Phagocytosis and macrophage polarization on bacterially contaminated dental implant materials and effects on tissue integration.

Bacterial contamination is hard to avoid during dental implant surgery. Macrophages and their polarisation play a decisive role in bacterial colonisation and tissue integration on bacterially contaminated dental implants. The present study investigated the role of macrophages in stimulating tissue coverage overgrowth of contaminating oral bacteria on polished titanium (Ti-P) and acid-etched zirconium dioxide (ZrO2-MA) dental implant materials. Different co-culture models were employed to determine phagocytosis rates of Streptococcus mitis or Staphylococcus aureus contaminating a dental implant surface and the influence of contaminating bacteria and osteoblasts (U2OS) on macrophage polarisation. S. aureus was phagocytized in higher numbers than S. mitis in bi-cultures on smooth Ti-P surfaces. Contaminating S. mitis stimulated near full polarisation of macrophages from a non-Ym1-expressing- to a Ym1-expressing-phenotype on smooth Ti-P, but on ZrO2-MA both phenotypes occurred. In tri-cultures with U2OS-cells on smooth Ti-P, a larger percentage of macrophages remained in their non-Ym1-expressing, "fighting" M1-like phenotype to clear Ti-P surfaces from contaminating bacteria. On ZrO2-MA surfaces, more macrophages tended towards their "fix- and-repair" M2-like phenotype than on Ti-P surfaces. Surface coverage of smooth, bacterially contaminated Ti-P surfaces by U2OS-cells was more effectively stimulated by fighting, M1-like macrophages than on ZrO2-MA surfaces. Comprehensive guidelines are provided for the development of infection-resistant, dental implant materials, including bacteria, tissue and immune cells. These guidelines point to more promising results for clinical application of Ti-P as compared with ZrO2-MA.

Influence of surface roughness on silicone rubber voice prostheses on in vitro biofilm formation and clinical lifetime in laryngectomised patients.

OBJECTIVES: Evaluation of the influence of a smooth surface moulding technique of silicone rubber indwelling voice prostheses on in vitro biofilm formation and analysis of the clinical in situ lifetime. DESIGN: Biofilm formation on smooth and Groningen ultra low resistance (URL) prostheses was studied in an artificial throat model. The clinical lifetime of smooth voice prostheses was compared to the previous lifetime of URL by counting the number of replacements in a consecutive 6-month period in the same patient. PARTICIPANTS: Eleven laryngectomised patients in follow-up who required frequent replacement of their voice prostheses. SETTINGS: Tertiary University Medical Center. RESULTS: Use of a smoother mould and less viscous silicone rubber yielded a decrease in surface roughness from 46 to 8 nm and was accompanied by a 40% reduction in the prevalence of bacteria and yeast in in vitro formed biofilms. Clinically, the lifetime was significantly (P<.005) increased by a factor of 2.1. CONCLUSIONS: This combined in vitro and clinical study suggests that the choice of material and in particular its surface finishing may be determining factors with respect to the clinical lifetime of silicone rubber implants and devices failing due to biofilm formation.

A biodegradable gentamicin-hydroxyapatite-coating for infection prophylaxis in cementless hip prostheses.

A degradable, poly (lactic-co-glycolic acid) (PLGA), gentamicin-loaded prophylactic coating for hydroxyapatite (HA)-coated cementless hip prostheses is developed with similar antibacterial efficacy as offered by gentamicin-loaded cements for fixing traditional, cemented prostheses in bone. We describe the development pathway, from in vitro investigation of antibiotic release and antibacterial properties of this PLGA-gentamicin-HA-coating in different in vitro models to an evaluation of its efficacy in preventing implant-related infection in rabbits. Bone in-growth in the absence and presence of the coating was investigated in a canine model. The PLGA-gentamicin-HA-coating showed high-burst release, with antibacterial efficacy in agar-assays completely disappearing after 4 days, minimising risk of inducing antibiotic resistance. Gentamicin-sensitive and gentamicin-resistant staphylococci were killed by the antibiotic-loaded coating, in a simulated prosthesis-related interfacial gap. PLGA-gentamicin-HA-coatings prevented growth of bioluminescent staphylococci around a miniature-stem mounted in bacterially contaminated agar, as observed using bio-optical imaging. PLGA-gentamicin-HA-coated pins inserted in bacterially contaminated medullary canals in rabbits caused a statistically significant reduction in infection rates compared to HA-coated pins without gentamicin. Bone ingrowth to PLGA-gentamicin-HA-coated pins, in condylar defects of Beagle dogs was not impaired by the presence of the degradable, gentamicin-loaded coating. In conclusion, the PLGA-gentamicin-HA-coating constitutes an effective strategy for infection prophylaxis in cementless prostheses.

