Progress 12/08/10 to 09/30/13
Outputs Progress Report Objectives (from AD-416): 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). Approach (from AD-416): 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. The start of this project was delayed by the unexpected depature of the California State University graduate student assigned to work on it. However, with the new student on-board we screened several commercial media for appropriateness in culture of both the protozoa and bacteria of interest. We have also developed experimental conditions that simultaneously support both predation of non-STEC and protozoan lethality with Shiga toxin-producing Escherichia coli (STEC). While this experimental system is now working, it remains to be determined whether we can create a robust commercial STEC-specific growth medium based on protozoan co-culture. The Cooperator provides media and technical advice. The ADODR documents material shipments and consults the Cooperator via telephone and email communications. In FY12, a new culture method for detection of STEC was developed base7d on a highly selective medium that promotes the production of Stx by cultured STEC. This medium has now been commercialized by Hardy Diagnostics. This medium facilitates the identification of STEC that are responsible for an estimated 265,000 infections each year in the US, including some fatalities. This medium can be incorporated into tests that would minimize the time needed for analysis, while enabling recovery of STEC from contaminated foods, thus enhancing the capabilities of industry and government to assure food safety. In FY13, a new commercial medium was developed that facilitates the identification of STEC. This medium reduces the time taken for recovering STEC from contaminated food. The medium was recently reformulated by the Cooperator, and validation studies are nearly complete. Research progress reported addresses objective 1: "Develop new assays for bacterial toxins and their variants, using immunological and other methods, with emphasis on applicability to practical problems facing the food industry and regulatory agencies" of the parent project.
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Progress 10/01/11 to 09/30/12
Outputs Progress Report Objectives (from AD-416): 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). Approach (from AD-416): 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). In FY12 a new culture method for detection of Shiga toxin-producing E. coli (STEC) was developed based on a highly selective medium that promotes the production of Stx by cultured STEC. This medium has now been commercialized. This medium facilitates the identification of STEC that are responsible for an estimated 265,000 infections each year in the US, including some fatalities. This medium can be incorporated into tests that would minimize the time needed for analysis, while enabling recovery of STEC from contaminated foods, thus enhancing the capabilities of industry and government to assure food safety. Research progress reported, addresses objective 1 of the parent project.
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