by contact-activated platelets, not absorbed plasma proteins.

The effect ofStaphylococcus epidermidis adherence to biomaterials—On antibiotic susceptibility, antibiotic release, and infection risk

The effect ofStaphylococcus epidermidis adherence to biomaterials—On antibiotic susceptibility, antibiotic release, and infection risk

Scanning Electron Microscopy of Staphylococcus Epidermidis Adherence to Continuous Ambulatory Peritoneal Dialysis Catheters

Infections associated with the use of intravascular devices have been documented and have been reported to be related to duration of catheter usage. Recently, Eaton et al. reported that Staphylococcus epidermidis may attach to silastic catheters used in continuous ambulatory peritoneal dialysis (CAPD) treatment. The following study presents findings using scanning electron microscopy (SEM) of S. epidermidis adherence to silastic catheters in an in vitro model. In addition, sections of polyvinyl chloride (PVC) dialysis bags were also evaluated by SEM.The S. epidermidis strain RP62A which had been obtained in a previous outbreak of coagulase-negative staphylococcal sepsis at local hospitals was used in these experiments. The strain produced surface slime on exposure to glucose, whereas a nonadherent variant RP62A-NA, which was also used in these studies, failed to produce slime. Strains were grown overnight on blood agar plates at 37°C, harvested from the surface and resuspended in sterile saline (0.85%), centrifuged (3,000 rpm for 10 minutes) and then washed twice in 0.1 M phosphate-buffered saline at pH 7.0. Organisms were resuspended at a concentration of ca. 106 CFU/ml in: a) sterile unused dianeal at 4.25% dextrose, b) sterile unused dianeal at 1.5% dextrose, c) sterile used dialysate previously containing 4.25% dextrose taken from a CAPD patient, and d) sterile used dialysate previously containing 1.5% dextrose taken from a CAPD patient.