BacTx® Rapid Test for Bacterial Contamination of Platelets



Immunetics has received U.S. Food and Drug Administration (FDA) clearance for its BacTx rapid test for bacteria in apheresis platelets.

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The BacTx rapid test is a colorimetric assay that can detect aerobic, anaerobic, gram-negative and gram-positive bacteria in a single test. It combines high sensitivity with simple, easy workflow integration to significantly improve patient safety at the point of transfusion. The assay utilizes a patented, highly specific, universal bacterial detection reagent that has been shown to detect wild and cultured bacterial strains.

The BacTx rapid test meets AABB standard 5.1.5.1.1. and is intended for use at the transfusion site on the day of issue. Bacterial contamination of platelets represents the greatest infectious risk to patients in transfusion medicine. It is a worldwide problem that has not been satisfactorily solved and puts transfusion patients — particularly those most vulnerable to disease — at greater risk of serious illness or death from a contaminated platelet transfusion.

The BacTx assay can be used for quality control testing of:

  • Leukocyte-reduced apheresis platelets (LRAP) within 24 hours of transfusion, following testing with an FDA-cleared growth-based bacterial detection device.
  • Pools of up to six units of leukocyte-reduced whole-blood derived platelets that are pooled within 4 hours of transfusion.
Principle of the test

The BacTx test detects peptidoglycan, a cell wall component of both gram-positive and gram-negative bacteria. A peptidoglycan binding protein initiates a series of enzymatic reactions that convert a substrate to a visible color. In the presence of bacteria, color will develop at a rate proportional to the level of bacterial contamination. The BacTx analyzer and software automatically monitor the reaction as color intensity changes. This provides a kinetic test that rapidly detects bacterial contamination and flags any contaminated platelet units.

Test procedure
A 0.5 mL sample is removed sterilely from a platelet bag and processed through several quick steps, then added to the BacTx reagent tube. Up to 8 samples can be processed in parallel in 15 minutes. The tubes are placed in the BacTx analyzer, which continuously monitors color development. Test results are displayed and automatically interpreted by the BacTx software. The assay is complete in 30 minutes or less, depending on the level of contamination. A highly contaminated platelet sample (e.g., 106 CFU/mL or higher) will begin to change color within minutes and will be flagged as a “fail” by the software as soon as the detection threshold is crossed. If no contamination is detected after 30 minutes of incubation, the platelet bag is flagged as a “pass.”

Complete System
The BacTx Rapid Assay System* is designed to easily integrate with your laboratory workflow.

The system provides the reagents, reaction and sample tubes, analyzer, and software needed for sample processing, reading, and interpretation. You provide only the pipettor, microcentrifuge, vortex mixer, and tube rack.

*The BacTx® Kit, reagents, and associated protocols are covered under U.S. Patent 7,598,054, and other foreign and pending patents.

BacTx Publications

  • Jacobs, MR et al. Detection of Bacteria in Leukocyte-Reduced Whole Blood Derived Platelet Units using the Immunetics BacTx® Test. 2010, Presentation at AABB Meetings. Download pdf
  • Krueger NX et al. Slow Growing Bacterial Strains in Platelet Units Evade Detection with Culture Systems But Are Detected by the BacTx™ Assay, a Rapid Test for Bacterial Contamination of Platelet Units. 2009, Presentation at AABB Meetings. Download pdf
  • BacTx™ Assay for Bacterial Contamination of Platelets Detects Bacteria Missed by Automated Culture Systems. 2008, Presentation at AABB Meetings. Download pdf