Staphylococcus aureus strains isolated from patients with septic arthritis or osteomyelitis possess a collagen receptor present in two forms, which contains either two or three copies of a 187-amino-acid repeat motif. Collagen receptor-positive strains adhered to both collagen substrata and cartilage in a time-dependent process. Collagen receptor-specific antibodies blocked bacterial adherence, as did preincubation of the substrate with a recombinant form of the receptor protein. Furthermore, polystyrene beads coated with the collagen receptor bound collagen and attached to cartilage. Taken together, these results suggest that the collagen receptor is both necessary and sufficient to mediate bacterial adherence to cartilage in a process that constitutes an important part of the pathogenic mechanism in septic arthritis.

(Pro-Gly-Pro)., (Pro-Pro-Gly)jo, and (Pro-OH-Pro-Gly)j0 were recognized by the receptor, whereas the peptides (Pro-Ala-Gly). and polyproline showed no inhibitory activity.The matrix proteins fibronectin and laminin may mediate the substrate adhesion of eucaryotic cells, and putative receptors present on the surfaces of cells are believed to recognize distinct sites in the adhesive proteins (35). Some eucaryotic cells (e.g., hepatocytes and chondrocytes) may also adhere to collagen substrate, and the presence of collagen-specific receptors has been implicated (18,22). The collagen receptor on hepatocytes appears to have broad specificity, since it binds to several different types of collagen as well as to isolated collagen a chains, collagen peptides, and synthetic collagen analogs (22).In the process of tissue adherence of pathogenic bacteria, structures at the host cell surface or in the extracellular matrix are recognized by specific receptors present on the bacterial cells. Previous studies have shown that bacteria may bind to fibronectin (7, 15, 23, 25, 26, 32), laminin (7, 16, 27, 29, 32), and collagen (3, 7, 12, 32) Chemicals. Type II collagen was purified from bovine nasal septum as described by Strawich and Nimmi (28). Native collagen types I and III were isolated with neutral salt from fetal bovine skin and purified by NaCl precipitation and DEAE chromatography (30). Type IV collagen was isolated from mouse tumor (31). Type V and VI collagens were purified from a pepsin digest of human placenta (1,20). The 1(I) and 2(I) chains both from calf and rat skin type I collagens were purified by carboxymethyl cellulose chromatography (21). The rat a chains were treated with cyanogen bromide, and the generated peptides (CB peptides) were purified as previously described (2, 6). The isolated peptides included CB2, CB5, CB6, CB7, and CB8 from the 1(I) chain and CB3, CB4, and CB5 from the a2 chain of rat type

Bacteroides (Porphyromonas) gingivalis, which has been implicated as an etiologic agent in human periodontal diseases, has been shown to bind and degrade human fibrinogen. B. gingivalis strains bind fibrinogen reversibly and with high affinity and bind to a specific region of the fibrinogen molecule that appears to be located between the D and E domains (M. S. Lantz, R. D. Allen, P. Bounelis, L. M. Switalski, and M. Hook, J. Bacteriol. 172:716-726, 1990). We now report that human fibrinogen is bound and then degraded by specific B. gingivalis components that appear to be localized at the cell surface. Fibrinogen binding to bacterial cells occurred at 4, 22, and 37 degrees C. A functional fibrinogen-binding component (Mr, 150,000) was identified when sodium dodecyl sulfate-solubilized bacteria were fractionated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, transferred to nitrocellulose membranes, and probed with 125I-fibrinogen. Fibrinogen degradation did not occur at 4 degrees C but did occur at 22 and 37 degrees C. When bacteria and iodinated fibrinogen were incubated at 37 degrees C, two major fibrinogen fragments (Mr, 97,000 and 50,000) accumulated in incubation mixture supernatant fractions. Two major fibrinogen-degrading components (Mr, 120,000 and 150,000) have been identified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis in substrate-containing gels. Fibrinogen degradation by the Mr-120,000 and -150,000 proteases was enhanced by reducing agents, completely inhibited by N-alpha-p-tosyl-L-lysyl chloromethyl ketone, and partially inhibited by n-ethyl maleimide, suggesting that these enzymes are thiol-dependent proteases with trypsinlike substrate specificity. The fibrinogen-binding component could be separated from the fibrinogen-degrading components by selective solubilization of bacteria in sodium deoxycholate.

Fibronectin, a major protein component of plasma and loose connective tissue has previously been shown to bind to several strains of Staphylococcus aureus. We examined a large number of strains of different species of Staphylococcus with respect to their ability to bind fibronectin. The relative numbers of strains defined as fibronectin-binders among the different species were as follows: S. aureus (22 of 23), S. haemolyticus (5 of 5), S. warneri (8 of 11), S. hyicus (5 of 6), S. hominis (13 of 17), S. saprophyticus (11 of 20), S. epidermidis (4 of 7), and S. simulans (8 of 10). Only three species showed a predominance of nonbinders over binders: S. capitis (4 of 14), S. xylosus (0 of 4), and S. cohnii (3 of 11). These data indicate that staphylococcal species isolated from soft tissue infections frequently have the ability to bind fibronectin and suggest that the ability to bind to this protein may contribute to the virulence of coagulase-positive and coagulase-negative staphylococci.