BacTx Test for Bacterial Contamination of Platelets
Rapidly detecting bacteria in platelet units presents a major challenge. To be effective, a test must be sensitive enough to detect the bacterial load in a contaminated platelet bag, and with a fast enough turn around time that it can be performed close to the time of transfusion.
Some tests are ineffective because of low sensitivity. Others are overly difficult or time consuming to perform close to transfusion. According to the American Association of Blood Banks, a rapid test with high sensitivity performed close to transfusion would represent a breakthrough in transfusion safety. This need is particularly acute in whole blood-derived or random donor platelet units, for which culture testing is not practical. BacTx is a rapid assay for the detection of bacterial contamination of platelets that can be used to test both apheresis units and single or pooled random donor units.
BacTx has a validated threshold sensitivity of 104 CFU/ml for a range of bacterial pathogens, including both gram-positive and gram-negative species associated with platelet contamination. This level of sensitivity meets the guidelines recommended by the U.S. Food and Drug Administrations Blood Products Advisory Committee for detection of levels of bacterial contamination in platelets which are high enough to cause serious or fatal illness in transfusion recipients.
Additionally, BacTx has demonstrated the capability to detect bacterial pathogens inoculated into platelets at very low concentrations similar to those occurring in actual cases of contamination, after the typical 24 48 hour quarantine period following collection. The rapid turnaround time of the BacTx assay ensures results in less than one hour, at the same time that automated culture bottles have just been inoculated with platelet samples and left to incubate. The time savings means that the contamination status of platelet units can be known much earlier in their inventory cycle.
Methodology
Peptidoglycan is a universal component of the bacterial cell wall in both gram positive and gram negative species. This common molecular structure is recognized by a Peptidoglycan Binding Protein (PGBP) in the BacTx assay.
BacTx Assay Target: Peptidoglycan
The Technology
The BacTx test detects the presence of Peptidoglycan (PG), which is a component of bacterial cell walls in both gram-positive and gram-negative bacteria, and (1-3)-â-D-glucan in fungi and yeast.
To test platelet preparations for the presence of bacterial PG, platelets are separated from plasma and concentrated by brief centrifugation, which pellets both platelets and bacterial contaminants, if present. The platelet pellet is then subjected to an extraction step, which solubilizes platelet cells and efficiently releases PG from bacterial cell walls for optimal detection. Extracted platelets are combined with the detection reagent and placed in the BacTx optical reader, which monitors the reaction kinetically. The reaction produces a red colored product if bacteria are present in the platelet sample. If the sample produces a red color within the specified reading time the reader will register the sample as positive and alert the operator with an audible alarm. Otherwise, the sample will be passed as negative for bacteria at the end of the time period.
BacTx Assay Principle
BacTx Reader and Software
Features and benefits:
- Automated reading process for test samples
Reader accepts up to 8 samples
- Random access or batch mode for reading
- Reader issues visual and audible alert when bacteria detected
- Sample ID entered by user links platelet unit and assay result
- Results can be printed or uploaded as permanent record
- Reader operates with standard Windows PC
- Reader has small footprint, saves bench space
