Effect of whole plasma and purified plasma proteins onS agalactiae–induced aggregation of GFPs. Cells of S agalactiae 6313 (1 × 10⁹) were preincubated for 1 hour with 1 mL whole human plasma, human serum, or 0.9% solution of NaCl (A) or physiologic concentrations of Fbg (3 mg/mL), fibronectin (300 μg/mL), or albumin (35 mg/mL; panel B). Bacteria were harvested by centrifugation, washed, and adjusted to 1 × 10⁹ cells/mL. Then 50 μL of the bacterial suspensions was added to 0.4 mL GFPs (4 × 10⁸) in HEPES buffer supplemented with 1.25 mM CaCl₂ and 5.5 mM glucose, pH 7.4, and the samples were monitored in an aggregometer for turbidity. Results are representative of 3 different experiments.