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Recently, livestock-associated Methicillin-resistant Staphylococcus aureus (LA-MRSA) mostly belonging to the clonal complex (CC) 398 -were recognized as a source for human infections with a potential for a major healthcare challenge, yet, the pathogenic mechanism of endemic LA-MRSA and of their Methicillin-susceptible counterparts (LA-MSSA) for species barriers transmission, colonization, and disease formation are largely unknown. Crucial steps towards disease include bacterial adhesion to host cell matrix components, invasion of cells and tissues, and evasion from host immune response. We are addressing these processes by analyzing the ability of epidemiologically relevant zoonotic and non-zoonotic MRSA and MSSA to adhere to human and animal cell matrix components that are known to be important for bacterial adhesion. In a second approach, the uptake of zoonotic and non zoonotic MRSA and MSSA by human and porcine blood phagocytes is investigated.
Our preliminary results suggest that CC398 isolates obtained from animal sources possessed reduced adhesion capacities to human and bovine fibronectin, respectively, if compared to CC398 isolates obtained from human, and to Hospital acquired-and community acquired MRSA. Strain-specific variations in adhesion identified by the ELIZA-based adhesion assay correlated with adhesion force measurements determined by Atomic Force Microscopy (AFM). In our whole blood phagocytosis assays, we surprisingly observed significant differences in the bacterial uptake by porcine and human blood granulocytes, but no such differences in terms of the origin of the isolates.