Comparison of staphylococcal clumping factor and protein A.

Protein A (3, 8) and the clumping factor (bound coagulase; 1) of Staphylococcus aureus share common characteristics, yet, to our knowledge, they have not been compared to determine possible identity. Both are protein, antigenic, cell surface components of S. aureus but not of S. epidermidis, and both are released into the culture medium as growth develops. Protein A is a common agglutinogen of serologically diverse types of S. aureus (5). Clumping factor also occurs as a common antigen in various S. aureus strains (7). Clumping factor-negative mutants which are