Biofilm-stimulated epithelium modulates the inflammatory responses in co-cultured immune cells

The gingival epithelium is a physical and immunological barrier to the microbiota of the oral cavity, which interact through soluble mediators with the immune cells that patrol the tissue at the gingival epithelium. We sought to develop a three-dimensional gingivae-biofilm interface model using a commercially available gingival epithelium to study the tissue inflammatory response to oral biofilms associated with “health”, “gingivitis” and “periodontitis”. These biofilms were developed by sequential addition of microorganisms to mimic the formation of supra- and sub-gingival plaque in vivo. Secondly, to mimic the interactions between gingival epithelium and immune cells in vivo, we integrated peripheral blood mononuclear cells and CD14+ monocytes into our three-dimensional model and were able to assess the inflammatory response in the immune cells cultured with and without gingival epithelium. We describe a differential inflammatory response in immune cells cultured with epithelial tissue, and more so following incubation with epithelium stimulated by “gingivitis-associated” biofilm. These results suggest that gingival epithelium-derived soluble mediators may control the inflammatory status of immune cells in vitro, and therefore targeting of the epithelial response may offer novel therapies. This multi-cellular interface model, both of microbial and host origin, offers a robust in vitro platform to investigate host-pathogens at the epithelial surface

Biodiversity, community structure and function of biofilms in stream ecosystems

Multi-species, surface-attached biofilms often dominate microbial life in streams and rivers, where they contribute substantially to biogeochemical processes. The microbial diversity of natural biofilms is huge, and may have important implications for the functioning of aquatic environments and the ecosystem services they provide. Yet the causes and consequences of biofilm biodiversity remain insufficiently understood. This review aims to give an overview of current knowledge on the distribution of stream biofilm biodiversity, the mechanisms generating biodiversity patterns and the relationship between biofilm biodiversity and ecosystem functioning

Synergistic Activity of Fosfomycin, Ciprofloxacin, and Gentamicin Against Escherichia coli and Pseudomonas aeruginosa Biofilms

Gram-negative (GN) rods cause about 10% periprosthetic joint infection (PJI) and represent an increasing challenge due to emergence of antimicrobial resistance. Escherichia coli and Pseudomonas aeruginosa are among the most common cause of GN-PJI and ciprofloxacin is the first-line antibiotic. Due to emergence of fluoroquinolone resistance, we evaluated in vitro the activity of fosfomycin, ciprofloxacin, and gentamicin, alone and in combinations, against E. coli and P. aeruginosa biofilms. Conventional microbiological tests and isothermal microcalorimetry were applied to investigate the anti-biofilm activity of the selected antibiotics against standard laboratory strains as well as clinical strains isolated from patients with prosthetic joint associated infections. The biofilm susceptibility to each antibiotic varied widely among strains, while fosfomycin presented a poor anti-biofilm activity against P. aeruginosa. Synergism of two-pair antibiotic combinations was observed against different clinical strains from both species. Highest synergism was found for the fosfomycin/gentamicin combination against the biofilm of E. coli strains (75%), including a gentamicin-resistant but fosfomycin-susceptible strain, whereas the gentamicin/ciprofloxacin combination presented synergism with higher frequency against the biofilm of P. aeruginosa strains (71.4%). A hypothetical bacteriolysis effect of gentamicin could explain why combinations with this antibiotic seem to be particularly effective. Still, the underlying mechanism of the synergistic effect on biofilms is unknown. In conclusion, combinatorial antibiotic application has shown to be more effective against biofilms compared to monotherapy. Further in vivo and clinical studies are essential to define the potential treatment regimen based on our results

A keystone Methylobacterium strain in biofilm formation in drinking water

The structure of biofilms in drinking water systems is influenced by the interplay between biological and physical processes. Bacterial aggregates in bulk fluid are important in seeding biofilm formation on surfaces. In simple pure and co-cultures, certain bacteria, including Methylobacterium, are implicated in the formation of aggregates. However, it is unclear whether they help to form aggregates in complex mixed bacterial communities. Furthermore, different flow regimes could affect the formation and destination of aggregates. In this study, real drinking water mixed microbial communities were inoculated with the Methylobacterium strain DSM 18358. The propensity of Methylobacterium to promote aggregation was monitored under both stagnant and flow conditions. Under stagnant conditions, Methylobacterium enhanced bacterial aggregation even when it was inoculated in drinking water at 1% relative abundance. Laminar and turbulent flows were developed in a rotating annular reactor. Methylobacterium was found to promote a higher degree of aggregation in turbulent than laminar flow. Finally, fluorescence in situ hybridisation images revealed that Methylobacterium aggregates had distinct spatial structures under the different flow conditions. Overall, Methylobacterium was found to be a key strain in the formation of aggregates in bulk water and subsequently in the formation of biofilms on surfaces

Sessile Legionella pneumophila is able to grow on surfaces and generate structured monospecies biofilms

