The influence of patterned surface features on the accumulation of bovine synovial fluid induced aggregates of Staphylococcus aureus

Periprosthetic joint infection (PJI) after joint replacement is a major clinical issue requiring multiple surgeries and antibiotic interventions. Recent in vitro research has shown that PJI staphylococcal strains rapidly form antibiotic resistant free-floating aggregates in the presence of bovine synovial fluid (BSF). Staphylococcal aggregates are also present in human PJI joint fluid. However, the influence of surface roughness and fluid shear on the attachment and retention of such aggregates to surfaces is not known. Our aim was to assess how surface roughness and fluid shear stress influenced the attachment and retention of S. aureus BSF mediated aggregates on smooth and rough patterned titanium in flow cells compared to non-aggregated cells. S. aureus attachment of aggregates was significantly greater than single cells but was independent of surface roughness, however on the patterned surfaces aggregates preferentially accumulated in the grooves. Fibrous components in the BSF were also colocalized with the grooves. After a 24 hr attachment and incubation period different shear stresses were applied. There was significant detachment from flat surface at 1 mL/min (τw = 0.03 Pa) but minimal detachment from the patterned surfaces, even at flow rates as high as 13.9 mL/min (τw = 0.42 Pa). The retention of bacterial aggregates and biofilm by rough surfaces exposed to shear might be an important consideration of the colonization location on orthopedic implants which can have a wide range of roughness and surface features as well as influencing efficacy of shear-based debridement methods such as pulse lavage