Final answer:
A swollen can indicates botulism, caused by the bacterium Clostridium botulinum, which grows in anaerobic conditions in improperly canned foods.
Step-by-step explanation:
A swollen can is a sign of botulism, which is a potentially fatal illness caused by the toxin produced by the anaerobic bacterium Clostridium botulinum. Botulism can occur in improperly sterilized canned foods because the lack of oxygen creates an environment suitable for the growth of C. botulinum. Symptoms of botulism include paralysis and respiratory failure. Proper sterilization and canning procedures are necessary to prevent this illness, as the spores of C. botulinum can survive boiling temperatures and can only be destroyed through high-pressure canning methods.
Public health officials have witnessed cases where home-canned foods like potatoes were not canned correctly using high-pressure methods, leading to botulism outbreaks. It is essential for home canners to follow recommended guidelines to prevent the development of these harmful bacteria in preserved foods.