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United States Department of Agriculture

Agricultural Research Service

Title: Sensitive Detection of Escherichia Coli 0157:h7 by the Use of Immunomagnetic and Fluorescent Beads

Authors
item Tu, Shu-I
item Cooke, Peter
item Paoli, George
item Gehring, Andrew

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: February 15, 2006
Publication Date: May 1, 2006
Citation: Tu, S., Cooke, P.H., Paoli, G., Gehring, A.G. 2006. Sensitive detection of escherichia coli 0157:h7 by the use of immunomagnetic and fluorescent beads. Meeting Abstract.

Technical Abstract: To meet the needs of food safety, a rapid and sensitive fluorescent sandwich method for the detection of Escherichia coli O157:H7 in ground beef was developed. Immunomagnetic beads (IMBs) coated with anti-E. coli O157:H7 antibodies were used to capture and concentrate E. coli O157:H7 present in ground beef. Streptavidin-coated fluorescent beads were used to react with biotin-labeled anti-E. coli O157:H7 to form immunofluorescent beads (IFBs). The IFBs were used to detect the E. coli O157:H7 captured by the IMBs by forming (IMB)M–(E. coli O157:H7)N –(IFB)O sandwich complexes, where M, N and O were variable but integral numbers. This sandwich technique was able to detect 1000 cfu/mL of the bacterial suspensions from a quantified and diluted broth culture. The method was then applied to detect E. coli O157:H7 in artificially contaminated ground beef. Known quantities of freshly cultured cells of E. coli O157:H7 were added to 25-g ground beef patties held in sterile bags with filters. The inoculated patties were stored at 7C overnight; a volume of 75 mL of enrichment broth was added to each sample, and the bags were incubated at 40C with shaking at 160 rpm for 4.5 h. After enrichment, cells of E. coli O157:H7 in the filtrate were captured and concentrated with IMBs and further conjugated with IFBs for detection. The results demonstrate that, after a 4.5-h enrichment period, the developed procedure can detect the presence of E. coli O157:H7 in ground beef previously spiked at a level of 1 cfu/g.

Last Modified: 9/10/2014
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