Antibiotic activity against Staphylococcus epidermidis biofilms in dialysis fluids

Infection associated with medical devices may be resistant to conventional antibiotic therapy. A potential mechanism explaining this variable therapeutic response is the presence of bacterial biofilms on the surface of the prosthetic material which may confer a biologically important protective function to the entrapped bacteria. To study these questions, we prepared standardized biofilms and conventional fluid phase cultures from a panel of ten Staphylococcus epidermidis strains. All ten strains showed in the fluid phase a variable pattern of sensitivity to seven antibiotics but were uniformly sensitive to rifampin and vancomycin. In the biofilm phase they demonstrated solid antibiotic resistance with the variable exception of rifampin. The nature of the milieu was a major variable. Fresh peritoneal dialysis solution enhanced the activity of rifampin but this effect was not present with spent or neutral dialysis fluids.