The implant infection paradox: why do some succeed when others fail? Opinion and discussion paper.

Biomaterial-implants are frequently used to restore function and form of human anatomy. However, the presence of implanted biomaterials dramatically elevates infection risk. Paradoxically, dental-implants placed in a bacteria-laden milieu experience moderate failure-rates, due to infection (0.0-1.1%), similar to the ones of joint-arthroplasties placed in a near-sterile environment (0.1-1.3%). Transcutaneous bone-fixation pins breach the immune-barrier of the epidermis, exposing underlying sterile-tissue to an unsterile external environment. In contrast to dental-implants, also placed in a highly unsterile environment, these pins give rise to relatively high infection-associated failure-rates of up to 23.0%. Herein, we attempt to identify causes as to why dental-implants so often succeed, where others fail. The major part of all implants considered are metal-made, with similar surface-finishes. Material choice was therefore discarded as underlying the paradox. Antimicrobial activity of saliva has also been suggested as a cause for the success of dental-implants, but was discarded because saliva is the implant-site-fluid from which viable bacteria adhere. Crevicular fluid was discarded as it is largely analogous to serum. Instead, we attribute the relative success of dental-implants to (1) ability of oral tissues to heal rapidly in the continuous presence of commensal bacteria and opportunistic pathogens, and (2) tolerance of the oral immune-system. Inability of local tissue to adhere, spread and grow in presence of bacteria and an intolerant immune-system are identified as the likely main causes explaining the susceptibility of other implants to infection-associated failure. In conclusion, it is the authors' belief that new anti-infection strategies for a wide range of biomaterial-implants may be derived from the relative success of dental-implants.

Antimicrobial penetration in a dual-species oral biofilm after noncontact brushing: an in vitro study.

OBJECTIVES: Oral biofilm is inevitably left behind, even after powered brushing. As a special feature, powered brushing removes biofilm in a noncontact mode. When the brushing distance becomes too large, biofilm is left behind. We hypothesize that biofilm left behind after brushing has different viscoelastic properties than before brushing, impacting antimicrobial penetration. MATERIALS AND METHODS: In vitro grown dual-species biofilms were subjected to 20 % mechanical deformation before and after powered brushing at 4-mm brushing distance. Biofilm thickness and stress relaxation were measured for unbrushed and brushed biofilms. Stress relaxation was analyzed with a three-element Maxwell model. Antimicrobial penetration from five mouthrinses was microscopically evaluated for unbrushed and brushed biofilms. RESULTS: Thicknesses of unbrushed and brushed biofilms were similar. Brushing decreased the prevalence of fast and increased the prevalence of slow relaxation elements, which was accompanied by deeper penetration of chlorhexidine and cetylpyridinium chloride. Penetration of antimicrobials from other mouthrinses was relatively low in unbrushed and brushed biofilms. CONCLUSIONS: This confirmation of our hypothesis points to an additional advantage of powered toothbrushing in a noncontact mode, changing the viscoelastic properties of biofilm in a direction that increases antimicrobial penetration of chlorhexidine and cetylpyridinium. CLINICAL RELEVANCE: The biofilm left behind after noncontact powered toothbrushing may have less recalcitrance toward penetration of chlorhexidine and cetylpyridinium chloride than prior to brushing.

