Clostridium perfringens

Clostridium perfringens

Clostridium perfringens (C. perfringens) is a gram-positive, rod-shaped, anaerobic and spore-forming bacterium and was initially identified as a cause of food poisoning in the 1940s and has become one of the most common foodborne diseases found in industrialized countries.

Due to the anaerobic nature of the bacteria, it prefers to grow in conditions with very little to no oxygen. Food poisoning by C. perfringens is due to the ingestion of the bacterium in large quantities or the spores which then sporulates in the intestines and produces an enterotoxin (Type A is specifically the one that causes the foodborne illness) and once it is in the intestine it acts specifically on the small intestine.

Sources of contamination

Like many spore-forming bacteria, the spores are very resilient and are resistant to high temperatures (up to 100 degrees Celsius) meaning the normal cooking process of food will often not kill the spores and due to the lack of oxygen during cooking in some processes, these factors can allow for the spores to grow and release the toxin. C. perfringens has an optimum growth temperature of ±45 degrees Celsius but can grow in temperatures ranging from 12 degrees Celsius to 60 degrees Celsius. It is not uncommon for C. perfringens to be present in raw meats, poultry, dehydrated soups and sauces, raw vegetables, and spices.

Typical or common food sources:

  • Raw meats
  • Poultry
  • Gravies / Sauces
  • Spices
  • Raw vegetables
  • Dried / Pre-cooked foods

How do we test for C.perfringens in our SANAS accredited laboratory

At FCS we test for Clostridium perfringens by preparing a sample (powder, solid or liquid) and spreading it over a selective agar called Perfringens agar. Once the sample has dried and the second layer of perfringens agar is added to sufficiently cover the first layer. The petri dish or plate is then placed in an anaerobic jar with anaero-test strip and anaero-cult A block(s) (to ensure anaerobic conditions) and placed in an incubator set to ±37 degrees Celsius and incubated anaerobically for 18 to 22 hours.

Presumptive C. perfringens colonies (black in colour and found between the layers of agar) are then taken and inoculated into tubes with thioglycolate media and topped with a thin layer of paraffin to maintain anaerobic conditions and incubated at ±37 degrees Celsius for another 18-24 hours. After this second round of incubation, a small amount of the thioglycollate media is transferred into tubes with Lactose sulphite medium (supplemented) and placed into a water bath set at ±46 degrees Celsius for 18 to 24 hours to incubate again. A positive presence of C. perfringens is confirmed when a black precipitate and gas production is noted in the tube after this last incubation period.

Symptoms of food poisoning

Typical or common symptoms of C. perfringens food poisoning:

  • Diarrhoea
  • Abdominal cramps
  • Fever / Nausea (very rare)

Symptoms can occur within 6 to 24 hours (typically 8 to 12 hours), they have a sudden onset and last for less than 24 hours.

Preventing C.perfringens food poisoning

Key aspects of preventing C.perfringens food poisoning are:

  • Foods especially meats (roasts of beef or poultry) should be cooked to a safe internal temperature and kept at 60 degrees Celsius or higher or at 4 degrees Celsius or cooler after cooking.
  • Meat dishes should be served hot (60 degrees Celsius or above) and within 2 hours after cooking.
  • Leftovers should be reheated to at least 74 degrees Celsius before serving.
  • Ensuring that when shopping all meat products are bagged and packed separately from other products.
  • Store meat products in refrigeration units as soon as possible and not left out at ambient temperatures for extended periods of time.
  • Prepare foods safely by ensuring all equipment is properly cleaned before and during use and that personal hygiene practices (washing of hands) is conducted before, during and after food preparation.

Food Consulting Services is a private South African-owned Food Testing Laboratory and Food Safety Consultancy, that tests water and food to ensure compliance with South African National Standards. We also perform hygiene survey audits to the hospitality and food manufacturing industry. If you’d like to learn more about Food Consulting Services, visit our website or feel free to enquire with us. We look forward to hearing from you and becoming your food safety partners. Get in touch with us for more information.

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