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Develop a New Microbiological Medium for Selective Cultural Enrichment of Stec


The objective of this cooperative research project is to develop a microbiological growth medium that is selective for Shiga toxin-producing Escherichia coli bacteria (STEC).

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The principle of the STEC-selective medium is based upon competition between STEC and another microorganism. At least one recent scientific publication suggests the protozoan Tetrahymena thermophila is capable of killing E. coli that do not express Shiga toxin, while STEC can kill the protozoan. If STEC are present, they may be the only organisms capable of growth on the media. Developing the new media based on an existing E. coli selective medium will help in negative selection against non-E. coli toxin producers, which might otherwise compete against STEC and the protozoan. Additional selection may be applied in a modified pre-amplification culture, before plating on the new media. For validation, STEC will be spiked into foods and the Lower Limit Of Detection determined. Documents NFCA with Hardy Diagnostics. Formerly 5325-42000-043-08N (4/11).

Carter, John Mark
USDA - Agricultural Research Service
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