Jessica Lönn-Stensrud

Furanones, potential agents for preventing Staphylococcus epidermidis biofilm infections?

OBJECTIVES Staphylococcus epidermidis is often associated with biofilm infections related to medical implants. The aim of the present study was to find furanones that decrease biofilm formation without irritative or genotoxic effects, or effects on S. epidermidis growth. METHODS After screening including bioluminescence and biofilm assays, 2 furanones out of 11 were chosen for further studies. MIC values of the two furanones were established to determine whether biofilm inhibition effects were ascribed to inhibition of bacterial growth. To further investigate interference with communication, the effect of the furanones was tested in the presence of the autoinducer-2 precursor (S)-4,5-dihydroxy-2,3-pentanedione. The furanones were tested for possible irritative effects by the Hens egg test chorioallantoic membrane procedure. Finally, potential genotoxic effects in mice were assessed by a membrane array, and effects on global gene expression were investigated by using a microarray representing 30,000 genes of the mouse genome. RESULTS From the bioluminescence assay, 4 furanones out of 11 were chosen for further biofilm analyses. Biofilm formation by S. epidermidis was significantly decreased by the four furanones tested at concentrations not affecting microbial growth. Two furanones were chosen for further studies: one that decreased biofilm statistically more than the others and one containing two bromo substituents. The two furanones were found to be non-irritative and non-genotoxic at the concentrations used. CONCLUSIONS Furanones may inhibit biofilm formation through interference with quorum sensing and thus represent promising agents for protecting surfaces from being colonized by S. epidermidis.

A synthetic furanone potentiates the effect of disinfectants on Salmonella in biofilm

Aims:  To study a possible effect of a synthetic brominated furanone on biofilm formation and biofilm resistance to disinfectants in Salmonella enterica.

Synthesis of 5-(bromomethylene)furan-2(5H)-ones and 3-(bromomethylene)isobenzofuran-1(3H)-ones as inhibitors of microbial quorum sensing

(E)- and (Z)-5-(Bromomethylene)furan-2(5H)-ones and (E)- and (Z)-3-(bromomethylene)isobenzofuran-1(3H)-ones have been prepared starting from commercially available maleic anhydrides and phthalic anhydrides, respectively. A debrominative decarboxylation or a bromodecarboxylation reaction is a key step in the synthesis. The furanones were investigated for their ability to interfere with microbial communication and biofilm formation by Staphylococcus epidermidis.

Thiophenones inhibit Staphylococcus epidermidis biofilm formation at nontoxic concentrations

Frequent use of medical implants has led Staphylococcus epidermidis to develop into an opportunistic pathogen. The virulence is mainly linked to biofilm formation. Infections associated with biofilms are difficult to treat owing to enhanced resistance to antibiotics. Therefore, new and alternative treatments are called for. Bacterial communication is one of the regulatory mechanisms suggested to be involved in coordinating biofilm formation. In this study, we compared three communication inhibitors for preventing in vitro biofilm formation: a synthetic furanone, and two synthetic thiophenones, which are sulphur analogues of furanones. Furanones naturally source from the red macro alga Delisea pulchra. We also investigated the effect of thiophenone on transcriptional levels of genes associated with biofilm formation. We found that thiophenones were more effective in inhibiting biofilm formation than furanone, also in presence of albumin. We furthermore found that the thiophenones inhibited biofilm formation and bacterial communication more than furanones, and were less cytotoxic. The expression of the icaC and the lrgB genes, which are associated with biofilm formation, were affected by the thiophenone.

Biofilm formation on nanostructured hydroxyapatite‐coated titanium

Biofilm formation on medical devices is a common cause of implant failure, especially regarding implants that breach the epithelial tissue, so-called transcutaneous implants. Nanotechnology and the development of new nanomaterials have given the opportunity to design nanotextured implant surfaces. Such surfaces have been studied using various in vitro methods showing that nanosized features strongly benefit bone cell growth. However, little is known on how nanostructured features affect biofilm formation. The aim of this study was therefore to examine the shape- and chemical-dependent effect of a nanostructured hydroxyapatite (HA) coating on the degree of Staphylococcus epidermidis biofilm formation. Three different types of nanosized HA particles having different shapes and calcium to phosphate ratios were compared to uncoated turned titanium using safranin stain in a biofilm assay and confocal laser scanning microscopy (CLSM) for assessment of biofilm biomass and bacterial volume, respectively. No difference in biofilm biomass was detected for the various surfaces after 6 h incubation with S. epidermidis. Additionally, image analysis of CLSM Z-stacks confirmed the biofilm assay and showed similar results. In conclusion, the difference in nanomorphology and chemical composition of the surface coatings did not influence the adhesion and biofilm formation of S. epidermidis.

Thiophenone and furanone in control of Escherichia coli O103:H2 virulence

Escherichia coli are a mutual and foodborne pathogen, causing severe intestinal infections typically characterized by diarrhoea and vomiting. Biofilms are often a common source of pathogenic and nonpathogenic bacteria. Quorum sensing is a phenomenon where bacteria communicate and initiate the regulation of several virulence factors and biofilm formation. Thus, quorum sensing has been a new target in the fight against bacterial biofilms. In this study, we investigated the effect of two quorum-sensing inhibitors for preventing in vitro biofilm formation in wild-type E. coli O103:H2. Furanone F202 originates from the red algae Delisea pulchra, and thiophenone TF101 is a sulphur analogue of furanone. We also investigated the effect of thiophenone and furanone on virulence factors controlled by quorum sensing. Both TF101 and F202 interfered with biofilm formation, although TF101 was more effective. TF101 reduced motility presumably by interfering with flagella production, visualized by microscopic techniques. The expressions of flhd, which are involved in flagella synthesis, were affected by thiophenone. This is the first study exploring the effect of thiophenone on E. coli biofilm formation and virulence factors.

