Initial Adhesion Of Bacteria Research Articles

A Surface-Active Agent from Saccharomyces cerevisiae Influences Staphylococcal Adhesion and Biofilm Development

Bacterial biofilms which are responsible for a number of diseases are very difficult to control effectively because of their high resistance to antibiotics and the host defence system. The use of natural products decreasing or preventing initial adhesion of bacteria and biofilm formation is one of the alternative therapeutic strategies taken into consideration. We ask the question, whether a crude extract from the cell wall of Saccharomyces cerevisiae (mannoprotein), which possesses surfactant activity, may be used as inhibitor of Staphylococcus aureus and S. epidermidis biofilm development. By using the "bactericidal spot assay" it was demonstrated that mannoprotein had no direct antibiotic activity against the tested strains. The influence of this extract on initial adhesion, biofilm formation and dispersal of preformed biofilms was studied using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) reduction assay. In this assay, live bacteria with an active electron transport system reduce the tetrazolium salt to a water-soluble purple formazan product, and optical density reading (A550) values are directly dependent on their cell numbers. Yeast-derived surfactant, when adsorbed in the microplate wells or present in the medium, was effective both in decreasing the initial deposition of staphylococci and in reducing the amount of growing biofilm, quantitated after 24 h of co-incubation with the bacteria. It also changed the parameters of biofilm morphology analyzed by PHLIP - the confocal laser scanning microscopy image quantification package. Mannoprotein also accelerated the detachment of mature staphylococcal biofilms, preformed in optimal conditions. It was concluded that mannoprotein anti-biofilm action reflects its influence on cell surface hydrophobicity.

Antibacterial and osteogenic properties of silver‐containing hydroxyapatite coatings produced using a sol gel process

Since bacterial infection is a rising complication following the wide use of implant, there is considerable attention on the effect of implant surface properties on bacterial adhesion. In this study, the effect of silver (Ag) doped hydroxyapatite (HA) coatings on initial antibacterial adhesion and osteoblast cell proliferation and differentiation was investigated. Using a sol-gel process, HA coatings doped with 1 wt % AgNO(3) (AgHA1.0) and 1.5 wt % Ag (AgHA1.5) were prepared. Coated surfaces were characterized using X-ray diffraction (XRD) and contact angles measurements. The initial bacteria adhesion was evaluated using a RP12 strain of Staphylococcus epidermidis (ATCC 35984) and the Cowan I strain of Staphylococcus aureus, whereas osteoblast proliferation and differentiation were evaluated using human embryonic palatal mesenchyme cells (HEPM), an osteoblast precursor cell line. In this study, XRD analysis of all surfaces indicated peaks corresponding to HA. Contact angles for AgHA surfaces were observed to be significantly lower when compared to HA surfaces. In vitro initial bacterial adhesion study indicated a significantly reduced number of S. epidermidis and S. aureus on AgHA surfaces when compared to HA surface. The use of HEPM cells indicated no significant difference in double-stranded DNA (dsDNA) production between all surfaces. Additionally, no differences in alkaline phosphatase specific activity were observed between HA and AgHA1.0 surfaces. Overall, it was concluded that AgHA1.0 has the similar biological activity as HA, with respect to bone cell proliferation and differentiation. In addition, the AgHA1.0 was also concluded to have the ability to minimize the initial bacteria adhesion. (c) 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2007.

N-acetyl-L-cysteine affects growth, extracellular polysaccharide production, and bacterial biofilm formation on solid surfaces.

N-Acetyl-L-cysteine (NAC) is used in medical treatment of patients with chronic bronchitis. The positive effects of NAC treatment have primarily been attributed to the mucus-dissolving properties of NAC, as well as its ability to decrease biofilm formation, which reduces bacterial infections. Our results suggest that NAC also may be an interesting candidate for use as an agent to reduce and prevent biofilm formation on stainless steel surfaces in environments typical of paper mill plants. Using 10 different bacterial strains isolated from a paper mill, we found that the mode of action of NAC is chemical, as well as biological, in the case of bacterial adhesion to stainless steel surfaces. The initial adhesion of bacteria is dependent on the wettability of the substratum. NAC was shown to bind to stainless steel, increasing the wettability of the surface. Moreover, NAC decreased bacterial adhesion and even detached bacteria that were adhering to stainless steel surfaces. Growth of various bacteria, as monocultures or in a multispecies community, was inhibited at different concentrations of NAC. We also found that there was no detectable degradation of extracellular polysaccharides (EPS) by NAC, indicating that NAC reduced the production of EPS, in most bacteria tested, even at concentrations at which growth was not affected. Altogether, the presence of NAC changes the texture of the biofilm formed and makes NAC an interesting candidate for use as a general inhibitor of formation of bacterial biofilms on stainless steel surfaces.

