Smart, Photothermally Activated, Antibacterial Surfaces with Thermally Triggered Bacteria-Releasing Properties

The development of effective antibacterial surfaces to prevent the attachment of pathogenic bacteria and subsequent bacterial colonization and biofilm formation is critically important for medical devices and public hygiene products. In the work reported herein, a smart antibacterial hybrid film based on tannic acid/Fe³⁺ ion (TA/Fe) complex and poly(N-isopropylacrylamide) (PNIPAAm) is deposited on diverse substrates. This surface is shown to have bacteria-killing and bacteria-releasing properties based on, respectively, near-infrared photothermal activation and subsequent cooling. The TA/Fe complex has three roles in this system: (i) as a universal adhesive "anchor" for surface modification, (ii) as a high-efficiency photothermal agent for ablation of attached bacteria (including multidrug resistant bacteria), and (iii) as a robust linker for immobilization of NH₂-terminated PNIPAAm via either Michael addition or Schiff base formation. Moreover, because of the thermoresponsive properties of the immobilized PNIPAAm, almost all of the killed bacteria and other debris can be removed from the surface simply by lowering the temperature. It is shown that this hybrid film can maintain good antibacterial performance after being used for multiple "kill-and-release" cycles and can be applied to various substrates regardless of surface chemistry or topography, thus providing a broadly applicable, simple, and reliable solution to the problems associated with surface-attached bacteria in various healthcare applications.

Characterization of Pseudomonas aeruginosa Films on Different Inorganic Surfaces before and after UV Light Exposure

The changes of the surface properties of Au, GaN, and SiO _x after UV light irradiation were used to actively influence the process of formation of Pseudomonas aeruginosa films. The interfacial properties of the substrates were characterized by X-ray photoelectron spectroscopy and atomic force microscopy. The changes in the P. aeruginosa film properties were accessed by analyzing adhesion force maps and quantifying the intracellular Ca²⁺ concentration. The collected analysis indicates that the alteration of the inorganic materials' surface chemistry can lead to differences in biofilm formation and variable response from P. aeruginosa cells.

Fabricating upconversion fluorescent nanoparticles modified substrate for dynamical control of cancer cells and pathogenic bacteria

Lanthanide-doped upconversion nanoparticles (UCNPs) have attracted widespread interests in the field of biomedicine because of their unique upconverting capability by converting near infrared (NIR) excitation to visible or ultraviolet (UV) emission. Here, we developed a novel UCNP-based substrate for dynamic capture and release of cancer cells and pathogenic bacteria under NIR-control. The UCNPs harvest NIR light and convert it to ultraviolet light, which subsequently result in the cleavage of photoresponsive linker (PR linker) from the substrate, and on demand allows the release of a captured cell. The results show that after seeding cells for 5 h, the cells were efficiently captured on the surface of the substrate and ˜89.4% of the originally captured S. aureus was released from the surface after exposure to 2 W/cm² NIR light for 30 min, and ˜92.1% of HepG2 cells. These findings provide a unique platform for exploring an entirely new application field for this promising luminescent nanomaterial.

Photoresponsive Cucurbit[8]uril-Mediated Adhesion of Bacteria on Supported Lipid Bilayers

In this work, the development of a photoresponsive platform for the presentation of bioactive ligands to study receptor-ligand interactions has been described. For this purpose, supramolecular host-guest chemistry and supported lipid bilayers (SLBs) have been combined in a microfluidic device. Quartz crystal microbalance with dissipation monitoring (QCM-D) studies on methyl viologen (MV)-functionalized oligo ethylene glycol-based self-assembled monolayers, gel and liquid-state SLBs have been compared for their nonfouling properties in the case of ConA and bacteria. In combination with bacterial adhesion test, negligible nonspecific bacterial adhesion is observed only in the case of methyl-viologen-modified liquid-state SLBs. Therefore, liquid-state SLBs have been identified as most suitable for studying specific cell interactions when MV is incorporated as a guest on the surface. The photoswitchable supramolecular ternary complex is formed by assembling cucurbit[8]uril (CB[8]) and an azobenzene-mannose conjugate (Azo-Man) onto MV-functionalized liquid-state SLBs and the assembly process has been characterized using QCM-D and fluorescence techniques. Mannose has been found to enable binding of E. coli via cell-surface receptors on the nonfouling supramolecular SLBs. Optical switching of the azobenzene moiety allows us to "erase" the bioactive surface after bacterial binding, providing the potential to develop reusable sensors. Localized photorelease of bacterial cells has also been shown indicating the possibility of optically guiding cellular growth, migration, and intercellular interactions.