Effect of chemical and mechanical debridement techniques on bacterial re‐growth on rough titanium surfaces: an in vitro study

OBJECTIVE The aim of this in vitro study was to compare the effect of combined chemical and mechanical debridement of titanium (Ti) surfaces inoculated with Staphylococcus epidermidis, compared with the effect of chemical debridement alone. MATERIAL AND METHODS Different Ti surfaces were characterized with respect to roughness and subsequently inoculated with S. epidermidis. NaCl (0.9 vol.%), EDTA (12 vol.%), H₂O₂ (3 vol.%) or H₂O₂ + TiO₂ nanoparticles served as chemical debridement agents, while TiBrush was used as the mechanical debridement tool. Safranin staining assessed biomass still attached to surfaces after debridement. Biofilm viability was assessed after re-incubation of the debrided samples. SEM analysis was performed before and after the cleaning process. RESULTS Surface average roughness (Sa ) of the samples was measured at 2.22 ± 0.19 μm for group A, 0.19 ± 0.02 μm for group B, and 1.99 ± 0.10 μm for group C. When chemical debridement agents were used alone, H₂O₂-containing products were most efficient in reducing the biomass load. The surface roughness did not affect the outcome of chemical debridement. However, when combining chemical and mechanical debridement, a further reduction of biofilm load and viability was observed with best effect on the smoothest surface. CONCLUSIONS Combining H₂O₂-containing chemical agents with mechanical debridement (TiBrush) provided best reduction in biofilm mass and re-growth, when studied in vitro.

Antibacterial effect of doxycycline-coated dental abutment surfaces

Biofilm formation on dental abutment may lead to peri-implant mucositis and subsequent peri-implantitis. These cases are clinically treated with antibiotics such as doxycycline (Doxy). Here we used an electrochemical method of cathodic polarization to coat Doxy onto the outer surface of a dental abutment material. The Doxy-coated surface showed a burst release in phosphate-buffered saline during the first 24 h. However, a significant amount of Doxy remained on the surface for at least 2 weeks especially on a 5 mA-3 h sample with a higher Doxy amount, suggesting both an initial and a long-term bacteriostatic potential of the coated surface. Surface chemistry was analyzed by x-ray photoelectron spectroscopy and secondary ion mass spectrometry. Surface topography was evaluated by field emission scanning electron microscopy and blue-light profilometry. Longer polarization time from 1 h to 5 h and higher current density from 1 to 15 mA cm(-2) resulted in a higher amount of Doxy on the surface. The surface was covered by a layer of Doxy less than 100 nm without significant changes in surface topography. The antibacterial property of the Doxy-coated surface was analyzed by biofilm and planktonic growth assays using Staphylococcus epidermidis. Doxy-coated samples reduced both biofilm accumulation and planktonic growth in broth culture, and also inhibited bacterial growth on agar plates. The antibacterial effect was stronger for samples of 5 mA-3 h coated with a higher amount of Doxy compared to that of 1 mA-1 h. Accordingly, an abutment surface coated with Doxy has potential for preventing bacterial colonization when exposed to the oral cavity. Doxy-coating could be a viable way to control peri-implant mucositis and prevent its progression into peri-implantitis.

Furanones and Thiophenones in Control of Staphylococcus epidermidis Biofilm Infections

In the past decade, Staphylococcus epidermidis has emerged as one of the most frequently isolated pathogens from biofilm on implants and catheters. Since infections associated with biofilms are difficult to treat due to enhanced resistance to antibiotics, there is need of alternative approaches to prevent and to treat biofilm related infections. Quorum sensing is one of the regulatory mechanisms suggested to be involved in coordinating biofilm formation. Many studies have identified furanones as potential inhibitors of biofilm formation and quorum sensing. Here we aimed at investigating and comparing the effect of furanone and thiophenone on biofilm formation and quorum sensing. We show that both furanone and thiophenone are effective in reducing biofilm formation and bacterial communication. Thiophenones may be even more effective than furanones.

Antibacterial effect of hydrogen peroxide-titanium dioxide suspensions in the decontamination of rough titanium surfaces

Abstract The chemical decontamination of infected dental implants is essential for the successful treatment of peri-implantitis. The aim of this study was to assess the antibacterial effect of a hydrogen peroxide-titanium dioxide (H2O2–TiO2) suspension against Staphylococcus epidermidis biofilms. Titanium (Ti) coins were inoculated with a bioluminescent S. epidermidis strain for 8 h and subsequently exposed to H2O2 with and without TiO2 nanoparticles or chlorhexidine (CHX). Bacterial regrowth, bacterial load and viability after decontamination were analyzed by continuous luminescence monitoring, live/dead staining and scanning electron microscopy. Bacterial regrowth was delayed on surfaces treated with H2O2–TiO2 compared to H2O2. H2O2-based treatments resulted in a lower bacterial load compared to CHX. Few viable bacteria were found on surfaces treated with H2O2 and H2O2–TiO2, which contrasted with a uniform layer of dead bacteria for surfaces treated with CHX. H2O2–TiO2 suspensions could therefore be considered an alternative approach in the decontamination of dental implants.