The effects of urine and temperature on the physicochemical surface properties and adhesion behaviour of uropathogenic bacteria

Bacterial adhesion in relation to urinary-tract infections has gained importance in the last years because of the increasing catheterization in hospitals to assist post-surgery flow of urine. Since the initial adhesion of bacteria to biomaterials is governed by physicochemical forces emerging from the physicochemical properties of both interacting phases, we have investigated the physicochemical surface changes of uropathogen Enterococcus faecalis ATCC29212 bacteria due to the presence of urine in its growth medium and to the differences in the environmental temperature. Urine-grown cells were found to be less hydrophobic based on water contact angles at 22°C, while no changes were detected at 37°C. In addition, they exhibited higher acid-base surface energy component than urine-free cultured cells. These changes in surface properties were also reflected in thermodynamic predictions of the adhesion to glass and silicone, which were experimentally compared with the in vitro adhesion curves obtained in a parallel plate flow chamber. The shapes of the adhesion graphs indicated that interaction free energies should be used to describe only the initial adhesion stages. Adhesion to silicone was always enhanced by urine-grown cells, while the adhesion to glass did not seem to be affected by the urine constituents. Despite the fact that the interaction free energies were not able to explain the adhesion process in some cases, changes in the electron-donor and electron-acceptor parameters of their surface free energy due to urine addition seemed to have a relation with initial adhesion rates.

Comparison of bacterial and tissue cell initial adhesion on hydrophilic/hydrophobic biomaterials

In this study, interactions of widely-used polymeric biomaterials, i.e. poly(hydroxyethyl methacrylate) (PHEMA) and its copolymer with dimethylaminoethyl methacrylate (PHEMA-20% DMAEMA), polyurethane (PU), polypropylene (PP), poly(vinyl chloride) (PVC), and poly(lactideglycolide) (PLGA), with three pathogenic bacteria and one nonpathogen were investigated comparatively with the adhesion of two tissue cells in different morphologies, i.e. fibroblast-like baby hamster kidney (BHK 21) cells and epithelial Madine Darby kidney (MDBK) cells. Biomaterials were prepared in the membrane form by bulk polymerization or solvent casting. Surface characterization studies showed that these polymers have different surface free energies in the range of 26.9-63.1 ergcm-2 and they have smooth surfaces. The bacteria used were; Escherichia coli ATCC 25922, Staphylococcus epidermidis ATCC 12228, Staphylococcus aureus, and Lactobacillus acidophilus B-13. Initial adhesion of bacteria to the polymeric surfaces was examined under static conditions and in a laminar flow cell. The adhesion behaviour of S.aureus and S.epidermidis was found independent of the polymeric surface hydrophobicity. However, the percentage of attached E. coli decreased when increasing the surface free energy of the polymer, while L. acidophilus showed just the opposite behaviour. The comparative results indicated that the adhesion of BHK and MDBK cell was lowest on the most hydrophilic PHEMA surface and highest on the most hydrophobic PP surface. In contrast to the case of bacterial adhesion, no relationship was found between polymer hydrophobicity and mammalian cell adherence.

Complex regulatory network controls initial adhesion and biofilm formation in Escherichia coli via regulation of the csgD gene.

The Escherichia coli OmpR/EnvZ two-component regulatory system, which senses environmental osmolarity, also regulates biofilm formation. Up mutations in the ompR gene, such as the ompR234 mutation, stimulate laboratory strains of E. coli to grow as a biofilm community rather than in a planktonic state. In this report, we show that the OmpR234 protein promotes biofilm formation by binding the csgD promoter region and stimulating its transcription. The csgD gene encodes the transcription regulator CsgD, which in turn activates transcription of the csgBA operon encoding curli, extracellular structures involved in bacterial adhesion. Consistent with the role of the ompR gene as part of an osmolarity-sensing regulatory system, we also show that the formation of biofilm by E. coli is inhibited by increasing osmolarity in the growth medium. The ompR234 mutation counteracts adhesion inhibition by high medium osmolarity; we provide evidence that the ompR234 mutation promotes biofilm formation by strongly increasing the initial adhesion of bacteria to an abiotic surface. This increase in initial adhesion is stationary phase dependent, but it is negatively regulated by the stationary-phase-specific sigma factor RpoS. We propose that this negative regulation takes place via rpoS-dependent transcription of the transcription regulator cpxR; cpxR-mediated repression of csgB and csgD promoters is also triggered by osmolarity and by curli overproduction, in a feedback regulation loop.

The Role of Exopolymers Produced by Sphingomonas paucimobilis in Biofilm Formation and Composition

Exopolymers have been associated with the initial adhesion of bacteria, which is the primary step for biofilm formation. Moreover, the polymeric matrix of biofilms has a considerable influence on some of the most important physical and physiological properties of biofilms. The role of extracellular polymers in biofilm formation was studied using three mutants of Sphingomonas paucimobilis with increasing capabilities for exopolymer production. The physical, biochemical and physiological properties of three different layers of each biofilm were determined. The layers were detached by submitting the biofilm to increasing shear stress. The results revealed that the presence of exopolymers in the growth medium was essential for biofilm formation. The mutant producing the highest amount of exopolymer formed very thick biofilms, while the biofilms formed by the medium exopolymer producer were on average 8 times thinner. The lowest exopolymer producer did not form biofilm. In both types of biofilms, exopolymer density increased with depth, although this tendency was more significant in thinner biofilms. Cell distribution was also more heterogeneous in thinner biofilms, exhibiting a greater accumulation of cells in the inner layers. The thicker biofilms had very low activity in the inner layer. This was related to a high accumulation of proteins and DNA in this layer due to cell lysis and hydrolytic activity. Activity in the thin biofilm was constant throughout its depth, suggesting that there was no nutrient limitation. The production of exopolymers by each cell was constant throughout the depth of the biofilms, although it was greater in the case of the higher producer.

