Foodborne Pathogens Questions and Answers

Answer: B

The Gram positive pathogen is Clostridium botulinum.

C. botulinum is a Gram positive, anaerobic, spore-forming rod. Its neurotoxin causes botulism, and its heat-resistant spores are the reason low-acid canned foods receive a full sterilizing process.

The other three are Gram negative: Campylobacter jejuni is a curved rod and a leading cause of bacterial gastroenteritis; Vibrio cholerae is a comma-shaped rod causing cholera; Salmonella typhi is the rod that causes typhoid fever.

Answer: D

Ergotism is caused by grains infected with Claviceps purpurea.

This fungus infects the flowers of rye and other cereals and replaces the grain with a hard, dark sclerotium, the ergot. Ergot contains alkaloids such as ergotamine that constrict blood vessels and act on the nervous system, causing gangrene of the limbs or convulsions and hallucinations (the medieval 'St Anthony's fire').

Clostridium perfringens is a bacterium that causes food poisoning through an enterotoxin, Rhizopus stolonifer is bread mould, and Lactococcus lactis is a harmless lactic acid bacterium used in cheese making.

Answer: C

Ergot poisoning is caused by Claviceps purpurea (printed in the paper as 'Clavis purpurea').

Claviceps purpurea is a fungus that infects the flowers of rye, wheat and other grasses and replaces the grains with dark, hard sclerotia called ergots. These contain ergot alkaloids, and eating flour made from contaminated grain causes ergotism, with convulsions or gangrene of the limbs.

The other organisms cause different illnesses. Bacillus cereus causes vomiting and diarrhoeal food poisoning, Aspergillus flavus produces aflatoxins, and E. coli causes infections such as traveller's diarrhoea. None of them produces ergot.