Bacterial biofilm formation versus mammalian cell growth on titanium-based mono- and bi-functional coating.

Biomaterials-associated-infections (BAI) are serious complications in modern medicine. Although non-adhesive coatings, like polymer-brush coatings, have been shown to prevent bacterial adhesion, they do not support cell growth. Bi-functional coatings are supposed to prevent biofilm formation while supporting tissue integration. Here, bacterial and cellular responses to poly(ethylene glycol) (PEG) brush-coatings on titanium oxide presenting the integrin-active peptide RGD (arginine-glycine-aspartic acid) (bioactive "PEG-RGD") were compared to mono-functional PEG brush-coatings (biopassive "PEG") and bare titanium oxide (TiO2) surfaces under flow. Staphylococcus epidermidis ATCC 35983 was deposited on the surfaces under a shear rate of 11 s-1 for 2 h followed by seeding of U2OS osteoblasts. Subsequently, both S. epidermidis and U2OS cells were grown simultaneously on the surfaces for 48 h under low shear (0.14 s-1). After 2 h, staphylococcal adhesion was reduced to 3.6-/+1.8 x 103 and 6.0-/+3.9 x 103 cm-2 on PEG and PEG-RGD coatings respectively, compared to 1.3-/+0.4 x 105 cm-2 for the TiO2 surface. When allowed to grow for 48 h, biofilms formed on all surfaces. However, biofilms detached from the PEG and PEG-RGD coatings when exposed to an elevated shear (5.6 s-1) U2OS cells neither adhered nor spread on PEG brush-coatings, regardless of the presence of biofilm. In contrast, in the presence of biofilm, U2OS cells adhered and spread on PEG-RGD coatings with a significantly higher surface coverage than on bare TiO2. The detachment of biofilm and the high cell surface coverage revealed the potential significance of PEG-RGD coatings in the context of the "race for the surface" between bacteria and mammalian cells.

Energy transfer, volumetric expansion, and removal of oral biofilms by non-contact brushing.

Non-contact removal of oral biofilms offers advantages beyond the reach of bristles, but it is unknown how energy transfer for removal from brush-to-biofilm occurs. In the present study we evaluated non-contact, oral biofilm removal by oscillating-rotating and sonic toothbrushes, and their acoustic output up to 6 mm distance. Whereas some brushes removed biofilm when used at a distance of up to 6 mm, others lost efficacy at a distance of 2-4 mm from the biofilm. Loss of efficacy was accompanied with high standard deviations and volumetric biofilm expansion. Both sonic and oscillating-rotating brushes caused fluid flows and the inclusion of air-bubbles, while non-contact acoustic energy-transfer was demonstrated to decay with distance for both types of brushes. We put forward the following mechanism for non-contact removal: (i) brush energy is absorbed by biofilm, resulting in the visco-elastic expansion of the biofilm; (ii) if the energy absorbed is sufficient and deformation is beyond the yield point, biofilm removal occurs; and (iii) if deformation is in the plastic range but below the yield point (i.e. at the limiting distance for non-contact removal), biofilm is expanded but not removed.

Retention of antimicrobial activity in plaque and saliva following mouthrinse use in vivo.

The aim of this study was to determine the contribution of plaque and saliva towards the prolonged activity, also called substantivity, of three antimicrobial mouthrinses (Listerine®, Meridol®, Crest Pro Health®), used in combination with a toothpaste (Prodent Coolmint®). Volunteers brushed for 4 weeks with a toothpaste without antimicrobial claims, while during the last 2 weeks half of the volunteers used an antimicrobial mouthrinse in addition to brushing. At the end of the experimental period, plaque and saliva samples were collected 6 h after oral hygiene, and bacterial concentrations and viabilities were determined. The contribution of plaque and saliva towards substantivity was assessed by combining plaque obtained after mechanical cleaning only with plaque and saliva obtained after additional use of an antimicrobial rinse. Subsequently, resulting viabilities of the combined plaques were determined. The viabilities of plaque samples after additional rinsing with mouthrinses were lower than of plaque obtained after mechanical cleaning only, regardless of the rinse involved. Moreover, plaque collected 6 h after rinsing with antimicrobial mouthrinses contained a surplus of antimicrobial activity. Only Listerine showed decreased viability in saliva, but none of the mouthrinses showed any residual antimicrobial activity in saliva. The findings indicate that plaque left behind after mechanical cleaning contributes to the prolonged substantivity of antimicrobial mouthrinses.

