New method for detecting spores of non-proteolytic Clostridium botulinum

The Institute of Food Research has collaborated in the development of a new method for detecting spores of non-proteolytic Clostridium botulinum.  This bacterium is the major health hazard associated with refrigerated convenience foods, and these developments give the food industry and regulators more quantitative information on which to base the procedures that ensure food safety.

Botulism is a rare but deadly form of food poisoning that can be caused by consuming tiny quantities of botulinum neurotoxin. The botulinum neurotoxin is the most potent toxin known (just 30ng of neurotoxin is sufficient to cause illness and even death), and the consumption of as little as 0.01g of food in which C. botulinum has grown can result in botulism. 

The majority of cases of foodborne botulism are caused by two bacteria known as non-proteolytic C. botulinum and proteolytic C. botulinum. A major difference between these two bacteria is that non-proteolytic C. botulinum is able to grow and produce toxin at 3°C, whilst proteolytic C. botulinum will not grow at temperatures less than 12°C.  This ability to grow at form toxin at refrigeration temperatures makes non-proteolytic C. botulinum a major hazard in minimally heated refrigerated foods, such as chilled ready meals.

The production incorporates practices and risk assessments based on the latest scientific information, such as spore heat resistance, growth properties of non-proteolytic C. botulinum, and the incidence of these spores in food. The new method of detecting non-proteolytic C. botulinum is providing high quality information on the incidence of spores in food.  An important feature of the new method is that it is specific, and enumerates only non-proteolytic C. botulinum spores.  Some previous techniques were not optimised to distinguish between non-proteolytic C. botulinum and proteolytic C. botulinum.  The new method is very sensitive with a low detection limit that has been achieved by the use of a selective enrichment and large test samples, and importantly this has been confirmed using carefully structured control samples.

The robust method was developed as a collaboration between the Nestlé Research Centre, Switzerland and IFR, an institute of the Biotechnology and Biological Sciences Research Council (BBSRC) and is designed to provide the data the food industry needs for quantitative microbial risk analysis and the implementation of food safety objectives.  This allows the total risk from spores of non-proteolytic C. botulinum in the final meal to be calculated.  Modelling the risk of this total spore count rising above safe levels and the frequency that this event occurs will allow the management and control of the process more accountably.