Stochastic modeling of bacterial adhesion: a two-step mechanism with linear adhesion rate

Stochastic analysis of bacterial adhesion onto the surface of solid substrate is presented. Bacterial adhesion is assumed to occur in two steps: (i) a reversible adhesion between bacteria and solid surface; bacteria on the surface are weakly bound during this period, followed by (ii) an irreversible surface reaction which results in a strong binding force between bacteria and the surface; bacteria are considered to be in adhered form at this stage. The stochastic representation provides both the macroscopic and fluctuating information about the transient behavior of the phenomenon under consideration.     

Effect of Air Plasma Processing on the Adsorption Behaviour of Bovine Serum Albumin on Spin-Coated PMMA Surfaces

This paper reports the adsorption of Bovine Serum Albumin （BSA） onto Dielectric Barrier Discharge （DBD） processed Poly（methyl methacrylate） （PMMA） surfaces by a Quartz Crystal Microbalance with Dissipation monitoring （QCM-D） technique. The purpose is to study the influence of DBD processing on the nature and scale of BSA adsorption on PMMA surface in vitro. It was observed that DBD processing improves the surface wettability of PMMA film, a fact attributable to the changes in surface chemistry and topography. Exposure of the PMMA to Phosphate Buffed Saline （PBS） solution in the QCM-D system resulted in surface adsorption which reaches an equilibrium after about 30 minutes for pristine PMMA, and 90 minutes for processed PMMA surface. Subsequent injection of BSA in PBS indicated that the protein is immediately adsorbed onto the PMMA surface. It was revealed that adsorption behaviour of BSA on pristine PMMA differs from that on processed PMMA surface. A slower adsorption kinetics was observed for pristine PMMA surface, whilst a quick adsorption kinetics for processed PMMA. Moreover, the dissipation shift of protein adsorption suggested that BSA forms a more rigid structure on pristine PMMA surface that on processed surface. These data suggest that changes in wettability and attendant chemical properties and surface texture of the PMMA surface may play a significant role in BSA adsorption process.     

Different microbial biofilm formation on polymethylmethacrylate (PMMA) bone cement loaded with gentamicin and vancomycin

We studied the in vitro effects of gentamicin and vancomycin alone and in combination added to polymethylmethacrylate (PMMA) cement specimens on the bacterial adhesion of multiresistant clinical isolates.The PMMA specimens (discs) loaded with gentamicin (1.9%) or vancomycin (1.9%) or with a combination of the two were placed in Mueller-Hinton Broth inoculated with bacterial strains. After incubation, bacterial growth was determined by optical density (OD₅₄₀) and sub-cultures. The biofilm PMMA-associated dye (crystal violet) was measured. Antibiotic concentrations in broth were determined by fluorescence polarisation immunoassay.All antibiotic-loaded PMMA cement specimens released high, inhibitory concentrations of gentamicin and vancomycin. However, differences in strain growth and adhesion were recorded. The clinical isolates Met-R/Gent-R CoNS showed no adhesion to gentamicin-loaded specimens for 24 h; strains with Gent-Intermediate susceptibility exhibited growth after 48 h but reduced adhesion. Some Gent-R strains exhibited growth and adhesion to antibiotic-loaded specimens similar to controls (plain discs). Only the VRSA strain (Staphylococcus aureus 5/7) and Escherichia coli were able to grow and adhere to vancomycin-loaded specimens after 24 h of incubation. The specimens loaded with the gentamicin + vancomycin combination showed a synergistic inhibitory effect against all tested strains (no bacterial growth). The degree of bacterial adhesion to PMMA cement loaded with gentamicin or vancomycin may be reduced in spite of a normal growth rate and is different for the tested strains.The effect of gentamicin and vancomycin on bacterial growth and adhesion to PMMA bone cement depends on the antibiotic concentrations, on the characteristics of each specific strain and on its ability to produce biofilm and adhere to antibiotic-loaded PMMA bone cement.     

