Incorporation of collagen into bacterial biofilms impedes phagocytosis by neutrophils

Biofilms are communities of microbes embedded in a matrix of extracellular polymeric substances (EPS). EPS can be produced by biofilm organisms and can also originate from the host. The biofilm matrix protects bacteria from clearance by the immune system, and some of that protection likely arises from the mechanical properties of the biofilm. It has been shown that collagen, a host-produced protein abundant in many infection sites, can be incorporated into biofilms and change biofilm mechanics. Here we use two biofilm-forming human pathogens, Pseudomonas aeruginosa and Staphylococcus aureus, to study the role of incorporated collagen in the immune clearance of biofilms by human neutrophils. We also investigate the effects of enzymatic breakdown of host-derived materials on biofilm mechanics and susceptibility to host immune clearance. Microrheology, SEM and reflectance confocal microscopy can characterize how incorporated collagen affects biofilm microstructures and mechanical properties.