The role of mechanical properties in infections
Pseudomonas aeruginosa is an opportunistic human pathogen that forms antibiotic resistant and immune system resistant biofilms leading to chronic infections in immunocompromised patients. In Cystic Fibrosis patients, these decades-long infections evolve to produce more biofilm matrix polymers resulting in chemical benefits and unknown physical benefits. Using oscillatory bulk rheology, I measured the changing mechanical properties resulting from these evolutionary adaptations. This revealed that mechanical properties conferred to the biofilm were unique to each different matrix polymer and that during these long-term infections, retained and enhanced biofilm mechanical toughness. Enhanced toughness may aid in resistance to the immune system, therefore I created a new method to explore the limitations of neutrophil phagocytosis based on the mechanical properties of the target of engulfment. I found that mechanical properties of large, abiotic, viscoelastic targets directly influence the success of neutrophil phagocytosis and that stiffer targets with higher elastic modulus have a decreased likelihood of being successfully engulfed by neutrophils.