Inhibition de l'adhérence de Porphyromonas gingivalis sur la surface de titane greffé de poly(styrène sulfonate de sodium)

Dental implant-associated infections as peri-implantitis represent one of the major causes of osteointegration failures of oral implants. Adhesion of Porphyromonas gingivalis, one of the bacterial strains mainly involved in such infections, is tightly dependent on the topographical and/or physico-chemical properties of the implant surfaces. As a matter of fact, we showed that the grafting of one bioactive polymer such as poly(sodium styrene sulfonate) onto titanium implant surfaces allowed a sensitive decrease of Staphylococcus aureus adhesion (> 40%). The aim of the study consists in evaluating the adhesion of P. gingivalis onto titanium surfaces grafted with poly(sodium stryrene sulfonate) in order to elaborate implants exhibiting appropriate inhibiting properties towards the adhesion of periodontal pathogens. The grafting of poly(sodium stryrene sulfonate) onto titanium surfaces is carried out in two steps: chemical oxydation of titanium to initiate radical species then grafting of poly(sodium stryrene sulfonate) by radical polymerization. Chemical characterization of the surfaces is achieved by Fourier transformed infrared spectroscopy (FTIR). Bacterial adhesion was studied on grafted and non grafted (control) titanium surfaces, preadsorbed or not by plasmatic proteins. Protein adsorption as well as bacteria adhesion is followed by fluorescence spectroscopy by using proteins or bacteria previously labelled with fluorescence probes; the quantification of adsorption and bacteria adhesion are performed by image analysis. Results showed that protein adsorption is more important (~3 times) and that P. gingivalis adhesion is strongly inhibited (~73%) onto poly(sodium styrene sulfonate) grafted surfaces when compared to titanium control. Moreover, the inhibition of bacterial adhesion on grafted surfaces preadsorbed with plasma proteins is comparable to that observed on grafted surfaces preadsorbed with fibronectin. In conclusion, the obtained results evidenced that the grafting of titanium surface by poly(sodium styrene sulfonate) led to significant inhibition of P. gingivalis adhesion and that this inhibitory activity involved adsorbed proteins. Poly(sodium styrene sulfonate) grafted titanium surfaces present a high interest for the elaboration of oral implants in various clinical dental applications.     

The use of graft copolymers to inhibit the adhesion of bacteria to solid surfaces

Twelve graft copolymers have been evaluated for their ability to prevent the adhesion of bacteria to substrata. The copolymers had polyethylene glycol (PEG) side-chains (‘teeth’) and a backbone that was either uncharged, acidic, basic or amphoteric. The copolymers were adsorbed onto glass, stainless steel and hydroxyapatite substrata, and 2-hpetri-dish adhesion experiments performed with bacteria isolated from marine (Pseudomonas sp. NCMB 2021), paper mill (S. marcescens NCIB 12211) and oral (S. mutans NCTC 10449) environments. The copolymers containing the most charged groups in the backbone had the most significant effect on bacterial adhesion levels, with anti-adhesive effects up to 99% achieved. An amphoteric copolymer (Compound 12) on glass, and acidic copolymer (Compound 11) on stainless steel and hydroxyapatite gave the most impressive anti-adhesive effects. These copolymers had non-specific bacterial anti-adhesive properties.It is proposed that the graft copolymers adsorbed onto hydrophilic surfaces via their charged backbone in such a way that the PEG side-chains were pointing out into the aqueous phase, and it was this orientation that was responsible for the observed anti-adhesive effect.     

Adsorption behavior and activity of horseradish peroxidase onto polysaccharide-decorated particles

The adsorption behavior of horseradish peroxidase (HRP) onto hybrid particles of poly(methylmethacrylate) (PMMA) and carboxymethylcellulose (CMC) was investigated by means of spectrophotometry. Dispersions of PMMA/CMC particles were characterized by light scattering, zeta potential measurements and scanning electron microscopy before and after HRP adsorption. HRP adsorbed irreversibly onto PMMA/CMC particles; the adsorption isotherm showed an initial step and an adsorption plateau. The enzymatic activity of free HRP and immobilized HRP (plateau region) was monitored by means of spectrophotometry as a function of storing time. Upon adsorbing HRP there is little (up to 20%) or no reduction of enzymatic activity in comparison to that observed for free HRP in solution. After storing free HRP and HRP-covered PMMA/CMC particles for 18 days the level of enzymatic activity is kept. HRP-covered PMMA/CMC particles dispersions, which were dried and re-dispersed, retained 50% of their catalytic properties. These interesting findings were discussed in the light of a beneficial effect of a hydrated microenvironment for maintenance of enzyme conformation and activity.     