Microbubble-enriched lavage fluid for treatment of experimental peritonitis.

BACKGROUND: Relaparotomies and closed postoperative peritoneal lavage (CPPL) are performed to treat persistent peritonitis. This experimental animal study compared open abdominal lavage with CPPL, and evaluated the potential of microbubble-enriched lavage fluids to improve the efficiency of CPPL and reduce clinical morbidity, mortality and cost. METHODS: Fluorescent polystyrene spheres were injected intraperitoneally into 22 male Wistar rats to simulate localized peritonitis. After 18 h the rats received open abdominal lavage and CPPL, with and without microbubbles. Microbubbles were obtained by adding ultrasound contrast agents to continuous ambulatory peritoneal dialysis fluid. RESULTS: Open abdominal lavage was 3.5 times more effective in particle removal than CPPL, owing to better fluid dynamics. The introduction of air-liquid interfaces in the form of microbubbles made CPPL up to 2.4 times more effective than lavage without bubbles. Best detachment results were obtained when microbubbles with a flexible surfactant shell and longer blood elimination half-life were used. CONCLUSION: Open abdominal and CPPL lavage techniques are not efficient beyond a certain duration and volume as they do not cause bacterial detachment from the peritoneal membrane. Using surface tension forces from microbubbles significantly enhanced polystyrene particle detachment. These findings may have great consequences for the treatment of patients with peritonitis.

Effects of amine fluoride on biofilm growth and salivary pellicles.

The amine fluoride (AmF) N'-octadecyl-trimethylene-diamine-N,N,N'-tris(2-ethanol)-dihydro-fluoride is a cationic antimicrobial which can have beneficial effects on plaque formation. Here, we determine changes in pellicle and bacterial cell surface properties of the strains Actinomyces naeslundii HM1, Streptococcus mutans NS, S.mutans ATCC 700610, S. sobrinus HG1025 and S. oralis HM1 upon adsorption of this AmF and accompanying effects on bacterial adhesion and biofilm growth. In vitro pellicles had a zeta potential of -12 mV that became less negative upon adsorption of AmF. The chemical functionalities in which carbon and oxygen were involved changed after AmF adsorption and AmF-treated pellicles had a greater surface roughness than untreated pellicles. Water contact angles in vitro decreased from 56 to 45 degrees upon AmF treatment, which corresponded with water contact angles (44 degrees ) measured intraorally on the front incisors of volunteers immediately after using an AmF-containing toothpaste. All bacterial strains were negatively charged and their isoelectric points (IEP) increased upon AmF adsorption. Minimal inhibitory concentrations were smallest for strains exhibiting the largest increase in IEP. Adhesion to salivary pellicles and biofilm growth of the mutans streptococcal strains were significantly reduced after AmF treatment, but not of A. naeslundii or S. oralis. However, regardless of the strain involved, biofilm viability decreased significantly after AmF treatment. The electrostatic interaction between cationic AmF and negatively charged bacterial cell surfaces is pivotal in establishing reduced biofilm formation by AmF through a combination of effects on initial adhesion and killing. The major effect of AmF treatment, however, was a reduction brought about in biofilm viability.

Surface properties of Indonesian-made narrow dynamic compression plates.

