Incidence of the highly conserved fib gene and expression of the fibrinogen-binding (Fib) protein among clinical isolates of Staphylococcus aureus.

We have recently described a 19-kDa fibrinogen-binding protein, termed Fib, which is secreted into the extracellular medium by Staphylococcus aureus. In this study, the presence of the Fib protein and the fib gene among clinical isolates of S. aureus and among other staphylococcal species known to interact with fibrinogen was investigated. This task was pursued at the DNA, mRNA, and protein levels. It was found that the fib gene was unique to S. aureus and highly conserved at the nucleotide level. The Fib protein was produced by all S. aureus strains investigated but was not detected in all bovine mastitis strains, because of proteolytic degradation by simultaneously produced staphylococcal proteases. It was concluded that the fib gene was unique to S. aureus and that it could be used in the identification of S. aureus.