Effect of UV-photofunctionalization on oral bacterial attachment and biofilm formation to titanium implant material

Bacterial biofilm infections remain prevalent reasons for implant failure. Dental implant placement occurs in the oral environment, which harbors a plethora of biofilm-forming bacteria. Due to its trans-mucosal placement, part of the implant structure is exposed to oral cavity and there is no effective measure to prevent bacterial attachment to implant materials. Here, we demonstrated that UV treatment of titanium immediately prior to use (photofunctionalization) affects the ability of human polymicrobial oral biofilm communities to colonize in the presence of salivary and blood components. UV-treatment of machined titanium transformed the surface from hydrophobic to superhydrophilic. UV-treated surfaces exhibited a significant reduction in bacterial attachment as well as subsequent biofilm formation compared to untreated ones, even though overall bacterial viability was not affected. The function of reducing bacterial colonization was maintained on UV-treated titanium that had been stored in a liquid environment before use. Denaturing gradient gel-electrophoresis (DGGE) and DNA sequencing analyses revealed that while bacterial community profiles appeared different between UV-treated and untreated titanium in the initial attachment phase, this difference vanished as biofilm formation progressed. Our findings confirm that UV-photofunctionalization of titanium has a strong potential to improve outcome of implant placement by creating and maintaining antimicrobial surfaces.

Ultrasound assisted biodesulfurization of liquid fuel using free and immobilized cells of Rhodococcus rhodochrous MTCC 3552: A mechanistic investigation

This paper attempts to gain mechanistic insight into enhancement effect of sonication on biodesulfurization. The approach has been to fit Haldane kinetics model to dibenzothiophene (DBT) metabolism and analyze trends in model parameters concurrently with simulations of cavitation bubble dynamics. Mechanistic synergy between sonication and biodesulfurization is revealed to be of both physical and chemical nature. Generation of micro-turbulence in medium by sonication leads to fine emulsification and enhancement of DBT transport across organic/aqueous interphase. Microturbulence also enhances transport of substrate and product across cell wall that increases reaction velocity (Vmax). Michaelis constant (Km) and inhibition constant (KI), being intrinsic parameters, remain unaffected by sonication. Radicals produced by transient cavitation oxidize DBT to DBT-sulfoxide and DBT-sulfone (intermediates of metabolism), which contributes enhancement of biodesulfurization. However, high shear generated by ultrasound and cavitation has adverse effect on action of surfactant β-cyclodextrin for enhancement of interphase transport of DBT.

Ultra-low power laser stimulation impairs the adhesion of Staphylococcus aureus to primary human cells, and interferes with the expression of staphylococcal pathogenic factors

Lasers are commonly used in several fields of medicine as a complementary therapy for internal medicine, surgery and also diagnostics. The efficacy of ultra-low level laser therapy (ULLLT) at power levels around 0.15 mW/cm(2) has been demonstrated both in in vitro experiments and in the clinical environment. This work used an ULLLT laser source to analyze its efficacy on Staphylococcus aureus adhesion to cells and on its ability to produce pathogenic factors. Laser stimulation succeeded in impairing the binding of S. aureus to primary human cells in culture and in inhibiting the expression of coagulase, one of the main staphylococcal pathogenic factors. The importance of the extracellular matrix (ECM) and the modification of the ECM redox potential in these activities were also evidenced.

