The Bacteria at Surfaces group focuses on understanding, predicting and controlling material-bacteria interactions for health-related applications. Especially, we combine interdisciplinary knowledge in the pursuit of understanding how bacteria adhere to surfaces, and how the adhesion can be controlled. Among our core strengths are the broad expertise, ranging from microbiology to biomaterials, and the long-term experience in working with hospital and industry and finding solutions to biofilm problems.

The key research aspects of the Bacteria at Surfaces group include:

• Studying basic mechanisms of bacterial adhesion on surfaces

• Developing antibacterial and anti-adhesive surfaces to prevent/reduce biofilm formation

• Designing new approaches to sense/treat antimicrobial resistance

• Studying mechanisms of biofilm resistance toward antimicrobials

Many models have been developed to study biofilms including simple in vitro and complex in vivo ones. Even though these models have progressively provided knowledge and information on biofilm formation, we are still far from a complete understanding on how various factors influence the interactions between the biofilms and medical devices. The Bacteria at Surfaces group is interested in the development and improvement of clinically relevant in vitro biofilm models under specific in vivo conditions such as flow rate, nutrient content, mixed biofilm, and co-existence of human and bacterial cells, aiming for more reliable assessment of antimicrobial surfaces.

Biofilm on ex vivo ureteral stent complexity of the in vivo biofilm

Upon sensing and interacting with surfaces, bacteria trigger a variety of changes in gene expression, including the genes essential for cell-cell communication, motility and surface attachment. Although changes in these phenotypes have been observed, the mechanisms used by bacterial cells for sensing and responding to surfaces are still not well understood. To develop novel classes of materials that inhibit or reduce bacterial adhesion or proliferation, a better understanding of these mechanisms is necessary. The Bacteria at Surfaces group is interested in studying the underlining mechanisms of surface sensing at the molecular level and the consequent impact on cell adhesion.

Fig. 2. Scanning electron microscopy (SEM) image of a ureteral stent surface covered with a dense mass of crystalline biofilm.

The majority of infections are caused by bacterial biofilms. Bacteria living in biofilms can tolerate much higher antibiotic concentrations compared to planktonic bacteria and survive long enough to evolve antimicrobial resistance (AMR). Our group aims to investigate how bacteria generate resistant during biofilm formation on surfaces coated with antimicrobials at the molecular level. Understanding the contribution of biofilms to AMR acquisition and spread will lead to the development of novel antimicrobial strategies to prevent biofilm-associated infection and AMR.

Understanding mechanism of biofilm resistance toward antimicrobial surfaces by identifying involved genes and pathways.

The Bacteria at Surfaces group works with different bacterial strains such as Gram negative and Gram positive species, multi-resistant pathogens, biosafety level I and II bacterial species.

We study biofilms in microtiter plates, flow chambers, as well as in bioreactor systems under static or dynamic conditions. Bacterial adhesion and biofilms on surfaces are analyzed by different methods such as Crystal violet assays, Fluorescence assays, Microscopy (CLSM, SEM), Real-time quantitative PCR.

• Collaboration with Hospital St. Gallen (2015-2016): Biofilms on ureteral stents - Development of an in vitro simulation model towards exploring novel stent surfaces and materials
• CTI project (2015-2017): Metal-ion doped TiN layers to reduce hospital acquired infections
• CTI project (2014-2016): Endodontic cleaning and disinfection solution
• CTI project (2014-2016): Development of novel non-biocidal textile coatings reducing sweat odor accumulation
• CTI project (2014-2015): Biofilm removal from and effective cleaning of medical devices by means of innovative enzymatic detergents
• CTI project (2011-2013): Development of novel non-biocidal textile coatings reducing bacterial adhesion