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The aims of this project were:<br><ul>
<li>To establish the proportion of C. butyricum strains isolated from natural sources that carry the botulinum neurotoxin gene
<li>To determine whether C. tertium and C. bifermentans produce toxins
<li>To define the conditions of temperature, pH and solute concentration that will prevent growth of C. butyricum, C. tertium, C. bifermentans and C. barati.
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The microbiological safety of food depends on ensuring that pathogenic microbes are eliminated from food or prevented from growing.
<p>For most of the well-known microbial pathogens the conditions necessary to achieve this have been worked out in considerable detail over many years.
<p>However from time to time new hazards emerge and information about the properties of the new organisms becomes necessary.
<p>In recent years certain strains of Clostridium butyricum and Clostridium barati have been isolated that produce neurotoxins very similar to those produced by Clostridium botulinum types E and F respectively.
<p>Initially these organisms were associated with infant botulism but C. butyricum has also been implicated in foodborne illness.
<p>A different example of a possible new hazard is illustrated by a product recall based on high numbers of Clostridium tertium and Clostridium bifermentans in pate.
<p>Though neither of these organisms is associated with foodborne illness the counts were sufficiently high to cause concern. With all three organisms there is a need for more information about their growth characteristics and properties in relation to food safety.
<p>The experimental plan was to develop and use a selective enrichment medium to isolate C. butyricum from food and environmental samples, and then to screen isolates for the presence of the type E toxin gene using the polymerase chain reaction (PCR).
<p>Testing for possible toxicity in C. tertium and C. bifermentans was based on screening culture filtrates for toxic effects against cultured Vero cells.
<p>Growth limiting pH values, solute concentrations (sodium chloride, sucrose) and temperatures for growth were determined by inoculating replicate tubes of growth medium with spore inocula of test organisms derived from a cocktail of non-toxigenic strains or toxigenic ones.
<p>Find more about this project and other FSA food safety-related projects at the <a href="http://www.food.gov.uk/science/research/" target="_blank">Food Standards Agency Research webpage</a>.