Blue-violet laser modification of titania treated titanium: antibacterial and osteo-inductive effects

BACKGROUND

Many studies on surface modifications of titanium have been performed in an attempt to accelerate osseointegration. Recently, anatase titanium dioxide has been found to act as a photocatalyst that expresses antibiotic properties and exhibits hydrophilicity after ultraviolet exposure. A blue-violet semiconductor laser (BV-LD) has been developed as near-ultraviolet light. The purpose of this study was to investigate the effects of exposure to this BV-LD on surface modifications of titanium with the goal of enhancing osteoconductive and antibacterial properties.

METHODS

The surfaces of pure commercial titanium were polished with #800 waterproof polishing papers and were treated with anatase titania solution. Specimens were exposed using BV-LD (λ = 405 nm) or an ultraviolet light-emitting diode (UV-LED, λ = 365 nm) at 6 mW/cm(2) for 3 h. The surface modification was evaluated physically and biologically using the following parameters or tests: surface roughness, surface temperature during exposure, X-ray diffraction (XRD) analysis, contact angle, methylene blue degradation tests, adherence of Porphyromonas gingivalis, osteoblast and fibroblast proliferation, and histological examination after implantation in rats.

RESULTS

No significant changes were found in the surface roughness or XRD profiles after exposure. BV-LD exposure did not raise the surface temperature of titanium. The contact angle was significantly decreased, and methylene blue was significantly degraded. The number of attached P. gingivalis organisms was significantly reduced after BV-LD exposure compared to that in the no exposure group. New bone was observed around exposed specimens in the histological evaluation, and both the bone-to-specimen contact ratio and the new bone area increased significantly in exposed groups.

CONCLUSIONS

This study suggested that exposure of titanium to BV-LD can enhance the osteoconductivity of the titanium surface and induce antibacterial properties, similar to the properties observed following exposure to UV-LED.

Light regulates attachment, exopolysaccharide production, and nodulation in Rhizobium leguminosarum through a LOV-histidine kinase photoreceptor

Rhizobium leguminosarum is a soil bacterium that infects root hairs and induces the formation of nitrogen-fixing nodules on leguminous plants. Light, oxygen, and voltage (LOV)-domain proteins are blue-light receptors found in higher plants and many algae, fungi, and bacteria. The genome of R. leguminosarum bv. viciae 3841, a pea-nodulating endosymbiont, encodes a sensor histidine kinase containing a LOV domain at the N-terminal end (R-LOV-HK). R-LOV-HK has a typical LOV domain absorption spectrum with broad bands in the blue and UV-A regions and shows a truncated photocycle. Here we show that the R-LOV-HK protein regulates attachment to an abiotic surface and production of flagellar proteins and exopolysaccharide in response to light. Also, illumination of bacterial cultures before inoculation of pea roots increases the number of nodules per plant and the number of intranodular bacteroids. The effects of light on nodulation are dependent on a functional lov gene. The results presented in this work suggest that light, sensed by R-LOV-HK, is an important environmental factor that controls adaptive responses and the symbiotic efficiency of R. leguminosarum.

Immobilization of magnetic modified Flavobacterium ATCC 27551 using magnetic field and evaluation of the enzyme stability of immobilized bacteria

The magnetic modified Flavobacterium sp. was prepared by covalently binding carboxylate-modified magnetic nanoparticles, and also, ionic adsorption of magnetic Fe(3)O(4) nanoparticles on the cell surface. The magnetic modified bacteria were immobilized by both internal and external magnetic fields. The pH stability and inherent resistance of the enzyme activity of the immobilized bacteria under acidic and alkaline conditions were increased. Immobilization of the magnetic modified bacteria using an external magnetic field improved the enzyme thermal stability. The results revealed that immobilization of the magnetic modified bacteria by an external magnetic field keeps 50% of the enzyme activity after 23.4, 16.6 and 6 h of incubation at 55 °C for the covalently binding of magnetic nanoparticles, the ionic adsorption of magnetic nanoparticles and the free cells, respectively. The results demonstrated the negative effect of various magnetic beads on the enzyme thermal stability of immobilized magnetic modified bacteria using an internal magnetic field.

