Binding of a Staphylococcus aureus bone pathogen to type I collagen

We contrasted the collagen-binding potential of the experimental osteomyelitis pathogen, Staphylococcus aureus strain SMH, to several other strains. These included Cowan 1 (binder), Wood 46 (non-binder) and six capsular variants. These measurements were made using an ¹²⁵I-collagen binding assay. Formalin-killed S. aureus SMH strongly bound commercial type I iodinated collagen (dissociation contant, K_d = 2 × 10^-9 m). The extent of binding was similar to Cowan 1. Binding was saturable and not inhibited by 100 mm solutions of d-glucose, d-galactose, d-mannose, methyl-α-l-fucopyranoside, l-hydroxyproline or l-glycine. d-lactose gave moderate inhibition of binding to collagen, and l-fucose was strongly inhibitory. Trypsinized SMH did not bind collagen. None of four Ruthenium-red-staining staphylococci (encapsulated) avidly bound type I collagen. The encapsulated Smith strain, for example, did not bind to collagen but its capsule-negative variant, Smith compact, showed extensive binding. Three of five non-encapsulated S. aureus were strong collagen binders. These data suggest that the prototype bone pathogen binds to the major protein component of bone's extracellular matrix. Collagen-binding is promoted by protein adhesin(s), not capsule. The latter, in fact, appeared to interfere with this interaction. Binding was inhibited by solutions containing the simple monosaccharide, l-fucose.