Distribution of fibronectin-binding proteins among group A streptococci of different M types.

Binding of fibronectin by group A streptococci (GAS) promotes adherence to epithelial cells. The fibronectin-binding activity and the presence of prtF, a gene encoding a fibronectin-binding protein, were studied among 109 strains. Fifty-six strains of 42 different M types possessed prtF-related genes, and 89% of these strains bound fibronectin at high levels. The prtF-related genes varied in the number of repeats that constitute one of its two fibronectin-binding domains. Fifty-three strains of 21 different M types lacked prtF. Thirty-nine of these (74%), representing 13 different M types, bound fibronectin at very low levels. However, 9 (17%), of 5 different M types, bound fibronectin at high levels. The presence of prtF and the capacity to bind fibronectin correlated strongly with the M type of various strains of GAS. This correlation may suggest the existence of a relationship between fibronectin binding and the pathogenic potential of GAS.