(372a) Rapid Detection of Bacteria in Blood for the Early Diagnosis of Sepsis

Sepsis, (systemic inflammation caused by bacterial infection of blood) is a leading cause of death in the US with a mortality rate of ~ 30%. The clinical symptoms displayed by the patients are subtle and non-specific. At the time clinical symptoms begin to be displayed, the concentration of bacteria present in their blood is often as low as 1-10 CFU/ml. If allowed to progress, the disease leads to multiple organ failure and ultimately death. Multiple studies have shown that the quicker one can detect the presence of bacteria, and start effective antibiotic therapy, the greater is the likelihood of survival for the patient. The current technologies for this purpose are Automated Blood Culture Systems such as the BACTEC, BacT/Alert and VITEK, which take 1-5 days to obtain the result.

Unlike the current culture systems that detect the presence of bacteria in the suspensions indirectly via the effects of bacterial metabolism (change in pH of levels of O₂/CO₂), we use a novel technique that relies on the fact that bacteria can store large amount of charge and thus increase the bulk capacitance of the liquid in which they are suspended. An increase in the number of bacteria leads to an increase in the bulk capacitance of the suspension. Usually changes in the bulk capacitance are masked by the electrochemical interfacial (double layer) capacitance. But by leveraging microfluidic geometry, and taking measurements at multiple frequencies, we are able to accurately monitor changes in the bulk capacitance. Doing so enables us to pick up signatures of bacterial presence in the suspension at concentrations of ~ 1000 cfu/ml (as opposed to > 10⁶ cfu/ml for current technologies), and detect the presence of ~10 E coli /ml within 4 hours, as opposed to ~20 hours required by current technologies.