[Influence of electromagnetic emission at the frequencies of molecular absorption and emission spectra of oxygen and nitrogen oxide on the adhesion and formation of Pseudomonas aeruginosa biofilm]

AIM

Evaluate the influence of electromagnetic emission (EME) at the frequencies of molecular absorption and emission spectra of atmospheric oxygen and nitrogen oxide (MAES 02 and MAES NO respectively) on the adhesion, population progress and biofilm formation of Pseudomonas aeruginosa.

MATERIALS AND METHODS

Adhesive activity was evaluated by mean adhesion index (MAI) of bacteria on human erythrocytes. Population growth dynamic was assessed by optical density index of broth cultures; biofilm formation--by values of optical density of the cells attached to the surface of polystyrol wells.

RESULTS

P.aeruginosa bacteria had high adhesive properties that have increased under the influence of MAES 02 frequency emission and have not changed under the influence of MAES NO frequency. Exposure of bacteria to MAES NO frequency did not influence the population progress; exposure to MAES 02 frequency stimulated the biofilm formation ability of the bacteria, and MAES NO--decreased this ability.

CONCLUSION

EME at MAES NO frequency can be used to suppress bacterial biofilm formation by pseudomonas.

Efficacy of UV treatment in the management of bacterial adhesion on hard surfaces

The efficacy of UV treatment to control bacterial adhesion onto hard surfaces was investigated in laboratory conditions. The major characteristics necessary for biofilm formation like extracellular polymeric substance (EPS) production, carbohydrate and protein concentration in EPS, and adhesion ability onto hard surface were studied using two bacterial strains isolated from marine biofilms. The results showed that there was a considerable difference between the control and UV treated bacterial cultures in their viability, production of EPS, and adhesion ability. The protein and carbohydrate concentration of the EPS and the adhesion of bacterial cells to surface were also considerably reduced due to UV treatment. This study indicates that treatment of water with UV light may be used to control biofilm development on hard surfaces.

Photocatalytic inactivation of E. coli with a mesoporous TiO2 coated film using the film adhesion method

The photocatalytic inactivation of Escherichia coli with the film adhesion method by using Degussa P25TiO2 and mesoporous TiO2 coated on glass was investigated. Monodisperse spherical mesoporous TiO2 with a morphology size of approximately 800 nm was synthesized via the sol-gel approach and coated onto glass substrates without cracking by using the doctor blade method with various amounts of polyethylene oxide (PEO) and polyethylene glycol (PEG). Photocatalytic disinfection was tested by varying the UV-A light intensity, cell concentration, and UV-A irradiation time. The photocatalytic inactivation achieved with mesoporous TiO2 was found to be higher than that with the commercial P25TiO2. Byvarying the surface area and crystallite size of mesoporous TiO2 through control of the calcination temperature, we found that the efficacy of photocatalytic disinfection with the film adhesion method is strongly dependent on the surface area and crystallite size: the larger the surface area and the smaller the crystallites, the higher the efficacy of photocatalytic inactivation.

Laser trap studies of end-on E. coli adhesion to glass

Rod-shaped Escherichia coli K12:D21 bacteria were previously found to adhere by their ends (poles) [J.F. Jones, J.D. Feick, D. Imoudu, N. Chukwumah, M. Vigeant, D. Velegol, Appl. Environ. Microbiol. 69 (2003) 6515.]. In the current study we used a Nd:YAG 1064 nm laser trap to quantify the fraction of adherent bacteria and the time scale for the adhesion to occur. For the E. coli studied, 15.9+/-3.4% of the bacteria adhered when presented end-on for 15s to a cleaned glass surface that was not treated for specific interactions. These bacteria were found to adhere either instantaneously (approximately <1s) or not at all, and the adhesion was shown to be independent of power (force) of the laser trap. Additionally, for a given bacterium, either 0 or 1 ends were adhesive, never both ends. It is hypothesized that the end-on adhesion of D21 is related to bacterial polarity that dynamically results from the division process. We studied the reattachment of cells after adhesion and subsequent removal, finding that most bacteria reattach, some at least five times. However, a small fraction of D21 did not reattach after the first removal. Bacterial cells with observable division planes were tested for end-on adhesion; none of the 18 cells studied adhered by either end. On the other hand, we examined 50 daughter cells immediately after division, and four of the cells were adhesive. End-on adhesion is shown to be an important initial adhesion strategy for the E. coli strain via a single end with adhesion occurring instantaneously. Knowledge about adherent nanodomains (here, on one end) on bacteria will lead to better predictions of sticking coefficients and bacteria transport through porous media.

