LACK OF THE EXTRACELLULAR 19-KILODALTON FIBRINOGEN-BINDING PROTEIN FROM STAPHYLOCOCCUS-AUREUS DECREASES VIRULENCE IN EXPERIMENTAL WOUND-INFECTION

A mutant deficient for the 19-kDa extracellular fibrinogen-binding pro tein (Fib) from Staphylococcus aureus has been constructed, The gene w as inactivated by allele replacement. A 2.0-kb fragment from transposo n Tn4001 carrying the gene for gentamicin resistance was inserted into the gene encoding Fib (fib). The genotype was verified by PCR analysi s, and the loss of Fib was demonstrated by Western blotting (immunoblo tting), The mutation has not altered the ability of the strain to bind to fibrinogen or fibronectin compared with that of the isogenic paren tal strain, FDA486. The mutant, designated K4.3, was compared with str ain FDA486 in a wound infection model in rats. Sixty-eight percent of the rats challenged with parental strain FDA386 developed severe clini cal signs of wound infection, whereas only 29% of the animals challeng ed with isogenic mutant K4.3 showed severe symptoms (P < 0.01). The we ight loss of animals infected with the wild type was also significantl y different from that of animals infected with the mutant strain. The result demonstrates that the extracellular 19-kDa fibrinogen-binding p rotein from S. aureus contributes to the virulence in wound infection and delays the healing process.