Limitations for platelet aggregation induced by H pylori. PRP (100 × 10⁶ platelets) and Helicobacter pylori (OD 0.1 to OD 1.0, equivalent to 1 × 10⁶ CFU to 10 × 10⁶ CFU) mixtures (platelet/bacteria ratio from 100:1 to 10:1, respectively) were used for aggregation assay. (A-B) Platelet aggregation occurs in a bacteria concentration- and storage time-dependent manner. The threshold for aggregation is H pylori more than or equal to OD 0.2 (platelet/bacteria ratio = 50:1) with a bacteria storage time of more than or equal to 4 hours. (C) Platelet aggregation occurred in some H pylori strains (ATCC 49503 and occasionally ATCC 51932).