Monitoring the physiologic stress response: a novel biophysical approach for the rapid detection of bacteria in platelet concentrate

Abstract

Currently approved culture-based methods for the bacterial testing of platelet concentrates (PCs) require an extended period of time to obtain results. A new approach based on the monitoring of the bacterial response to physiologic stress is presented. Because the stress response is independent of the growth rate, decisive results can be obtained in near real time. PCs were spiked with Gram-positive Staphylococcus epidermidis and Propionibacterium acnes and Gram-negative Escherichia coli organisms commonly implicated in posttransfusion septic reactions. All suspensions were treated with Triton X-100 at concentrations that caused human cell lysis while acting as a stressor for bacterial cells. Normalized impedance response (NIR) profiles of these suspensions were recorded using the BioSense Technologies differential impedance sensing platform specifically designed to monitor subtle changes in the dielectric properties of biologic suspensions. Further development of the approach included measurement of NIRs for spiked PCs treated with nonlysing chemical stressors. NIR profiles for bacteria conventionally growing under optimal conditions were characterized by an overall increase in the NIR values. In contrast, the corresponding responses from chemically stressed bacteria revealed immediate and continuous decreases in value-enabling bacterial detection in less than 30 minutes. These pilot experiments demonstrated that monitoring of the bacterial stress response is a fast and effective way to detect bacteria in PCs. In addition, special culture conditions are not required for detecting anaerobes and fastidious species.