Anaerobic saccharolytic bacterial adhesion to raw starch granules

The experiment of bacteria adhesion onto starch granules is conducted. It is found that anaerobic saccharolytic bacteria have the highest adhesion ability in their growth and initial stage of stationary phase. Starch granules with a low crystallinity, low bulk density, and high water-holding capacity have a high adhesion capacity. The optimum temperature for both bacterial growth and their adhesion is 30 degrees C. The optimum pH for the bacterial adhesion range from 5.0 to 6.5. Anaerobic conditions cause an appreciable decrease in percentage of adhesion. The percentage of adhesion is not sensitive to the type of soluble saccharide on which bacteria were grown.     

Comparison of the adherence of three Lactobacillus strains to Caco-2 and Int-407 human intestinal cell lines

F. SAREM, L.O. SAREM-DAMERDJI AND J.P. NICOLAS. 1996. Adhesion of three Lactobacillus strains onto human epithelial intestinal Caco-2 and Int-407 cell lines was compared. More adhesion occurred onto Int-407. The trypsin and sodium periodate pretreatment of bacteria revealed different mechanisms of adhesion depending on the Caco-2 and Int-407, involving carbohydrates and proteins. The absence of adherence for one Lactobacillus strain onto both cell lines indicated the specificity of the adhesion. Electron microscopic observations showed that bacteria adhered by underlying the brush border microvilli of the Caco-2 surface contrasting onto the Int-407 which entrapped and surrounded them by fimbrial extracellular cell matrix material.     

两种树脂基托细菌粘附情况的比较

目的比较BPS注塑树脂和热凝基托树脂表面细菌粘附能力的大小。方法将BPS注塑树脂和热凝基托树脂试件进行细菌体外粘附实验,采用菌落形成单位计数法测定血型链球菌、粘性放线菌和白色念珠菌粘附量的大小。结果培养24h、48h、168h后,各BPS注塑树脂试件组的细菌粘附量均少于热凝基托树脂试件组。结论BPS注塑树脂较热凝基托树脂更能减少血型链球菌、粘性放线菌和白色念珠菌在其表面的粘附。     

Activity,conformation and dynamics of cutinase adsorbed on poly(methyl methacrylate) latex particles

The adsorption of a recombinant cutinase from Fusarium solani pisi onto the surface of 100 nm diameter poly(methyl methacrylate) (PMMA) latex particles was evaluated. Adsorption of cutinase is a fast process since more than 70% of protein molecules are adsorbed onto PMMA at time zero of experiment, irrespective of the tested conditions. A Langmuir-type model fitted both protein and enzyme activity isotherms at 25 degrees C. Gamma(max) increased from 1.1 to 1.7 mg m(-2) and U(max) increased from 365 to 982 U m(-2) as the pH was raised from 4.5 to 9.2, respectively. A decrease (up to 50%) in specific activity retention was observed at acidic pH values (pH 4.5 and 5.2) while almost no inactivation (eta(act) congruent with 87-94%) was detected upon adsorption at pH 7.0 and 9.2. Concomitantly, far-UV circular dichroism (CD) spectra evidenced a reduction in the alpha-helical content of adsorbed protein at acidic pH values while at neutral and alkaline pH the secondary structure of adsorbed cutinase was similar to that of native protein. Fluorescence anisotropy decays showed the release of some constraints to the local motion of the Trp69 upon protein adsorption at pH 8.0, probably due to the disruption of the tryptophan-alanine hydrogen bond when the tryptophan interacts with the PMMA surface. Structural data associated with activity measurements at pH 7.0 and 9.2 showed that cutinase adsorbs onto PMMA particles in an end-on orientation with active site exposed to solvent and full integrity of cutinase secondary structure. Hydrophobic interactions are likely the major contribution to the adsorption mechanism at neutral and alkaline pH values, and a higher amount of protein is adsorbed to PMMA particles with increasing temperature at pH 9.2. The maximum adsorption increased from 88 to 140 mg cutinase per g PMMA with temperature raising from 25 to 50 degrees C, at pH 9.2.     

The Design of Simple Bacterial Microarrays: Development towards Immobilizing Single Living Bacteria on Predefined Micro-Sized Spots on Patterned Surfaces

In this paper we demonstrate a procedure for preparing bacterial arrays that is fast, easy, and applicable in a standard molecular biology laboratory. Microcontact printing is used to deposit chemicals promoting bacterial adherence in predefined positions on glass surfaces coated with polymers known for their resistance to bacterial adhesion. Highly ordered arrays of immobilized bacteria were obtained using microcontact printed islands of polydopamine (PD) on glass surfaces coated with the antiadhesive polymer polyethylene glycol (PEG). On such PEG-coated glass surfaces, bacteria were attached to 97 to 100% of the PD islands, 21 to 62% of which were occupied by a single bacterium. A viability test revealed that 99% of the bacteria were alive following immobilization onto patterned surfaces. Time series imaging of bacteria on such arrays revealed that the attached bacteria both divided and expressed green fluorescent protein, both of which indicates that this method of patterning of bacteria is a suitable method for single-cell analysis.     

