Common Foodborne Pathogens - IX

Clostridium perfringens Risk Profile 

Clostridium perfringens is an anaerobic and aero-tolerant, gram-positive, spore-forming rod that is relatively cold-tolerant and produces enterotoxins, where its spores are heat-resistant. Nonpathogenic C. perfringens is widely distributed in the environment and is frequently found in the intestines of humans and many domestic and feral animals. The spores persist in soil, sediments, and areas subject to human or animal fecal pollution. Isotype A almost always contains the “cpe” gene or the enterotoxin gene, which causes food poisoning, and types B, C, D, and E sometimes contain this gene among many C. perfringens isotypes found in nature. 
 
Sources 
The actual cause of poisoning happens due to temperature abuse of cooked foods in most instances. C. perfringens can be present in small numbers often after the food is cooked due to germination of its spores, which can survive high heat and can multiply rapidly as a result of a fast doubling time (<10 minutes for vegetative cells), depending on temperature and food matrix. Therefore, during cool-down (109-113°F) and storage of prepared foods, this organism can reach levels that cause food poisoning much more quickly than can other bacteria. Meats (especially beef and poultry), meat-containing products (e.g., gravies and stews), and Mexican foods are important vehicles for C. perfringens foodborne illness, although it is also found on vegetable products, including spices and herbs, and in raw and processed foods. Spores of some C. perfringens strains can survive boiling water for an hour or longer in a relatively protective medium (e.g., a cooked-meat medium, <10 minutes for vegetative cells) depending on temperature and food matrix. Hence, C. perfringens can reach levels that cause food poisoning much more quickly than can other bacteria, during cool-down (109-113°F) and storage of prepared foods.
 

Especially beef and poultry are implicated, other meat varieties and meat-containing products such as gravies and stews, as well as Mexican foods are important vehicles for C. perfringens foodborne infections. C. perfringens is also found on vegetable products, including spices and herbs, and in raw and processed foods, where spores of some C. perfringens strains can survive boiling water for an hour or longer in a relatively protective medium e.g., a cooked-meat medium. 

Growth Factors 

Temperature:

Minimum – 10°C Maximum – 47.1°C Optimum (43 – 47°C)

pH:

Minimum – 5 .0 Maximum – 9.0 Optimum (7.2)

Water Activity (aW):

Minimum – 0.93 Maximum – >0.99 Optimum (0.95 – 0.96)

Water Phase Salt:

Maximum – 7%       

 
Disease 
C. perfringens can cause two types of foodborne infections, and the gastroenteritis form is very common and often is mild and self-limiting. However, it may also develop as more severe gastroenteritis depending on the strain, which leads to damage of the small intestine and, potentially, but rarely, fatality. The second form C. perfringens is enteritis necroticans or “pig-bel disease” or characteristic swollen bellies and other severe symptoms, which is rare in the developed world, but more severe than the other form of the infection, and often fatal. As C. perfringens can replicate much more rapidly than most other bacteria that result in the ingestion of a large number of vegetative cells from both infection forms. Hence, C. perfringens will more quickly reach pathogenic levels in contaminated food left unrefrigerated than other bacteria, and the consumers who eat the food may ingest large doses of the bacterium. 

Mortality 

There were an estimated 26 annual deaths in the United, States according to the Centers for Disease Control and Prevention (CDC) and C. perfringens annually accounts for: 

Common gastroenteritis form - A few deaths resulting from diarrhea-induced dehydration and other complications have been reported, and usually were among debilitated or elderly people. 

Pig-bel form (enteritis necroticans) - This disease is often fatal, and it is extremely rare in the U.S. 

 

Infective dose 

Symptoms are caused by ingestion of large numbers of (> 106) vegetative cells or >106 spores/g of food, where toxin production in the digestive tract (or in vitro) is associated with sporulation, which is characterized as a food infection. 

 

Onset 

Symptoms occur about 16 hours after consumption of foods infected with C. perfringens serotypes that are capable of producing the enterotoxin and containing large numbers of (>106) live vegetative cells or (>106) spores. 

Complications 

Complications are rare in the typical, mild gastroenteritis form of the disease, particularly among people under 30 years of age. However, elderly people are more likely to have prolonged or severe symptoms, as are immunocompromised people. The more severe form of the disease may cause necrosis of the small intestine, peritonitis, and septicemia. 

 

Symptoms 

Gastroenteritis form – Common characteristics include watery diarrhea and mild abdominal cramps. 

Pig-bel form (enteritis necroticans) – Abdominal pain and distention, diarrhea (sometimes bloody), vomiting, and patchy necrosis of the small intestine. 

 

Duration 

The milder form of the disease generally lasts 12 to 24 hours, but symptoms may last 1 to 2 weeks in the elderly or infants. 

 

Route of entry 

Oral. 

 

Pathway 

CPE protein usually is released into the intestines when the vegetative cells lyse on completion of sporulation, where this enterotoxin is responsible for clinical presentation in humans. The enterotoxin induces fluid and electrolyte losses from the GI tract, where the principal target organ for CPE is believed to be the small intestine.

 

Pig-bel disease involves the production of the beta toxin, which is highly trypsin-sensitive, where the effects of low gastrointestinal levels of trypsin appear to have contributed to the progression of the disease. It has been demonstrated that when starvation and high levels of potato consumption which generally contain trypsin inhibitor contributed to low levels of this enzyme in the population. 

 
Frequency 

C. Perfringens poisoning is the second most commonly reported foodborne infection in the U.S, which second only to Salmonella when considering bacterial causes of foodborne infection. The CDC estimates that 965,958 domestically acquired cases occur annually in the United States, where there were 34 outbreaks in 2006 included 1,880 cases excluding isolated cases with an average of 50 to 100 people are affected in one outbreak. Many outbreaks probably go unreported, because the implicated foods and patients’ feces are not tested routinely for C. perfringens or its toxin. 
 
Diagnosis 
C. perfringens poisoning is diagnosed by its symptoms and the typical delayed onset of infection, which is confirmed by detection of the toxin in patients’ feces. The presence of exceptionally large numbers of the bacteria in implicated foods or patients’ fecal samples is also used for bacteriological confirmation. 
 
Target Populations 
Institutional settings, where large quantities of food are prepared several hours before serving such as school cafeterias, hospitals, nursing homes, prisons, etc. are the most common circumstance in which C. perfringens poisoning occurs. The young and elderly are the most frequent victims of C. perfringens poisoning, whereas immunocompromised people are at higher risk of severe infection than are others, such as those with HIV/AIDS or undergoing cancer chemotherapy or immunosuppressive drugs for rheumatoid arthritis or other inflammatory conditions.
 
Food Analysis 

Standard bacteriological culturing methods are applied to determine the C. perfringens in implicated foods and feces of patients, and the serological assays are used for detecting enterotoxin in the feces of patients and for testing the ability of strains to produce toxin. Further identifications are carried out using PCR based methods in modern identification techniques. 

Reference:
FDA Bad Bug Book, Foodborne Pathogenic Microorganisms and Natural Toxins. Second Edition. 2013
Preventive Controls for Human Foods. 2016
www.cdc.gov