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PhD ceremony Mr. S. Daghighi: Bio-optical imaging of host-bacteria interactions in biomaterial-associated infection

When:We 18-12-2013 at 11:00
Where:Academiegebouw, Broerstraat 5, Groningen

PhD ceremony: Mr. S. Daghighi

Dissertation: Bio-optical imaging of host-bacteria interactions in biomaterial-associated infection

Promotor(s): prof. H.J. Busscher, prof. H.C. van der Mei

Faculty: Medical Sciences

The first aim of this thesis is to gain a better understanding of the host immune system interaction with bacteria in a biomaterials-associated infection (BAI). Furthermore, we want to develop an in vivo implant BAI models based on bioluminescence and fluorescence imaging.

We discuss a number of hypotheses to explain the decreased infection risk associated with the use of degradable versus non-degradable biomaterials. In a murine model we compared staphylococcal persistence on and around a degradable and non-degradable surgical mesh. Bioluminescent staphylococci persisted on and around non-degradable meshes up to the 28th day, whereas the bacteria disappeared from surrounding tissues once a degradable mesh had fully dissolved. Bioluminescent flux from S. aureus Xen29 was quantified in absence and presence of different antibiotics. Staphylococcal bioluminescence at sub-inhibitory concentrations seemed to be enhanced when measured 24 h after incubation. Therefore, antibiotic pressure may impact the relationship between bacterial numbers and their bioluminescence. We investigated the relationship between MMP- and integrin-expression and the clearance of infecting S. aureus around implanted biomaterials in a murine model. MMP- and integrin-expression were equally enhanced in presence of staphylococci or biomaterials up to 7 days post-implantation, but bacterial clearance was higher in absence of biomaterials. MMP- and integrin-expression were enhanced in presence of staphylococci and biomaterial, but the immune system remained hampered in eradicating bacteria during the first 7 days post-implantation. Finally, different subjects of our findings are discussed.