Escherichia coli control in a surface flow treatment wetland

A field experiment showed that numbers of Escherichia coli declined significantly when floating Lemna spp. plants were removed to create open water areas in a typical newly constructed surface flow treatment wetland in southern Ontario. It is suggested that E. coli declined immediately after Lemna removal because the Lemna was shading the water column from penetration by natural UV radiation, it was providing favourable attachment sites for the E. coli, and it was not allowing effective free exchange of oxygen from surface winds to the water column to maintain high enough dissolved oxygen supplies for predator zooplankton populations. Operators of wetland systems must have the specialized skills required to recognize the cause and the appropriate maintenance requirements to maintain efficient operation of such unconventional systems should E. coli numbers increase during the course of operation.

Externalization of host cell protein kinase C during enteropathogenic Escherichia coli infection

Enteropathogenic Escherichia coli (EPEC) is a common cause of diarrhea in children in developing countries. Protein kinase C (PKC), a serine- and threonine-directed protein kinase, is rapidly activated following EPEC infection and this is accompanied by its translocation to a membrane-bound location where it is tightly bound to phosphatidylserine (PS). EPEC infection causes host cell death, one of whose features is externalization of PS. We hypothesized that externalization of PS would be accompanied by externalization of PKC as well. We report that EPEC infection triggers the externalization of PKC to the outer surface of the host cell. Ecto-PKC remains firmly tethered to the cell but can be released by incubation with peptide or protein substrates for the enzyme. Ecto-PKC is intact and biologically active and able to phosphorylate protein substrates on the surface of the host cell. Phosphorylation of whole EPEC bacteria or EPEC-secreted proteins could not be detected. Externalization of PKC could be reproduced by the combination of an apoptotic stimulus (ultraviolet (UV) irradiation) and phorbol myristate acetate (PMA), a procedure which resulted in externalization of >25% of the total cellular content of PKC-alpha. In the presence of ATP, ecto-PKC inhibited UV-induced cell shrinkage, membrane blebbing, and propidium iodide uptake but not the activation of caspases 3 and 7. This is the first report that expression of an ecto-protein kinase is altered by a microbial pathogen and the first to note that externalization of PKC can accompany apoptosis.

Surface characteristics of spacecraft components affect the aggregation of microorganisms and may lead to different survival rates of bacteria on Mars landers

Layers of dormant endospores of Bacillus subtilis HA101 were applied to eight different spacecraft materials and exposed to martian conditions of low pressure (8.5 mbar), low temperature (-10 degrees C), and high CO(2) gas composition and irradiated with a Mars-normal ultraviolet (UV-visible- near-infrared spectrum. Bacterial layers were exposed to either 1 min or 1 h of Mars-normal UV irradiation, which simulated clear-sky conditions on equatorial Mars (0.1 tau). When exposed to 1 min of Mars UV irradiation, the numbers of viable endospores of B. subtilis were reduced three to four orders of magnitude for two brands of aluminum (Al), stainless steel, chemfilm-treated Al, clear-anodized Al, and black-anodized Al coupons. In contrast, bacterial survival was reduced only one to two orders of magnitude for endospores on the non-metal materials astroquartz and graphite composite when bacterial endospores were exposed to 1 min of Mars UV irradiation. When bacterial monolayers were exposed to 1 h of Mars UV irradiation, no viable bacteria were recovered from the six metal coupons listed above. In contrast, bacterial survival was reduced only two to three orders of magnitude for spore layers on astroquartz and graphite composite exposed to 1 h of Mars UV irradiation. Scanning electron microscopy images of the bacterial monolayers on all eight spacecraft materials revealed that endospores of B. subtilis formed large aggregates of multilayered spores on astroquartz and graphite composite, but not on the other six spacecraft materials. It is likely that the formation of multilayered aggregates of endospores on astroquartz and graphite composite is responsible for the enhanced survival of bacterial cells on these materials.