Effects of substratum wettability and molecular topography on the initial adhesion of bacteria to chemically defined substrataa b

Self‐assembled monolayers (SAMs) constructed from alkanethiols, whose surface composition and wettability can be rigorously characterized, were used to investigate bacterial adhesion to surfaces. Mixtures of methyl‐terminated and hydroxyl‐terminated alkanethiols were used to produce a series of SAMs with different wettabilities for water and hexadecane. Also, mixtures of 11‐carbon and 18‐carbon SAMs were used to determine the influence of molecular topography on bacterial adhesion and surface wettability. In particular, attachment to mixed chain‐length SAMs in which hydroxyl‐terminated, 11‐carbon alkanethiols were mixed with methyl‐terminated, 18‐carbon alkanethiols was evaluated, to determine whether masking of the polar hydroxyl groups by the longer alkane chains affected bacterial attachment to these surfaces. Substratum wettability was evaluated by measuring the contact angles of water and hexadecane. The kinetics of attachment of an estuarine pseudomonad (MI‐1A) to these surfaces in a laminar flow chamber were measured over periods of 120 min. The numbers of cells attached after 120 min and the percentages of attached cells that adsorbed or desorbed between successive measurements were quantified by phase‐contrast microscopy and digital image processing. SAMs exhibited various substratum compositions and wettabilities, ranging from hydrophilic (contact angle of water ≤ 10°), hydroxyl‐terminated monolayers to hydrophobic (contact angle of water > 100°), methyl‐terminated monolayers. With both types of mixed‐SAMs, the greatest numbers of attached cells occurred on hydrophobic surfaces (∼4.5 x 104 cells mm‐2). In addition, the desorption of cells between successive measurements (ca 2 min) decreased with increasing substratum hydrophobicity. The relationship between substratum wettability and adhesion was also influenced by substratum topography. There were greater numbers of attached cells and less desorption with the SAMs composed of nonpolar polymethylene chains overlying a plane of hydroxyl groups than with SAMs composed of hydroxyl‐ and methyl‐terminated alkanethiols with equal chain‐lengths. This study indicates that not only bulk surface chemistry, but also molecular topography, influence bacterial adhesion.

Adhesion and Growth of Thermoresistant Streptococci on Stainless Steel during Heat Treatment of Milk

Streptococcus thermophilus adheres to plates of cheese-milk pasteurizers during the operating time. The adherence of these bacteria in the regenerator section of the heat exchanger is much larger than in the heating section. Calcium phosphate deposits are higher in the heating section than in the regenerator section. In a series of laboratory experiments with batch cultures of S. thermophilus B, adherence of this organism on stainless steel was determined after growth in the milk was nearly completed. It was found that S. thermophilus B adhered equally well to stainless steel in raw as in pasteurized milk cultures. Pre-coating of stainless steel with calcium phosphate reduced bacterial adhesion maximally by only 50%. It was shown that initiation of growth of S. thermophilus B was delayed in raw milk and not in pasteurized milk. The experimental set-up was thereafter changed in such a way that either raw or pasteurized milk containing high numbers of viable S. thermophilus B streamed in a continuous flow along stainless steel. In this way a better simulation of the practical situation could be achieved. Now the initial adhesion of bacteria to stainless steel along which raw or pasteurized milk passed was approximately the same. During longer operating times, however, the population of bacteria on the steel in pasteurized milk increased much faster than on steel in raw milk. After 4 h of operating time stainless steel test plates contained 1.0 × 107 and 7.0 × 105 cfu/cm2, respectively. It is suggested that raw milk contains growth-inhibiting compound(s), and by continuous feed of raw milk the effect of the inhibiting compound(s) is substantially increased. This results in a slow increase of the bacterial number on the surface. When pasteurized milk streams along the plates, bacterial growth is not inhibited, resulting in a fast increase.

The hydrophobicity of bacteria - an important factor in their initial adhesion at the air-water interface.

Bacteria isolated from the surface and the subsurface water at four stations along the Swedish west coast were assessed for their hydrophobicity with hydrophobic interaction chromatography (HIC). The surface bacteria were sampled by the Teflon sheet technique. [3H]-L-leucine metabolically labeled isolates were run on a column packed with Octyl-Sepharose CL-4B gel. The relative hydrophobicity of the bacteria was expressed as the ratio, g/e, between the radioactivity of the gel and the eluate. The results revealed a positive correlation between the degree of enrichment of bacteria at the surface and their hydrophobicity. The subsurface bacteria exhibited a broader spectrum of g/e-values than the surface bacteria. The initial adhesion of bacteria to the surface microlayer depends on several factors of which the hydrophobic interaction may be one of the most important.