Botulism and food safety
Botulism is caused by neurotoxin formed by the Clostridium botulinum bacterium, and is one of the most deadly foodborne diseases. The botulinum neurotoxin causes paralysis that can lead to death by respiratory failure.
Scientists at the Institute of Food Research (IFR, an institute of BBSRC) have developed computer models to predict whether the bacteria will grow under different combinations of factors such as temperature, pH and salt concentration. The data are used by the food industry to design formulations and heating processes to prevent growth from spores of C. botulinum, and are important in the development of new foods and modified food processes.
The consumption of as little as 0.01g of food in which C. botulinum has grown can result in botulism, and just 30ng of neurotoxin is sufficient to cause illness and even death. C. botulinum can grow and form toxin at temperatures as low as 3.0°C.
Around 150 cases of botulism are reported each year in the US. More than half of these are associated with infant botulism, with the remainder associated with foodborne botulism or wound botulism. All three types of botulism are recorded in the UK.
A Clostridium botulinum spore. Image: Mike Peck
Professor Mike Peck, Acting Programme Leader (Bacterial Foodborne Pathogens) at IFR, says the economic and social costs associated with foodborne botulism are immense. “The fatality rate is in the region of 10% of cases, while full recovery may take months or even years. It is estimated that the economic cost per case associated with commercial food is $30M in the US.” He adds that stringent precautions taken by industry ensure that foodborne botulism is rare in the UK.
C. botulinum and its neurotoxin are important for other reasons. The neurotoxin is an important pharmaceutical product and is used as a therapeutic agent to treat a number of debilitating conditions, such as torticolis, a condition that affects muscles in the neck, as well as for cosmetic purposes to decrease the appearance of wrinkles. Botox™ and Dysport™ are examples of commercial products. There are also concerns that the botulinum neurotoxin could be weaponised as a biological warfare agent.
An important recent development has been the sequencing of the genome of several strains of C. botulinum, the first of these having been completed by a UK consortium. The availability of genome sequence has permitted whole genome analysis of almost seventy strains, and revealed a number of interesting genetic features, including the neurotoxin gene cluster that has evolved independently of the remainder of the genome.