The enormous need of orthopaedic (surgical) implants such as osteosynthesis plates is difficult to be fulfilled in developing countries commonly rely on imported ones. One of the alternatives is utilization of local resources, but only after they have been proven safe to use, to overcome this problem. Surface properties are some of the determining factors of safety for those implants. We have succeeded in developing prototype of osteosynthesis plate and the results indicate that Indonesian-made plates need improvement with regards to the surface quality of physical characterization.

Sequence of oral bacterial co-adhesion and non-contact brushing.

Non-contact plaque removal offers advantages in interproximal spaces, fissures, and pockets. It requires the generation of strong fluid flows and the inclusion of air bubbles to become effective. A pair of co-adhering streptococci and actinomyces has been used previously to demonstrate non-contact removal by sonic brushing. Here we determined the influence of the sequence of co-adhesion of streptococci and actinomyces on non-contact removal from a salivary pellicle by rotary and sonic brushing. After bacterial adhesion, pellicles were brushed in a wet and immersed state, with a distance up to 4 mm to the bristle tips. Bacteria adhering to pellicles from the sequence streptococci followed by actinomyces appeared more difficult to remove and left more large co-aggregates than from the sequence actinomyces followed by streptococci. At contact, rotary and sonic brushing performed equally well in bacterial removal, while at 4 mm, both had lost some efficacy.

Influence of biosurfactant on interactive forces between mutans Streptococci and enamel measured by atomic force microscopy.

Although interactive forces, influenced by environmental conditions, between oral bacteria and tooth surfaces are important for the development of plaque, they have never been estimated. It is hypothesized that interactive forces, as measured by atomic force microscopy, between enamel with or without a pellicle and two strains of mutans streptococci become less attractive by the application of a Streptococcus mitis BMS biosurfactant coating. Upon approach of each of the strains toward bare and pellicle-coated enamel, adsorbed biosurfactant increased the range of the repulsive forces. Upon retraction of the enamel surface, small adhesion forces (0.8-0.9 nN) were measured for bare enamel that almost disappeared after biosurfactant coating. The prevalence and magnitude of the adhesion forces also decreased upon pellicle-coating of the enamel, with a minor effect of adsorbed biosurfactant. These findings indicate that adsorbed S. mitis BMS biosurfactant changes the interactive forces between the mutans streptococci studied and enamel, explaining the effects of biosurfactant on adhesion.

Antimicrobials Influence Bond Stiffness and Detachment of Oral Bacteria.

Oral biofilm can never be fully removed by oral hygiene measures. Biofilm left behind after brushing is often left behind on the same sites and exposed multiple times to antimicrobials from toothpastes and mouthrinses, after which removal becomes increasingly difficult. On the basis of this observation, we hypothesize that oral bacteria adhering to salivary conditioning films become more difficult to remove after adsorption of antimicrobials due to stiffening of their adhesive bond. To verify this hypothesis, bacteria adhering to bare and saliva-coated glass were exposed to 3 different mouthrinses, containing chlorhexidine-digluconate, cetylpyridinium-chloride, or amine-fluoride, after which bacterial vibration spectroscopy was carried out or a liquid-air interface was passed over the adhering bacteria to stimulate their detachment. Brownian motion-induced nanoscopic vibration amplitudes of 4 oral streptococcal strains, reflecting their bond stiffness, decreased after exposure to mouthrinses. Concurrently, the percentage detachment of adhering bacteria upon the passage of a liquid-air interface decreased after exposure to mouthrinses. A buffer control left both vibration amplitudes and detachment percentages unaffected. Exposure to either of the selected mouthrinses yielded more positively charged bacteria by particulate microelectrophoresis, suggesting antimicrobial adsorption to bacterial cell surface components. To rule out that exposure of adhering bacteria to the mouthrinses stimulated polysaccharide production with an impact on their detachment, Fourier transform infrared spectroscopy was carried out on bacteria adhering to an internal reflection element, prior to and after exposure to the mouthrinses. Infrared absorption band areas indicated no significant change in amount of polysaccharides after exposure of adhering bacteria to mouthrinses, but wave number shifts demonstrated stiffening of polysaccharides in the bond, as a result of antimicrobial adsorption to the bacterial cell surface and in line with changes in surface charge. Clinically, these findings suggest that accumulation of oral biofilm exposed to antimicrobials should be prevented (interdental cleaning aids, floss use), as removal becomes progressively more difficult upon multiple exposures.

