(229b) Rapid Separation of Bacteria from Whole Blood for Sepsis Diagnosis

Sepsis is a severe blood infection that is caused by bacteria in the blood stream. If the bacteria are antibiotic resistant, the mortality rate of this infection is very high. The current clinical methods to diagnose sepsis require culturing the blood sample prior to diagnostic procedures to identify the bacteria and their resistance profile. Culturing the blood samples is a time-consuming step and the mortality rate of the sepsis increases as the time passes. It is crucial to find methods of diagnosing sepsis that do not need culturing the samples. Identification of bacteria is possible using molecular diagnostics (DNA analysis), but since blood cells interfere with these types of analyses, they must be separated from the bacteria first.

We have developed a method for rapid separation of the bacteria from whole blood based on sedimentation velocities in a centrifugal field. Various blood cells and bacteria have different sizes and will have different sedimentation velocities. Spinning blood in our hollow disks creates 2 layered phases: a layer of blood cells and a layer of plasma. While blood cells and bacteria have similar densities, blood cells sediment 30-fold or more faster than bacteria. The red cells and white cells will quick form a layer at the outer wall of the spinning hollow disk and the slower bacteria will remain in the plasma. By carefully reducing the spinning speed, we are able to separate the plasma containing the bacteria from rest of the blood cells.

This presentation describes our research and results in studying the parameters of hollow disk size, spinning speed, and spinning time on removing cells and retaining bacteria in the plasma. Our results show that we are able to separate and recover about 50 percent of the bacteria from 7 ml of whole blood in about 1 minute spinning followed by careful deceleration of the disk. More than 95% of the cells are removed from the plasma. This spinning disk technology can be easily implemented in a clinical setting.