Colony-formation of staphylococci in fibronectin-soft-agar

Colony-formation of 50 staphylococcal cultures was examined in fibronectin-, fibrinogen- and serum-soft-agar and compared with the respective fibronectin- and fibrinogen-clumping-reactions. Forty-two of the 50 cultures formed compact colonies in fibronectin-soft-agar undistinguishable from those in fibrinogen- or serum-soft-agar and gave distinct clumping-reactions with fibronectin and fibrinogen. The remaining 8 cultures (7 Staphylococcus aureus and 1 Staphylococcus epidermidis ATCC 14990) grew diffusely and gave no clumping-reactions with fibronectin or fibrinogen. Thus, fibronectin could elicit compact colony-formation of the staphylococci.