In the SSBB project, DCs have received extensive training on bacterial pathogens and host-pathogen interactions. They have learned about different experimental models and tools to study the pathogenesis and treatment of respiratory and intestinal tract infections, and host-pathogen interactions. Additionally, DCs were taught about different delivery modes of treatments and potential side-effects. Both academic and non-academic partners of the SSBB network contributed their expertise to the training. Several DCs have attended international conferences, where they presented their research and enhanced social skills through networking and discussions with experts in the field. DCs also actively participate in the overall management of the SSBB project.
Methods have been developed for production of non-digestible oligosaccharides, peptides, dual activity compounds and in-silico methods to evaluate synthetic antimicrobial agents. New oligosaccharides, generated using new unconventional methods, have been successfully developed. Several new peptides have been designed and synthesized, while existing peptides have been optimized. Some of these new products show enhanced efficacy in biological tests, but further testing is needed. Also, a range of oligosaccharides have been successfully linked to known antibiotics herewith creating dual-active compounds, which are currently tested for their antimicrobial activity. Computer modelling has been performed on the 3D structures of peptides, and 3D models of bacteria membranes have been developed. The new 3D models of the bacteria membrane will shed light over the peptide-bacterial membrane interactions and thus will help in the design of new peptides as well as may explain about the mechanism of action of the peptides.
Efficacy of the new compounds is being determined in high-throughput in vitro screening assays. Preliminary data indicate that the new peptides, but not the oligosaccharides, act directly as antimicrobials on three of the target bacteria. Additionally, the new compounds were assessed for their ability to enhance the efficacy of conventional antibiotics, which could lead to a reduction in antibiotic use in patients and thus herewith lowering the chance on bacteria becoming resistant as well as reducing side-effects. Besides human pathogens, also different animal pathogens were found to be highly susceptible to the newly developed peptides, making these compounds applicable for the veterinary field. Knowledge of biosafety and off-target effects of our new antimicrobials is essential for application in humans and animals. Initial studies showed that none of the compounds induced cytotoxicity. Assessment of off-target effects, by investigating effects on microbiota in lungs and gut, indicated that some of these bacteria were highly susceptible, while others were highly resistant to the tested peptides. These findings, as well as impact on infection-induced immunity, will be further evaluated in vivo experimental models. To enable non-invasive imaging of pathogens, light emitting Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus have been established. These bacteria are currently being tested before use in vitro and in vivo.
Well-defined in vitro models have been established to simulate the gut and lung mucosal epithelium. These models will be used to test effects of antimicrobials on bacterial infections as well as to assess the impact on the host epithelial barrier and immune function. Initial studies in 3D primary bronchial organoids verified that peptides at concentrations that showed synergistic effects with standard antibiotics, are non-cytotoxic. Transcriptomic analyses will be performed to further understand the cellular response to these compounds, ensuring safety and efficacy in therapeutic applications. Also, different in vivo preclinical animal models to study treatment of bacterial infections and potential off-target effects have been developed. Lastly, in vitro models to study formation of biofilms, a process with which bacteria shield themself from antibiotics and from host immunity, have been successfully developed. Peptides showed promising results in inhibiting biofilm formation by P. aeruginosa and S. aureus. Additionally, coating of implantable substrates with peptides yielded promising results on preventing biofilm formation on medical implants. Our data suggest that the combination of implantable substrates with peptides could lower the dependency on systemic antibiotics and improve the lifespan of medical implants.
