Bacterial contamination of platelets is considered the greatest infectious risk of blood product transfusion today. The incidence of bacterially contaminated platelet units may be as high as 1 in 2000, which is several orders of magnitude greater than that for HIV. Bacterial contamination at high levels can lead to severe morbidity or mortality in transfusion recipients. It is likely that the number of deaths due to transfusion- associated sepsis is underestimated, as many cases are not traced back to determine the source of infection. Existing technologies to detect bacterial contamination of platelet units are either very slow (e.g., culture methods which take 36-48 hours to generate a result) or very insensitive (e.g., pH or glucose dipstick testing which cannot detect bacteria at concentrations below about 107 CFU/ml.) To address this need, we have developed a robust screening test for detection of bacterial contamination in platelet units. The BacTx"""""""" assay is rapid (total time 45-50 minutes), sensitive (100-10,000 CFU/ml, depending on the strain,) and specific (>99.5%). However, the assay is currently configured to be run in a laboratory by trained personnel as it requires accurate pipetting and centrifugation steps. In this project, we propose to redevelop the assay to replace these laboratory procedures with a simple filtration-based approach, carried out in a compact device that can be operated by non-specialized personnel outside the laboratory. Our approach will rely on separation of platelets from bacteria with a platelet depletion filter, followed by capture, concentration and release of bacteria or bacterial products from a bacterial capture filter. The filtration steps will take only about 5 minutes to perform, followed by a 30 minute walk-away assay, and will not require any specialized technical skills. In this format, the BacTx"""""""" assay will become a near point of care assay that can be performed immediately prior to transfusion, a significant advance over existing culture methods which give information about the sterility of a platelet unit based on a sample taken one or more days in the past. Implementation of the proposed rapid assay may permit a paradigm shift in blood banking, allowing an extension of the storage life of platelet units from 5 to 7 days. The added shelf life will increase platelet inventories and lead to cost savings by eliminating the requirement to dispose of otherwise viable platelet units that have reached the 5-day expiration limit. To date, other means such as culture testing at the point of collection have been found inadequate to ensure the safety of 7-day old platelets, precluding their use. Once developed, the BacTx"""""""" rapid assay will be validated through spiking studies designed to determine the sensitivity of the assay for the range of bacterial pathogens typically found as contaminants in platelets. In Phase I, we will develop, build and evaluate various prototype designs for the rapid test. Physical prototypes will be designed and constructed with the help of engineering collaborators. The optimal design will be brought to final development, manufacturing and clinical validation in Phase II.
Bacterial contamination of platelets is a serious risk to transfusion recipients, potentially resulting in severe illness or death. Current methods to test for bacteria in platelets are slow and unreliable, however. This project is aimed at development of a rapid and sensitive test for bacterial contamination which can be performed shortly before transfusion, improving the safety of the U.S. blood supply.