Surface bio-magnetism on bacterial cells adhesion and surface proteins secretion

Extensive research works have been done on using magnetic fields on biological organism, but the results till date have been controversial [D.O. Carpenter, S. Ayrapetyan (Eds.), Biological Effects of Electric and Magnetic Fields, vol. 1, Academic Press, San Diego, 1994]. In spite of this, the study of surface magnetic effects on bacterial adhesion and cell growth has not been rigorously explored. The effects of surface magnetism, using perpendicularly polarized magnetic media, are evaluated on Bacillus licheniformis, a widely used bacterium in brewery [L. Kandra, a-Amylases of medical and industrial importance. J. Mol. Struct. (Theochem.), in press] and pharmaceutical [H. Ikram-ul et al., Production of alph amylase by Bacillus licheniformis using an economical medium. Bioresour. Technol. 87 (2003) 57-61] industries, by observing its adhesion and growth behavior. At different spin directions, we are able to observe a change on the biofilm formation, protein synthesis, and cell growth rate. Given that surface energy can easily penetrate through cells, this approach is an advantage over existing techniques that require direct physical contact to target cells. It also presents a new technique to cell adhesion and synthesis of surface proteins.

The impact of ultraviolet light on bacterial adhesion to glass and metal oxide-coated surface

Biofouling of glass and quartz surfaces can be reduced when the surface is coated with photocatalytically active metal oxides, such as TiO2 (anatase form) or SnO2. We measured the attachment of eight strains of bacteria to these two metal oxides (TiO2 and SnO2), and to an uncoated glass (control; designated Si-m) before and after exposure to UV light at wavelengths of 254 nm (UVC) or 340 nm UV (UVA). TiO2-coated surfaces were photocatalytically active at both 254 and 340 nm as evidenced by a decrease in the water contact angle of the surface from 59 degrees +/-2 to <5 degrees. The water contact angle of the SnO2 surface was reduced only at 254 nm, while contact angle of the Si-m glass surface was not altered by light of either wavelength. Bacterial adhesion decreased by 10-50% to photocatalyzed glass surfaces. In all cases, bacteria exposed to the UV light were completely killed due to a combination of exposure to UV light and the photocatalytic activity of the glass surfaces. These results show that UV light irradiation of TiO2-coated surfaces can be an effective method of reducing bacterial adhesion.

Construction of biofilms with defined internal architecture using dielectrophoresis and flocculation

A novel approach was developed for the construction of biofilms with defined internal architecture using AC electrokinetics and flocculation. Artificial structured microbial consortia (ASMC) consisting of localized layered microcolonies of different cell types were formed by sequentially attracting different cell types to high field regions near microelectrodes using dielectrophoresis. Stabilization of the microbial consortia on the electrode surface was achieved by crosslinking the cells using the flocculant polyethyleneimine (PEI). Consortia of Escherichia coli, Micrococcus luteus, and Saccharomyces cerevisiae were made as model systems. Also, more natural consortia were made of the bacteria Pseudomonas putida, Clavibacter michiganense, and Methylobacterium mesophilum, which are found together in consortia during biodegradation of metal-cutting waste fluids.

