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Appl. Environ. Microbiol., 02 1996, 587-592, Vol 62, No. 2
H Yu and JG Bruno
Hemorrhagic Escherichia coli O157:H7 strains and other virulent enteric
pathogens can pose a serious health threat in tainted meats, poultry, and
even drinking water. Traditional culture-based methods for assay of enteric
pathogens in foods and water sources are relatively slow, and results can
be ambiguous. Immunomagnetic separation (IMS) and detection methods have
been investigated and appear promising for rapid bacterial assay of foods
and environmental samples. In this work, a commercial sensor which combines
IMS with electrochemiluminescence (ECL) detection is evaluated for
detection of E. coli O157 and Salmonella typhimurium in foods and fomites.
Results indicate that detection limits are in the range of 100 to 1,000
bacteria per ml in pristine buffer for E. coli O157 and S. typhimurium,
respectively, or 1,000 to 2,000 bacteria per ml in food samples (depending
on the sample) and that total processing and assay time is rapid (< 1 h)
even in food samples. An immunologic "hook" or high-antigen-concentration
prozone effect was observed above 10(4) and 10(5) bacteria per ml for E.
coli O157 and S. typhimurium, respectively. IMS was accomplished in milk,
juices, serum, supernatant fluids from ground beef, finely minced chicken,
and fish suspensions as well as several freshwater sources and followed by
ECL assay. Some samples, especially fish, gave unexpectedly high background
ECL. Conversely, low ECL intensity was observed in nonfat and 2% fat milk
samples, which appeared to be related to binding or entrapment of the
antibody-coated magnetic beads by particulates in the milk, as revealed by
microscopy. Results of this evaluation suggest the feasibility of
immunomagnetic-ECL methodology for rapid, sensitive, and facile preliminary
screening of various foods and fomites for the presence of virulent enteric
pathogens.
Copyright © 1996, American Society for Microbiology
Immunomagnetic-electrochemiluminescent detection of Escherichia coli O157 and Salmonella typhimurium in foods and environmental water samples
Systems Research Laboratories, Inc., U.S. Army Edgewood Research, Development, and Engineering Center, Aberdeen Proving Ground, Maryland 21010, USA.
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