Fibronectin (Fn) is recognized for its ability to mediate Staphylococcus aureus (SA) adhesion. The number of Fn receptors is dependent on the phase of growth, and type of media. Furthermore, it was of interest to examine SA and Staphylococcus epidermidis (SE) adherence to porcine Fn (IBF 10 ng/ml) immobilized on tissue culture plates. The aim of our study was to examine if removal of FN receptors by growing bacteria in an antibiotic containing medium decreased the ability to adhere and of pefloxacin (P) anti-adhesive properties were medium dependent. As SE usually lack Fn binding capabilities, it seemed of interest to investigate if the effects of subinhibitory concentrations of P were modified by medium or Fn. We found: a) For SA: whether Fn coated onto plastic substrata promoted adherence of strains, P's anti-adhesive properties were saved, non medium or phase of growth dependent. b) For SE: adherence properties were decreased if Fn was coated onto plates. P's anti-adhesive properties were not modified and non medium dependent. The number of Fn receptors on clinical isolates of SA correlates with the invasiveness of the isolates. As P reduced the binding of SA to Fn coated plates, this observation may have important implications for antimicrobial prophylaxis.