David Dinsmore of the Town Talk of Alexandria and Pineville Louisiana continues to report on the tragedy surrounding an outbreak of illnesses that sickened more than 40 people and killed three patients at Central Louisiana State Hospital. Mr. Dinsmore reports that test results found the third most common cause of food poisoning — clostridium perfringens — was to blame for the outbreak at Central earlier this month, said Dr. David Holcombe, medical director for Region 6 of the Louisiana Department of Health and Hospitals’ Office of Public Health. The C. perfringens bacterium appears to have come from the chicken salad served before patients and staff members began getting sick, Holcombe said. Those who had the chicken salad at that time were 23 times more likely to show symptoms, which is a good indicator that the dish was the culprit.
Clostridium perfringens is an anaerobic, Gram-positive, sporeforming rod (anaerobic means unable to grow in the presence of free oxygen). It is widely distributed in the environment and frequently occurs in the intestines of humans and many domestic and feral animals. Spores of the organism persist in soil, sediments, and areas subject to human or animal fecal pollution. (1)
Perfringens food poisoning is the term used to describe the common foodborne illness caused by C. perfringens. The symptoms are caused by ingestion of large numbers of (greater than 10 to the 8th) vegetative cells. Toxin production in the digestive tract (or in test tubes) is associated with sporulation.
The common form of perfringens poisoning is characterized by intense abdominal cramps and diarrhea which begin 8-22 hours after consumption of foods containing large numbers of C. perfringens bacteria capable of producing the food poisoning toxin. The illness is usually over within 24 hours but less severe symptoms may persist in some individuals for 1 or 2 weeks. In the elderly or infirm, those symptoms may often last 1-2 weeks. Complications and/or death only very rarely occur; a few deaths have been reported as a result of dehydration and other complications.
Perfringens poisoning is diagnosed by its symptoms and the typical delayed onset of illness. Diagnosis is confirmed by detecting the toxin in the feces of patients. Bacteriological confirmation can also be done by finding exceptionally large numbers of the causative bacteria in implicated foods or in the feces of patients. Standard bacteriological culturing procedures are used to detect the organism in implicated foods and in feces of patients. Serological assays are used for detecting enterotoxin in the feces of patients and for testing the ability of strains to produce toxin. The procedures take 1-3 days. (1)
Spores of foodborne bacterial pathogens such as Clostridium perfringens are very heat-resistant. Many spores are activated by heat, and may germinate and grow if the process of cooling food to < 5 degrees Centigrade. Cooling processes must be designed to minimize growth of sporeforming foodborne pathogens. The USDA’s draft compliance guidelines for RTE meat and poultry products state that during cooling there should be no more than 1 log10 growth of Clostridium perfringens throughout the meat. (2)
In most instances, the actual cause of poisoning by C. perfringens is temperature abuse of prepared foods. Small numbers of the organisms are often present after cooking and multiply to food poisoning levels during cool down and storage of prepared foods. Meats, meat products, and gravy are the foods most frequently implicated. Institutional feeding (such as school cafeterias, hospitals, nursing homes, prisons, etc.) where large quantities of food are prepared several hours before serving is the most common circumstance in which perfringens poisoning occurs. (1)
Spores may germinate during heating, and the resultant cells can multiply at high levels if food containing the cells is (1) hot-held for extended periods at insufficiently hot temperatures, (2) improperly cooled, or (3) improperly stored. “Improper holding temperature” was cited as a contributing factor in 69 of 74 outbreaks for which at least one contributing factor was reported. (3)
Perfringens poisoning is one of the most commonly reported foodborne illnesses in the U.S. There were 1,162 cases in 1981, in 28 separate outbreaks. At least 10-20 outbreaks have been reported annually in the U.S. for the past 2 decades. Typically, dozens or even hundreds of person are affected. It is probable that many outbreaks go unreported because the implicated foods or patient feces are not tested routinely for C. perfringens or its toxin. CDC estimates that about 10,000 actual cases occur annually in the U.S. (1)
(1) “Clostridium perfringens”, Foodborne Pathogenic Microorganisms and Natural Toxins Handbook, US Food and Drug Administration.
(2) E. Doyle, PhD, “Survival and Growth of Clostridium perfringens during the Cooling Step of Thermal Processing of Meat Products”, Food Research Institute, February 2002.
(3) E. Crouch; N, Golden, “A Risk Assessment for Clostridium perfringens in Ready-To-Eat and Partially Cooked Meat and Poultry Products”, USDA, Food Safety Inspection Service, September 2005.