Electric block current induced detachment from surgical stainless steel and decreased viability of Staphylococcus epidermidis.

In vitro studies investigating the influence of electric DC current on bacterial detachment have demonstrated that continuous currents of only 25-125 microA stimulated staphylococcal strains to detach from surgical stainless steel. However, DC currents produce more power that has to be dissipated by the skin as compared to alternating currents. Also, an excess of ions on the steel can cause negative osteogenesis and fixation results. Therefore, it is the aim of this paper to examine whether detachment of Staphylococcus epidermidis from stainless steel surfaces in a parallel plate flow chamber can also be stimulated using electric block currents. Block currents of 15, 60 and 100 microA with different frequencies (0.1-2 Hz) and duty cycles (5-50%) were applied to induce bacterial detachment. Block currents of 100 microA cause detachment of about 76% of adhering staphylococci from stainless steel, whereas in addition the remaining bacteria are less viable, as determined by culturing the remaining bacteria on agar plates. Therewith, block current-induced detachment of adhering bacteria from stainless steel appears to be an equally promising method to prevent infection of orthopaedic fixation pins and screws than application of DC currents.

Bacterial survival in the interfacial gap in gentamicin-loaded acrylic bone cements.

Clinical experience indicates the beneficial effects of antibiotic-loaded bone cement. Although in vitro studies have shown the formation of a biofilm on its surface they have not considered the gap between the cement and the bone. We have investigated bacterial survival in that gap. Samples with gaps 200 microm wide were made of different bone cements. These were stored dry ('pre-elution') or submersed in phosphate-buffered saline to simulate the initial release of gentamicin ('post-elution'). The gaps were subsequently inoculated with bacteria, which had been isolated from infected orthopaedic prostheses and assessed for their sensitivity to gentamicin. Bacterial survival was measured 24 hours after inoculation. All the strains survived in plain cements. In the pre-elution gentamicin-loaded cements only the most gentamicin-resistant strain, CN5115, survived, but in post-elution samples more strains did so, depending on the cement tested. Although high concentrations of gentamicin were demonstrated in the gaps only the gentamicin-sensitive strains were killed. This could explain the increased prevalence of gentamicin-resistant infections which are seen clinically.

Bacterial adhesion to surface hydrophilic and hydrophobic contact lenses.

The aim of this paper was to determine the adhesion of two physico-chemically characterized bacterial strains to a surface hydrophilic (CL A, water contact angle 57 degrees) and hydrophobic (CL B, water contact angle 106 degrees) hydrogel contact lens (CL) with and without an adsorbed tear film in a parallel plate flow chamber. Hydrophobicity (by water contact angles), charge (by particulate microelectrophoresis) and elemental composition (by XPS) of the surfaces of seven bacterial strains were characterized, after which two strains were selected for further studies. On CL surfaces, hydrophobicity, elemental composition, and mean surface roughness (by AFM) were determined, as well as the protein composition of tear films adsorbed on these lenses (by sodium dodecylsulphate-polyacrylamide gel electrophoresis (SDS-PAGE)). Bacterial cell surfaces were relatively uncharged and water contact angles on lawns of different strains ranged from hydrophobic to hydrophilic. After adsorption of tear film components, N/C elemental surface concentrations increased on CL A and CL B and differences in water contact angles between both lenses reduced to range from 57 degrees (CL A) to 69 degrees (CL B). However, different protein compositions were inferred. The surface roughness of CL A increased from 4 to 13 nm. while it remained 16 nm for CL B. Adhesion of hydrophobic Pseudomonas aeruginosa #3 was more extensive than of hydrophilic Staphylococcus aureus 799, with no differences between both lenses. The hydrophobicity of P. aeruginosa #3 after cell surface damage decreased and its adhesion was reduced on CL A and strongly on CL B. In addition, passage of an air-liquid interface yielded more detachment of S. aureus 799 than of P. aeruginosa #3 from the CL surfaces. In conclusion, the hydrophobicity of CL surfaces dictates the composition of the adsorbed tear film and therewith plays an important role in bacterial adhesion to lenses. Adhesion of hydrophobic P. aeruginosa #3 was more tenacious than of hydrophilic S. aureus 799.

