Staphylococcus aureus fibronectin-binding protein (FnBP)-mediated adherence to platelets, and aggregation of platelets induced by FnBPA but not by FnBPB.
BACKGROUND
The ability of Staphylococcus aureus to adhere to platelets and to induce aggregation of platelets is considered to be a critical factor in S. aureus-associated infective endocarditis.


METHODS
To identify and characterize further bacterial factors involved in the S. aureus-platelet interaction, we generated a phage-display library of S. aureus genomic DNA by use of the improved phagemid vector pG8SAET. The library was affinity-panned against gel-filtered, immobilized platelets.


RESULTS
Repeatedly isolated clones contained overlapping DNA fragments encoding a portion of the S. aureus fibronectin (Fn)-binding proteins (FnBPs). In a flow cytometric adherence assay, Staphylococcus carnosus that heterologously expressed either fnbA or fnbB, which encode FnBPA and FnBPB, respectively, showed increased adherence to activated, gel-filtered platelets. Adherence was promoted by the addition of Fn or fibrinogen (Fg), which most likely act as bridging molecules. Interestingly, promotion of adherence mediated by Fn was in the same range with S. carnosus producing either FnBPA or FnBPB, whereas promotion of adherence mediated by Fg was significantly more pronounced with S. carnosus that produce FnBPA than with S. carnosus that produce FnBPB. Furthermore, FnBPA, but not FnBPB, mediated aggregation of platelets when present on S. carnosus cells.


CONCLUSIONS
Our results indicate a substantial functional difference between FnBPA and FnBPB in the S. aureus-platelet interaction.
Heilmann
Christine
C
Institute of Medical Microbiology, University of Munster, Munster, Germany. heilmac@uni-muenster.de
Niemann
Silke
S
Sinha
Bhanu
B
Herrmann
Mathias
M
Kehrel
Beate E
BE
Peters
Georg
G
D018829:Adhesins, Bacterial / Q000378:metabolism*; D000328:Adult; D000595:Amino Acid Sequence; D001422:Bacterial Adhesion; D001426:Bacterial Proteins / Q000378:metabolism*; D001792:Blood Platelets / Q000382:microbiology; D002352:Carrier Proteins / Q000378:metabolism*; D004279:DNA, Viral / Q000737:chemistry / Q000302:isolation & purification; D004697:Endocarditis, Bacterial / Q000382:microbiology; D005340:Fibrinogen / Q000378:metabolism; D005353:Fibronectins / Q000378:metabolism; D015698:Genomic Library; D006801:Humans; D008969:Molecular Sequence Data; D019151:Peptide Library; D010974:Platelet Aggregation; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D013210:Staphylococcus / Q000235:genetics; D013211:Staphylococcus aureus / Q000378:metabolism* / Q000472:pathogenicity*
D018829:Adhesins, Bacterial; D001426:Bacterial Proteins; D002352:Carrier Proteins; D004279:DNA, Viral; D005353:Fibronectins; D019151:Peptide Library; C078635:fibronectin-binding proteins, bacterial; D005340:Fibrinogen