Laser impact assessment in a biofilm-forming bacterium Pseudoalteromonas carrageenovora using a flow cytometric system

Impact by pulsed laser irradiations from an Nd:YAG laser on the marine biofilm-forming bacterium Pseudoalteromonas carrageenovora has been studied using a flow cytometric system. The biofilm-forming bacteria in the planktonic state have been irradiated while flowing, and the mortality and bacterial attachment have been determined by exposing TiN coupons in the system. Coupons suspended in the non-irradiated bacterial flow were treated as the control. The fluence used in the study was 0.1 J/cm(2). Three flow rates (14, 28, and 42 cm/min) and two exposure durations (15 and 30 min) were tested. The results showed the increase in bacterial mortality with the decrease in flow rate. The maximum mortality of 27.5% was observed when the flow rate was 14 cm/min. The bacterial attachment increased with the increase in flow rate and exposure duration. The area of bacterial attachment on the experimental coupons exposed to the irradiated sample was significantly lesser than that for the nonirradiated sample. The results thus show in a flowing system, low power pulsed laser irradiations could reduce the bacterial attachment even though it did not cause significant mortality.

Preparation of a colored conductive paint electrode for electrochemical inactivation of bacteria

In this study we describe the preparation of a colored conductive paint electrode containing In(2)O(3), SnO(2), or TiO(2) for the electrochemical inactivation of marine bacteria. When each colored conductive paint electrode was immersed in seawater containing 10(6) cells/mL for 90 min, marine microbe attachment to the TiO(2)/SnO(2)/Sb electrode surface was minimal. Preparation of electrodes coated with 40% particles is shown to be more cost-effective, and because of their more translucent coatings they can be painted over with bright colors. When a potential of 1.0 V was applied for 30 min to the colored conductive paint electrode (40 wt% TiO(2)/SnO(2)/Sb) in sterile seawater, the survival ratio decreased to 55%. When 1.5 V vs. saturated calomel electrode (SCE) was applied, all attached cells were inactivated. Chlorine was not detected below an applied potential of 1.5 V. A change in pH was not observed in the range of 0 to 1.5 V. This method might be effective for preventing bacterial cell accumulation and the formation of biofilms.

Ultrasound increases the rate of bacterial cell growth

Ultrasound was employed to increase the growth rate of bacterial cells attached to surfaces. Staphylococcus epidermidis, Pseudomonas aeruginosa, and Escherichia coli cells adhered to and grew on a polyethylene surface in the presence of ultrasound. It was found that low-frequency ultrasound (70 kHz) of low acoustic intensity (<2 W/cm(2)) increased the growth rate of the cells compared to growth without ultrasound. However, at high intensity levels, cells were partially removed from the surface. Ultrasound also enhanced planktonic growth of S. epidermidis and other planktonic bacteria. It is hypothesized that ultrasound increases the rate of transport of oxygen and nutrients to the cells and increases the rate of transport of waste products away from the cells, thus enhancing their growth.

Complex effects of pulsed infrared laser and asparaginase on Escherichia coli strains isolated from patients with urinary diseases

Treatment with L-asparaginase and low-frequency laser decreased adhesion of uropathogenic Escherichia coli to human erythrocytes. The maximum effect was observed after combined treatment (laser exposure followed by enzyme treatment).

Adhesion of inactivated probiotic strains to intestinal mucus

It has been suggested that probiotics should be viable in order to elicit beneficial health effects. Inactivation of probiotics has been suggested to interfere with the binding to the mucosa and thereby with the immune modulating activity of probiotics. The effect of different inactivation methods on the mucus adhesion of nine probiotic strains was studied. Inactivation by heat or gamma-irradiation generally decreased the adhesive abilities. However, heat treatment increased the adhesion of Propionibacterium freudenreichii and gamma-irradiation enhanced the adhesion of Lactobacillus casei Shirota. Inactivation by u.v. was not observed to modulate the adhesion of the tested strains and it was concluded to be the most appropriate method for studying non-viable probiotics and preparing control products.

