Description
Clostridium perfringens are Gram-positive, anaerobic sporeforming rods. They are widely distributed in the environment and frequently occurs in the intestines of humans and many domestic and feral animals. The spores are capable of surviving in soil, sediments and areas subject to faecal contamination. The spores are also extremely heat resistant and have been reported to survive boiling for several hours. C. perfringens can grow at temperatures ranging from 15 to 50°C, and pH values of between 5.0 and 8.0.
Nature of acute disease
The illness caused by C. perfringens is sometimes referred to as Perfringens food poisoning. The illness is caused by toxin being produced in the stomach by large numbers of the microorganisms. A more serious but rare illness is also caused by a certain strains of C. perfringens, Type C strain. This is known as enteritis necroticans and is rare in Australia. Pig-bel, a milder form of necroticans, is associated with the highland people of New Guinea.
Characteristics of Illness
Symptoms: Food poisoning caused by C. perfringens is characterised by intense abdominal cramps and diarrhoea.
Onset of Symptoms: 8-22 hours after consumption of foods containing large numbers of C. perfringens.
Duration of Illness: The illness is usually over within 24 hours but less severe symptoms may persist in some individuals for 1 or 2 weeks.
Infective Dose: At least 106 vegetative cells per gram of food are required before illness can occur.
Diagnosis of human illness
The illness is diagnosed by examining the symptoms of the patient and the onset times. It is usually confirmed by detecting large numbers, greater than 105 cells per gram, of the bacteria in the faeces of the patient and in the implicated food.
Complications
The disease generally lasts 24 hours. In the elderly or infirm, symptoms may last 1-2 weeks. Complications and/or death only occur very rarely. A few deaths have been reported as a result of dehydration and other complications. Necrotic enteritis caused by C. perfringens type C is often fatal. It is a result of ingesting large numbers of the causative bacteria in contaminated foods. Death is usually caused by infection and necrosis of the intestines and from resulting septicaemia.
Susceptible individuals
The young and elderly are the most frequently affected, with elderly persons most likely to experience prolonged or severe symptoms. Except in the case of pig-bel syndrome, complications are few in persons under 30 years of age.
Associated foods
Institutional feeding (such as school cafeterias, hospitals, nursing homes, prisons, etc.) where large quantities of food are prepared several hours or the day before serving has been the most common situations where C. perfringens food poisoning occurs. But, any situation where large volumes of food are prepared then stored before consumption pose a risk. The most common cause of C. perfringens food poisoning is temperature abuse of prepared foods. Small numbers of the organisms or their spores are often present after cooking. After cooking the spores germinate and the cells multiply to levels capable of causing food poisoning during cooling of foods and warm storage. Meats, meat products, casseroles and gravy are the foods most frequently implicated, but any food cooled to slowly could pose a hazard.
Further Information
Websites:
Communicable Diseases - Australia
FDA Bad Bug Book
Literature:
Hocking, A.D. et al. (1997). Foodborne Microorganisms of Public Health Significance. 5th ed. North Sydney. AIFST NSW Branch Food Microbiology Group.
Doyle, M.P. (1989). Foodborne Bacterial Pathogens. Marcel Dekker; New York.