Clostridium perfringens is a Gram-positive, rod-shaped, non-motile anaerobic, spore-forming bacterium. It produces a highly noxious enterotoxin and is a common cause of food poisoning. The bacteria frequently contaminates  raw protein foods of animal and bird (poultry) origin. It is also found on insects, in soil and dust,  and excreta.

One reason for its growth in high protein substrates is its requirement for more than 12 different amino acids which makes it highly fastidious. Beef products account for 40% of C. perfringens food poisoning (Bhunia, 2008). The bacteria produces an exotoxin (sometimes described as an enterotoxin) in the intestine but is only problematic when infection levels reach 1 million/g vegetative cells in food (Labbe and Juneja, 2006). The enterotoxin stimulates fluid and electrolyte flux from the gastrointestinal tract, hence the diarrheal effects (reviewed – McClane et al.,  1988).

The bacteria is a spore former and readily does so in aerobic conditions whereupon it produces the toxin. The incubation period for this particular bacterium is as little as 2 hours.  The endospore as it is also known is heat resistant which allows it to survive poorly controlled cooking processes. If any meat product is not handled properly or temperature abused then poisoning is likely. The organism is reviewed in the following: McClane, 2003; Novak et al., 2008 but there are many other references in the food safety arena which cover the topic.

Symptoms

The signs of food poisoning are abdominal pain and diarrhoea, nausea and general sickness about 8 to 24 hours after infection. The acid condictions of the stomach are not enough to kill the bacteria. Fortunately the sickness is of short duration and full recovery is made within 48 hours.

The type A strain is most problematic (Bhunia 2008). It is believed to be responsible for 144 thousand cases of gastrointestinal illness a year in the UK, about 250,000 cases in the USA and is the 3^rd ranking cause of such illness in that country (CDC&P, 2011).   The typical growth range is between 15 °C and 52 °C. In its optimum growth range of 43°C -47 °C, it can reproduce every 10 minutes. Having formed spores, these are then reactivated in meats when cooking drives out oxygen. Anaerobic conditions are highly suited to its fermentation (Juneja et al., 1994; Sabah et al., 2004). This is particularly so when meat, gravy and stews are being improperly warmed or cooled slowly. It is particularly prevalent with institutions and large scale caterers or food service providers because of the need to reheat food which can see bacteria activated from spores to grow rapidly.

Control Of Growth

Growth of C. perfringens is cited as a performance standard by  the US authorities when assessing the cooling process for a food (USDA-FSIS 2001; US FDA 2001). The FDA Division of Retail Food Protection (2001) established the guideline that all ready-to-eat (RTE) meat products were to be cooled from 60 to 21 ◦C in 2 h and from 21 to 5 ◦C in 4 h.  The Center for Disease Control and Prevention (CDC&P, 2014) provides a useful resource and other references for consultation on this problematic organism. It is requested that susceptible foods are cooked thoroughly to the recommended temperatures.  The food is then kept at a temperature higher than 60°C or cooler than 5°C. This latter condition prevents germination of spores that survive the initial cooking. The CDC&P also recommends serving food hot immediately after cooking or at least refrigerating it below 5 °C within 2 hours of production.

References

Bhunia, A.K. (2008) Foodborne microbial pathogens-mechanisms and pathogenesis. New York: Springer. p 158–9.
CDC&P.( 2011) Estimates of Foodborne Illness in the United States. Atlanta, GA: Centers for Disease Control and Prevention; 2011 Feb 4. Available from: http://www.cdc.gov/ foodborneburden/2011-foodborne-estimates.html.  Accessed Mar 21^st, 2014.
CDC&P. (2014) Clostridium perfringens. http://www.cdc.gov/foodsafety/clostridium-perfingens.html accessed 21st March 2014.

Juneja, V.K., Snyder, O.P., Cygnarowicz-Provost, M. (1994) Influence of cooling rate on outgrowth of Clostridium perfringens spores in cooked ground beef. J Food Protect. 57 pp. 1063–7.
Labbe, R.J., Juneja, V.K. (2006) Clostridium perfringens gastroenteritis. In: Riemann, H., Cliver, D.O., editors. Foodborne infections and intoxications. San Diego, GA: Academic Press. pp. 137–64.
McClane, B.A. (2003) Clostridium perfringens. In: International Handbook of Foodborne Pathogens. Edt. M.D. Miliotis, J.W. Bier.  Publ. Marcel Dekker, Inc. NY. USA.  Chapt. 6 pp. 91-101
McClane, B.A., Hanna, P.C., Wnek, A.P. (1988) Clostridium perfringens enterotoxin. Microbial Pathogenesis. 4 pp. 317-323

Novak, J.S., Peck, M.W., Juneja, V.K. Johnson, E.A. (2008) Clostridium botulinum and Clostridium perfringens. In: Foodborne pathogens: Microbiology and Molecular Biology.  Edt. Fratamico, P.M., Bhunia, A.K., Smith, J.L. Horizon Scientific Press. Chapt. 19  Pp. 383-407
Sabah, J.R., Juneja, V.K., Fung, D.Y.C. (2004) Effect of spices and organic acids on the growth of Clostridium perfringens during cooling of cooked ground beef. J Food Protect . 67 pp. 1840–7.
US FDA (2001) U.S. Food and Drug Administration, Division of Retailed Food Protection. 2001. Food code. Washington, DC: U.S. Department of Health and Human Services. Public Health Service.
USDA-FSIS. 2001. Performance standards for the production of certain meat and poultry products, final rule. Fed. Regist. 64 pp. 732–49.