Elimination of bacteria on different implant surfaces through photosensitization and soft laser. An in vitro study

Microbiologic examinations of implants have shown that certain microorganisms described as periodontal pathogens may have an influence on the development and the progression of peri-implant disease. This experimental study aimed to examine the bactericidal effect of irradiation with a soft laser on bacteria associated with peri-implantitis following exposure to a photosensitizing substance. Platelets made of commercially pure titanium, either with a machined surface or with a hydroxyapatite or plasma-flame-sprayed surface or with a corundum-blasted and etched surface, were incubated with a pure suspension of Actinobacillus actinomycetemcomitans or Porphyromonas gingivalis or Prevotella intermedia. The surfaces were then treated with a toluidine blue solution and irradiated with a diode soft laser with a wave length of 905 nm for 1 min. None of the smears obtained from the thus treated surfaces showed bacterial growth, whereas the smears obtained from surfaces that had been subjected to only one type of treatment showed unchanged growth of every target organism tested (P < 0.0006). Electron microscopic inspection of the thus treated platelets revealed that combined dye/laser treatment resulted in the destruction of bacterial cells. The present in vitro results indicate that lethal photosensitization may be of use for treatment of peri-implantitis.

A model study of factors involved in adhesion of Pseudomonas fluorescens to meat

A study was undertaken to investigate the factors involved in the adhesion of Pseudomonas fluorescens to model meat surfaces (tendon slices). Adhesion was fast (less than 2.5 min) and was not suppressed by killing the cells with UV, gamma rays, or heat, indicating that physiological activity was not required. In various salt solutions (NaCl, KCl, CaCl2, MgCl2), adhesion increased with increasing ionic strength up to 10 to 100 mM, suggesting that, at low ionic strengths, electrostatic interactions were involved in the adhesion process. At higher ionic strengths (greater than 10 to 100 mM) or in the presence of Al3+ ions, adhesion was sharply reduced. Selectively blocking of carboxyl or amino groups at the cell surface by chemical means did not affect adhesion. These groups are therefore not directly involved in an adhesive bond with tendon. Given a sufficient cell concentration (10(10) CFU.ml-1) in the adhesion medium, the surface of tendon was almost entirely covered with adherent bacteria. This suggests that if the adhesion is specific, the attachment sites on the tendon surface must be located within collagen or proteoglycan molecules.

Characterization of Borrelia burgdorferi invasion of cultured endothelial cells

Borrelia burgdorferi can adhere to cultured endothelial cells and penetrate through cell monolayers by passing through intercellular tight junctions and through the host cell cytoplasm. Borrelia burgdorferi strains which were isolated from different sources and areas of the U.S. all demonstrated similar invasive capabilities. Bacterial penetration from the apical to the basal surface of the monolayer was 20 times more efficient than from the basal to the apical surface. Borreliae which were non-viable as a result of either heat treatment or ultraviolet (UV) irradiation showed reduced association with the endothelial cell monolayer and loss of invasive capabilities. Borreliae were able to invade when protein synthesis was inhibited with streptomycin or chloramphenicol. When assays were conducted at 4 degrees C, bacterial penetration of the monolayer was completely inhibited. Treatment of borreliae with proteases affecting outer surface proteins greatly reduced cell association and bacterial invasion.

Bacterial adhesion to medical polymers--use of radiation techniques for the prevention of materials-associated infections

The basic principles of the adhesion of bacteria to polymer surfaces are discussed, as the first important step in the pathogenesis of foreign-body infections. Strategies for the prevention of foreign-body infections by polymer modification with ionizing radiation are presented. These include the modification of polymer surfaces by radiation or glow discharge techniques to obtain antiadhesive or antimicrobial surfaces, as well as the fixation or incorporation of antibiotic drugs to or into the polymer.

The adhesin structures involved in the adherence of group B streptococci to human vaginal cells

The adherence of group B streptococci (GBS) of serotypes Ia, II and III to human vaginal cells was studied in vitro. The adherence was not dependent on the viability of bacteria; killing of GBS by UV irradiation or glutaraldehyde treatment did not inhibit the adherence. Killing of GBS by heating to 56 degrees C for 1 h led to a pronounced decrease of adherence, demonstrating the thermosensitivity of the GBS structures involved. The protein nature of these structures was proved by a significant reduction of adherence after pretreatment of GBS with trypsin or pepsin. Pretreatment of GBS with sialidase had no influence on the adherence. Such a pretreatment of vaginal cells caused an increase of adherence showing that the receptors on epithelial cells may be partly masked by sialic acid.