In vivo quantification of cell-polymer interactions.

An in vivo rat model was developed to determine cell-polymer interactions under physiological conditions. Microporous tubular grafts, made of polytetrafluoroethylene, a polyetherurethane, a polyesterurethane and also a modified polyetherurethane were implanted intraperitoneally in rats. The grafts were filled with cultured rat smooth muscle cells prior to implantation. At t = 0, 2 and 48 h, the grafts were evaluated macroscopically and also prepared for light microscopy and for cell count of their contents. At t = 0 no cellular attachment was observed on the lumenal side of the capsules. At t = 2 h a monolayer of smooth muscle cells could be observed on all materials except PTFE, on which only small patches of cells were observed. At t = 48 h a multilayer of cells was seen on all materials except PTFE. Cell counts at 48 h demonstrated no multiplication in the PTFE graft but a 1.4, 2.3 and 2.0-fold multiplication in the polyetherurethane, polyesterurethane and the modified polyurethane grafts respectively. These in vivo results show a clear linear relationship with our in vitro results in which it has been proved that cell spreading increased with increasing substratum surface free energy. This rat model allows the study of cell-polymer interactions in vivo, in a standardized way, under controlled physiological conditions.

Backgrounds of antibiotic-loaded bone cement and prosthesis-related infection.

Antibiotic-loaded bone cement has been in use for over 30 years for the fixation of total joint arthroplasties, although its mechanism of action is still poorly understood. This review presents the backgrounds of bone cements, prosthesis-related infection and antibiotic-loaded bone cements. It is shown that antibiotic-loaded bone cement has a significant effect on bacteria, particularly in animal and clinical studies. However, recently, antimicrobial resistance among bacteria has been ascribed to the antibiotic-loaded bone cement. The unresolved issues both regarding the action of antibiotic-loaded bone cement and the nature of the antimicrobial resistance necessitate further research into the interaction of antibiotic-loaded bone cement and bacteria.

Adhesion of Lactobacillus species in urine and phosphate buffer to silicone rubber and glass under flow.

Coating uroepithelial cells or catheter materials with lactobacilli has been shown to retard the development of a uropathogenic biofilm, with biosurfactant production and strong adhesion being two prerequisite properties of the Lactobacillus strains to be employed. In this paper, adhesion of six selected Lactobacillus strains to silicone rubber and glass in urine and in a phosphate buffer was studied using a parallel plate flow chamber. In addition, adhesive cell surface properties of the lactobacilli, i.e. the pH dependences of their zeta potentials and their hydrophobicities by water contact angles, were determined. L. acidophilus ATCC 4356 and L. fermentum B54 were the only strains showing significant adhesion to both hydrophobic silicone rubber and hydrophilic glass, possibly by virtue of their high cell surface hydrophobicities (water contact angles of 68 and 75 degrees, respectively) and small zeta potentials (-10.0 and -8.1 mV in buffer, respectively). Both hydrophobic Lactobacillus strains adhered less well in urine than in buffer. The remaining Lactobacillus strains studied were hydrophilic, with water contact angles between 25 and 36 degrees, and had highly negative zeta potentials, reaching -37.7 mV in buffer. Adhesion of these highly negatively charged, hydrophilic strains in buffer was essentially absent, while for some of these strains minor adhesion in urine was observed. This study demonstrates that the adhesion of lactobacilli to substrata differs with strain hydrophobicity and charge, and that urinary components can affect the ability of hydrophilic Lactobacillus strains to adhere to substrata.