(182b) Bacterial Separation from Blood through Sedimentational Clotting

Rapid diagnosis of blood infections presents many challenges, the first of which is fast and efficient separation of the bacteria from the blood cells. We previously developed a spinning hollow disk that separates bacteria from blood cells via the differences in sedimentation velocities of these particles. Blood was collected in EDTA tubes from volunteers and spiked with a known amount of E. coli bacteria; and then the separation of the bacteria from the blood was measured. Utilizing our spinning disk to separate the blood cells from the bacteria, we attempted to clot the red cell pack so that the plasma containing bacteria could be quickly collected without remixing with the blood cells. Clotting was induced by adding 8 M calcium chloride and adenosine diphosphate (ADP) to the blood on the disk. The CaCl2 was added to replace the calcium chelated by EDTA in the blood collection tubes. The ADP was added to induce the platelets to aggregate. Factors affecting the bacterial separation included the amount of adenosine diphosphate added to the blood, spinning parameters (speed and duration), and disk design. These factors were varied in dozens of experiments for which the concentration of bacteria in the separated plasma was measured. Results show that the best disk design contained a separation weir built into the disk, and the optimum spinning parameters were a separation sequence for 10 seconds followed by a clotting sequence for 62 s without the use of any ADP. These parameters achieved 69 ± 7% bacterial recovery from 7 mL of whole blood in 117 s. This is comparable in time and collection efficiency to previous separation of bacteria from blood using carefully designed weirs and controlled deceleration.