Polymeric supports for the adhesion of a consortium of autotrophic nitrifying bacteria

The nitrifying performance of the biofilm formed onto polymeric supports (high density polystyrene, polyethylene, polypropylene, polyvinylchloride and polymethyl-methacrylate) was correlated with the hydrophobicity and surface charge of both bacteria and support media. Polypropylene , the most hydrophobic material, had the best properties for biofilm formation. The adhesion of nitrifying bacteria was mainly governed by hydrophobic interactions though electrostatic interactions were a determinant when the supports had identical hydrophobicity.     

Adhesion of oral streptococci from a flowing suspension to uncoated and albumin-coated surfaces

A flow cell system was developed which allowed the study of bacterial adhesion to solid substrata at well-defined shear rates. In addition, the system enabled the solid surfaces to be coated with a proteinaceous film under exactly the same shear conditions. In this flow cell system, adhesion of three strains of oral streptococci from a phosphate-buffered solution onto three different substrata was studied as a function of time in the absence and presence of a bovine serum albumin (BSA) coating at a shear rate of 21 s-1. To obtain a wide range in surface free energies (gamma) representative strains (gamma b 38-117 mJ m-2) and solid substrata (gamma s 20-109 mJ m-2) were selected. The number of bacteria adhering was counted microscopically. In the absence of a BSA coating a linear relation was found between the number of bacteria adhering at saturation (nb,s) and the calculated interfacial free energy of adhesion (delta Fadh) for each of the three strains. In the presence of a BSA coating the number of bacteria adhering was greatly decreased in all cases. However, despite the presence of the BSA coating there was still a linear relation between the number of bacteria adhering at saturation and the interfacial free energy of adhesion, calculated on the basis of the surface free energy of the uncoated substrata. It can be concluded that the bare, uncoated substratum still influenced bacterial adhesion in spite of the marked influence of a BSA coating.     

The role of bacterial hydrophobicity in infection: bacterial adhesion and phagocytic ingestion

The role that bacterial surface hydrophobicity (surface tension) plays in determining the extent of adhesion of polymer substrates and phagocytic ingestion is reviewed. The early attachment phase in bacterial adhesion is shown to depend critically on the relative surface tensions of the three interacting phases; i.e., bacteria, substrate, and suspending liquid surface tension. When suspended in a liquid with a high surface tension such as Hanks balanced salt solution, the most hydrophobic bacteria adhere to all surfaces to the greatest extent. When the liquid surface tension (gamma LV) is larger than the bacterial surface tension (gamma BV), then for any single bacterial species the extent of adhesion decreases with increasing substrate surface tension (gamma SV). When gamma LV less than gamma BV then adhesion increases with increasing gamma SV. Bacterial surface tension also determines in part the extent of phagocytic ingestion and the degree to which antibodies specifically adsorb onto the bacterium resulting in opsonization. The nonspecific adsorption of antibodies results in a considerable modification in the surface properties of the bacteria. Bacterial surface hydrophobicity can be altered significantly through exposure to subinhibitory concentrations of antibiotics, surfactants, lectins, etc. The effect of these changes on subsequent phagocytic ingestion is discussed.     

The effect of a range of biological polymers and synthetic surfactants on the adhesion of a marine Pseudomonas sp. strain NCMB 2021 to hydrophilic and hydrophobic surfaces

Abstract The effect of a range of biological polymers and synthetic surfactants on the adhesion of a marine Pseudomonas sp. strain NCMB2021 to hydrophilic glass and hydrophobic polystyrene has been investigated. Brij 56 (polyethylene oxide (10) cetyl ether) was the only compound that had a significant effect, almost totally inhibiting the adhesion of Pseudomonas sp. NCMB2021 to hydrophobic polystyrene, but having little or no effect on hydrophilic glass. The surfactant was demonstrated to be effective both when present in the bacterial suspension at low concentrations (approx. 5 ppm), and when pre-adsorbed onto the substratum. Brij 56 was shown to prevent the adhesion of a range of marine and fresh-water bacteria to polystyrene.
It is proposed that on a hydrophobic substratum Brij 56 is adsorbed via its hydrophobe in such a way that the polyethylene glycol chains are pointing outwards into the aqueous phase giving a surface with a high density of uncharged, highly hydrated hydrophilic chains, forming a steric barrier which inhibits the adhesion of bacteria.     

