Microbe of the Month – C.perfringens

The following is from The Bug Bible - http://www.safefood.net.au/AudienceHierarchy/TheBugBible/Default.htm

As early as 1895, Clostridium perfringens was associated with human diarrhoea, although it wasn't until the 1940s that it was confirmed to be a cause of food poisoning. C. perfringens is widely found in soil and is a minor component of the flora of the intestinal tracts of humans and animals.

The more common form of illness caused by this organism is of short duration and is characterised by diarrhoea and severe stomach cramps caused by an enterotoxin released in the gut.

The infective dose is large and therefore growth must occur in the food prior to ingestion. In other words, low numbers of the organism are not likely to bring on any illness.

This organism is an anaerobe. It requires a reduced level of oxygen for growth and it produces a spore, an entity which allows the organism to survive most normal cooking temperatures. The organism grows well at warm temperatures with an optimum temperature of 430-45ºC.

At cold temperatures <10ºC, the organism does not grow and while the cell may die off, the spore will survive.

The cells and spores of this organism are likely to be present in many foods of animal origin while the spores can be present in spices, seeds and vegetables. Many cooking techniques such as braising will not destroy the spores. It is important that soups casseroles and large joints of meat are consumed immediately after cooking or rapidly cooled and stored below 10ºC.

These foods must not be allowed to cool at ambient temperatures because rapid growth of clostridia will occur in the 40-50ºC range.

C. perfringens is ubiquitous in the environment and will be present in the kitchen. Control is achieved by:

  • personal hygiene - the organism is part of the normal human gut flora
  • correct cooking temperatures
  • rapid cooling and storage below 10ºC for bulk foods eg soups, casseroles etc

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