Anaerobic bacteria spoil a wide range of foods including dairy products, meat and poultry products, fresh and canned fruits and vegetables: typically producing gas and putrid odours, with a few of causing illness.
The species of the genus Clostridium most commonly involved in food-borne illness are Clostridium perfringens and C. botulinum.
Intoxication due to C. perfringens is usually brief, self-limiting, and is rarely fatal, says EFSA.
However, the neurotoxins of C. botulinum are among the most toxic naturally-occurring substances and cause severe foodborne illness, sometimes fatal, with symptoms continuing for several months.
Clostridia occur commonly in soil, dust, the aquatic environment and in the intestines of animals, and can consequently be present in a wide range of foods.
C. perfringens is commonly present in foods and ingredients, occasionally at hundreds per gram. C. botulinum is present less frequently, normally at a few spores per kilogramme.
According to the EFSA BIOHAZ panel of scientists, the most essential measures to prevent foodborne diseases caused by C. perfringens are: appropriate cooking, cooling rapidly through the temperature range 55°C to 15°C, holding foods at temperatures between 10°-12°C, and re-heating the product to an internal temperature of 72°C before consumption.
But, they warn: "microbiological testing for C. perfringens has limited value in ensuring food safety, because the organism is so common in or on foods that a positive result means little, unless very high numbers are present.
Moreover, cultural methods detect all C. perfringens, while enterotoxin is produced by only a fraction of strains."
C. botulinum, or botulism as it is frequently known as, is less common. Botulism occurs after ingestion of a neurotoxin formed when spores of C. botulinum type A, B, E or F germinate and multiply in a food.
The EFSA scientists point out that botulism has even occurred after a person, suspecting a food might be spoiled, merely tasted the food after dipping one finger into it.
Theu underline that "toxins of C. botulinum are relatively sensitive to heat and are inactivated by heating at 80°C for 10 min or an equivalent process."
BIOHAZ further underlines that laboratory detection methods for C. botulinum "are not suited to routine food microbiology laboratories" because it is necessary to test for the neurotoxin, and special safety precautions are necessary.
"Hence, testing for C. botulinum and its toxins is not recommended.
Good Hygienic Practices and Good Manufacturing Practices should be built into control of the process, with particular attention paid to the formulation (recipe), the heating process, the storage temperature and the intended duration of storage," suggests the panel.