A spore-based biosensor for detecting low levels of bacteria in real-time has been recently developed. The system (termed LEXSAS, label-free exponential signal-amplification system) exploits spore's ability to produce fluorescence when sensing neighboring bacterial cells. We studied the LEXSAS as a possible approach for identifying bacterially contaminated platelet concentrates prior to transfusion because the system offers rapid analysis. high sensitivity, and low, cost. If successful, this approach could reduce the risk of morbidity and mortality front transfusion-related bacteremia and sepsis. In this study, we used the LEXSAS for detecting bacteria in platelet concentrates spiked with Bacillus cereus, Enterobacter cloacae. Escherichia coli, Pseudomonas aeruginosa. Staphylococcus aureus, or Streptococcus pyogenes. Bacteria were separated from platelets using a 2-min procedure based on bacterial resistance to detergents and osmotic shock. The results indicate that the LEXSAS could be used to design a practical biosensor for identifying bacterially contaminated platelets in real-time. (C) 2002 Elsevier Science (USA). All rights reserved.