Marine antifouling laboratory bioassays: an overview of their diversity

In aquatic environments, biofouling is a natural process of colonization of submerged surfaces, either living or artificial, involving a wide range of organisms from bacteria to invertebrates. Antifouling can be defined as preventing the attachment of organisms onto surfaces. This article reviews the laboratory bioassays that have been developed for studying the control of algae and invertebrates by epibiosis (chemical ecology) and the screening of new active compounds (natural products and biocides) to inhibit settlement or adhesion, ie fouling-release coatings. The assays utilize a range of organisms (mainly marine bacteria, diatoms, algae, barnacles). The main attributes of assays for micro- and macroorganisms are described in terms of their main characteristics and depending on the biological process assessed (growth, adhesion, toxicity, behavior). The validation of bioassays is also discussed.     

肝癌细胞-胞外基质粘附性与粘附识别序列的相关性

以微管吸吮技术研究了人肝癌细胞在ＩＶ型胶原／层粘连蛋白（ＬＮ）／纤维连结蛋白（ＦＮ）裱衬表面的粘附性。进一步,用四种人工合成肽精－甘－天冬－丝（ＲＧＤＳ）、甘－精－甘－天冬－苏－脯ＧＲＧＤＴＰ）、酪－异亮－甘－丝－精（ＹＩＧＳＲ０和半胱－天冬－脯－甘－酪－异亮－甘－丝－精（ＣＤＰＧＹＩＧＳＲ）研究了肝癌细胞粘附性对两种粘附识别序列ＲＧＤ和ＹＩＧＳＲ的依赖性。为了归纳和整理实验结果,根据竞争性抑制的     

In Vitro Assessment of Nanosilver-Functionalized PMMA Bone Cement on Primary Human Mesenchymal Stem Cells and Osteoblasts

Peri-prosthetic infections caused by multidrug resistant bacteria have become a serious problem in surgery and orthopedics. The aim is to introduce biomaterials that avoid implant-related infections caused by multiresistant bacteria. The efficacy of silver nanoparticles (AgNP) against a broad spectrum of bacteria and against multiresistant pathogens has been repeatedly described. In the present study polymethylmethacrylate (PMMA) bone cement functionalized with AgNP and/or gentamicin were tested regarding their biocompatibility with bone forming cells. Therefore, influences on viability, cell number and differentiation of primary human mesenchymal stem cells (MSCs) and MSCs cultured in osteogenic differentiation media (MSC-OM) caused by the implant materials were studied. Furthermore, the growth behavior and the morphology of the cells on the testing material were observed. Finally, we examined the induction of cell stress, regarding antioxidative defense and endoplasmatic reticulum stress. We demonstrated similar cytocompatibility of PMMA loaded with AgNP compared to plain PMMA or PMMA loaded with gentamicin. There was no decrease in cell number, viability and osteogenic differentiation and no induction of cell stress for all three PMMA variants after 21 days. Addition of gentamicin to AgNP-loaded PMMA led to a slight decrease in osteogenic differentiation. Also an increase in cell stress was detectable for PMMA loaded with gentamicin and AgNP. In conclusion, supplementation of PMMA bone cement with gentamicin, AgNP, and both results in bone implants with an antibacterial potency and suitable cytocompatibility in MSCs and MSC-OM.     

钛合金和钴铬合金表面白色念珠菌粘附的研究

目的比较钛合金(Ti-6Al-4V)和钴铬合金(Chromium-Cobaltalloy)表面白色念珠菌粘附能力的大小,研究表面粗糙度与细菌粘附的关系。方法将不同表面粗糙度的钛合金和钴铬合金试件进行白色念珠菌体外粘附试验,采用菌落形成计数法测定试件表面的细菌粘附量。结果各钛合金试件组的细菌粘附量均少于相同表面粗糙度的钴铬合金试件组,两种金属试件表面的细菌粘附量均随表面粗糙度的增大而增加。结论钛合金较钴铬合金更能减少由白色念珠菌引起的义齿性口炎等并发症,同时修复体表面严格的研磨抛光也能有效减少这些并发症。