Currently, models for studying Legionella pneumophila biofilm formation rely on multi-species biofilms with low reproducibility or on growth in rich medium, where planktonic growth is unavoidable. The present study describes a new medium adapted to the growth of L. pneumophila monospecies biofilms in vitro. A microplate model was used to test several media. After incubation for 6 days in a specific biofilm broth not supporting planktonic growth, biofilms consisted of 5.36 ± 0.40 log (cfu cm−2) or 5.34 ± 0.33 log (gu cm−2). The adhered population remained stable for up to 3 weeks after initial inoculation. In situ confocal microscope observations revealed a typical biofilm structure, comprising cell clusters ranging up to 300 μm in height. This model is adapted to growing monospecies L. pneumophila biofilms that are structurally different from biofilms formed in a rich medium. High reproducibility and the absence of other microbial species make this model useful for studying genes involved in biofilm formation

A comparison of the antimicrobial efficacy of silver diamine fluoride and silver nitrate: an in vitro study

A COMPARISON OF THE ANTIMICROBIAL EFFICACY OF SILVER DIAMINE FLUORIDE AND SILVER NITRATE: AN IN VITRO STUDY By: Nicholas L Luke, D.D.S. A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Dentistry at Virginia Commonwealth University. Virginia Commonwealth University, May 2018 Thesis Advisor: William O. Dahlke Jr., D.M.D. Pediatric Dentistry, Department Chair Purpose: To determine the antimicrobial efficacy of SDF and SN/NaF. Methods: Three bacterial species were combined to create an in vitro biofilm. Treatment was completed with SN, SN/NaF, SDF, SDF½ or untreated (control). Results: The untreated group demonstrated significantly higher growth than all other treatment groups across the study. On the BHI-plates (1-day), there were significant differences between all treatments except SDF and SDF½. On the BHI-plates (3-days), SN/NaF was not significantly different from SDF or SDF½. On the L-MRS-plates (1-day), both SN treatment groups yielded significantly higher growth than the SDF groups. On the L-MRS-plates (3-days), SN yielded significantly higher growth than SN/NaF, SDF, and SDF½. Conclusion: SDF is more effective than SN/NaF, with the exception of BHI-plates (3-days) only and SN/NaF is more effective than SN on primarily S. mutans and L. acidophilus. There is evidence of a possible antimicrobial tolerance of oral bacteria to silver

Catalysis of the electrochemical reduction of oxygen by bacteria isolated from electro-active biofilms formed in seawater

Biofilmsformed in aerobic seawater on stainless steel are known to be efficient catalysts of the electrochemicalreduction of oxygen. Based on their genomic analysis, seven bacterial isolates were selected and a cyclic voltammetry (CV) procedure was implemented to check their electrocatalytic activity towards oxygenreduction. All isolates exhibited close catalytic characteristics. Comparison between CVs recorded with glassy carbon and pyrolytic graphite electrodes showed that the catalytic effect was not correlated with the surface area covered by the cells. The low catalytic effect obtained with filtered isolates indicated the involvement of released redox compounds, which was confirmed by CVs performed with adsorbed iron–porphyrin. None of the isolates were able to form electro-activebiofilms under constant polarization. The capacity to catalyze oxygenreduction is shown to be a widespread property among bacteria, but the property detected by CV does not necessarily confer the ability to achieve stable oxygenreduction under constant polarization

Autogenic versus environmental control during development of river biofilm

In the natural environment, microbial community structure of river biofilm is controlled by biotic and abiotic factors. This study explored the capacity to manipulate the structure of microbial communities by modifying environmental conditions during the course of biofilm development. River epilithic biofilm was cultivated in situ on artificial substrates placed parallel to river water flow. Substrates were incubated for 3 and 5.5 weeks in river to allow natural biofilm development, at two sites with contrasting physico-chemical characteristics. The first site (Aurade´ , Gers, France) was located in an agricultural watershed basin and the second site (Larroque, Haute-Garonne, France) was located in a forested watershed basin. After 3 weeks of biofilm development, a subset of substrates was collected from one site and transplanted to the second site where they remained for 2.5 further weeks. Epilithic bacterial community structure (at 3 weeks from each site and at 5.5 weeks from biofilms with and without transplantation) was assessed using PCR-DGGE of 16S rDNA fragment. Biofilm biomass was estimated using ash free dry mass (AFDM). After 3 weeks of development, biofilms from the two sites exhibited comparable AFDM values (average of 1.4¡0.2 g.mx2). A difference between the two sites was observed after 5.5 weeks of development: AFDM decreased for biofilms from the agricultural watershed basin (from 1.4 to 0.18 g.mx2) as a consequence of grazing pressure (Bithynia), and increased for biofilms from the forested agricultural watershed (from 1.4 to 2.6 g.mx2). Microbial community analyses revealed a differentiated community structure between biofilms from the different sites and exhibited a change of microbial community structure after 5.5 weeks of biofilm development. These observations confirm a process of ecological succession in microbial communities. Changing the incubation site during biofilm development modified the trajectory of these ecological successions, suggesting that site characteristics mainly conditioned the structure of these microbial communities