Biofilm formation by S taphylococcus epidermidis on peritoneal dialysis catheters and the effects of extracellular products from P seudomonas aeruginosa

Biofilm formation by S taphylococcus epidermidis is a cause of infections related to peritoneal dialysis ( PD ). We have used a PD catheter flow‐cell model in combination with confocal scanning laser microscopy and atomic force microscopy to study biofilm formation by S . epidermidis . Adherence to serum‐coated catheters was four times greater than to uncoated ones, suggesting that S . epidermidis binds to serum proteins on the catheter surface. Pseudomonas aeruginosa biofilm supernatant interfered with the formation of a serum protein coat thereby reducing the capacity for biofilm formation in S . epidermidis . Supernatants from Δ pelA, Δ psl BCD and Δ rhl AB strains of P . aeruginosa showed no differences from the wild‐type supernatant indicating that the effect on serum coat formation was not due to rhamnolipids or the PelA and Psl BCD polysaccharides. Supernatant from P . aeruginosa also dispersed established S . epidermidis biofilms. Supernatants lacking PelA or Psl BCD showed no differences from the wild type but that from a Δ rhl AB strain, showed reduced, but not abolished, capacity for dispersal. This suggests that rhamnolipids are involved but not wholly responsible for the effect. Thus, supernatants from P . aeruginosa contain promising substances for the prevention and treatment of biofilm infections, although further work is required to identity more active components.