BacTx

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BacTx Kit for Detection of Bacterial
Contamination of Platelets
Andrew E. Levin, Ph.D.Immunetics, Inc.Blood
Products Advisory Council MeetingMarch 9, 2006
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BacTx Kit for Detection of Bacterial
Contamination of Platelet Units
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BacTx Kit Features

• lt 1 hour turnaround time
• 1 ml sample volume
• Premeasured vial reagent dispensing
• Detects both gram positives and gram negatives
• 103 104 CFU/ml assay sensitivity
• lt 10 CFU/ml detected at 24 hrs post platelet
  collection
• Absorbance readout result record

RD supported by NHLBI grant HL065877
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Bacterial Peptidoglycan Cell Wall
NAM
NAG
Peptide bridge
NAG N-Acetyl GlucosamineNAM N-Acetyl Muramic
Acid
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BacTx Assay Target Peptidoglycan

• Peptidoglycan universal component
  of bacterial cell wall both gram
  positive and gram negative species
• Common molecular structure recognized
  by peptidoglycan binding protein

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BacTx Assay Technology
Peptidoglycan binding protein (PGBP)
Enzyme
Peptidoglycan
Chromogen

• Binding of PGBP to peptidoglycan triggers
  enzymatic conversion of chromogenic substrate
  to visible product with measurable absorbance

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BacTx Assay Format

Platelet Unit
Results
30 min
10 min
1 ml
Spin down, extract
Sample
Incubate
Read Absorbance
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Assay dose-response curveBacteria spiked into
platelets
35,000
18,000
3,500
1,800
350
180
35
18
0
0
CFU/ml
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BacTx Sensitivity for Gram Positive and Negative
Bacteria
ng/ml
AABB 2004 Abstract SP47
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Time course of detection of Staph. epidermidis
spiked at 10 CFU/ml into platelet bag
Earliest detection lt 7 hours post-inoculation
AABB 2004 Abstract SP47
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Time to detection 103-104 CFU/ml BacTx vs.
BacT/ALERT
BacTxTM lt 1 hour vs. BacT/ALERT gt 8 hours
AABB 2005 Abstract SP74
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Time to Detection BacTx vs. BacT/ALERT
100 concordance
Inoculum
BacT/ALERT
BacTx
BacTx
BacTx
AABB 2005 Abstract SP74
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BacTx vs. Culture Testing Pre-screened
Negative Units
100 Concordance
BacTx
Pos
Neg
0 0
0 100
Pos
Automated culturePall BDS or Bact/ALERT
Neg
n45 13 SDP, 25 RDP, 7 Non-LR RDP
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Apheresis vs Random Donor units
Equivalent performance in BacTxTM assay
CFU/ml _at_ 48 hrs 0 0 3.6x108 6x107 8x107 7x108 5x107 9x107
Units inoculated at 10 CFU/ml, sampled for assay
at 48 hours
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RD supported by NHLBI grant HL065877