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United States Department of Agriculture

Agricultural Research Service

Title: The Capture of Escherichia Coli 0157:h7 for Light Addressable Potentiometric Sensor (Laps) Using Two Different Types of Magnetic Beads

item Tu, Shu-I
item Uknalis, Joseph
item Irwin, Peter -

Submitted to: Journal of Rapid Methods and Automation in Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 1, 2002
Publication Date: N/A

Interpretive Summary: Contamination of pathogenic bacteria, e.g., E coli O157:H7 in foods may lead to serious public health concerns. To detect pathogens in foods, proper concentration of the target bacteria must be performed. For this purpose, immunomagnetic beads (IMB) have become a method of choice in many research laboratories. IMB can capture target pathogenic bacteria with antibodies on the beads and captured bacteria can be easily concentrated b simple magnets. However, for practical applications, factors that determine the efficiency of IMB in capturing the E. coli must be identified and optimized. Thus, we have analyzed the capture using the principles of physics, chemistry and microbiology. The theoretical predictions and experimental results were compared. The results allowed us to conclude that non-spherical IMB with larger mass are better for the capture. The information is valuable for food safety laboratories to develop practical, automated and IMB-based methodologies to detect pathogenic bacteria in foods.

Technical Abstract: Two types of commercially available, streptavidin-coated magnetic beads (SAMB) were labeled with the same biotinylated anti E. coli O157 antibodies. Labeled SAMB and other necessary antibody derivatives needed for LAPS detection were used to capture E. coli O157:H7 in solution. The LAPS signal intensity was then used to determine the overall bacterial capture efficiency. The static and hydrodynamic properties of the beads were then used to correlate with determined efficiencies. It was found that the capture increased as the total mass of SAMB increased. Also, greater capture with SAMB of a higher density was observed with the same bead mass. In addition, the SAMB of higher density also required less time of rocking to reach a maximum capture. These observations are in agreement with the predictions from the hydrodynamic properties of tested SAMB.

Last Modified: 4/21/2015
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