Platelet interaction with bacteria. II. Fate of the bacteria

Several common strains of bacteria have been studied to determine their influence on human and rabbit platelets in vitro. Bacteria at a nominal ratio of 1:1 were added to platelets in their native plasma or to platelets in a balanced salt solution. The platelet-bacterial interaction was examined by nephelometry and by sequential light microscopy of fixed specimens taken at key points in the reaction. The results support the following conclusions: (1) Bacteria that were potent stimuli of the platelet aggregation reaction were incorporated in large numbers into the forming platelet aggregates. (2) Bacteria sequestered within platelet aggregates remained in direct contact with the aggregated platelet mass for up to 1 hour in vitro and during this time showed no morphologic changes by light microscopy. (3) Plateletbacterial interaction produced clumping of the bacteria but no demonstrable killing of the microorganisms. (4) Collagen-platelet interaction resulted in release of platelet products that were capable of clumping bacteria but were not lethal to them. (5) Rabbit and human platelets showed no species differences in plateletbacterial interaction. (6) Washed platelets interacted with bacteria without added serum factors but the addition of serum accelerated the aggregation reaction.