Clostridium perfringens is a common soil bacteria that causes a mild case of food poisoning. In this lesson, we will look at one particularly severe outbreak and the factors leading to the higher-than-normal number of deaths that occurred.
Deadly Psychiatric Hospital Outbreak
In 2010, at a psychiatric hospital in Louisiana, several unlikely variables aligned, leading to a severe outbreak of food poisoning caused by Clostridium perfringens. In total, 54 patients and staff developed symptoms and three died. This might not sound too bad. Three out of 54 is only 5.5%.
There are other foodborne illnesses, like typhoid fever for example, with death rates between 15-20%.But, what if I told you that C. perfringens usually only kills less than 0.03% of those infected? Out of 54, only 0.016 of a person would have been expected to die, or, in other words, you could reasonably have expected no deaths due to this outbreak. If you suspect that other factors must have been involved, you would be right.
Like I mentioned earlier, this outbreak was a perfect storm in which several very unlikely situations all occurred at the same time, compounding the illness. In this lesson, we will explore the bacterium Clostridium perfringens using this outbreak as a backdrop to learn why it was so much deadlier than your typical C. perfringens food poisoning outbreak.
Let’s start with the bacterium itself. Clostridium perfringens is a Gram-positive, obligate anaerobic, endospore-forming, rod-shaped bacteria.
Whoa, that’s a mouthful! Let’s look at each term individually. ‘Gram-positive’ refers to the thick layer of peptidoglycan present in the bacterial cell wall, making these cells appear purple in the classic Gram stain.An obligate anaerobe is a bacterium that cannot survive in the presence of oxygen, but since C. perfringens is an endospore-former, it is able to form highly resistant endospores. So, if the cells are exposed to oxygen, they will die, but the endospores will survive. These endospores can also survive drying out, high temperatures and exposure to many common household cleaners.C.
perfringens is commonly found in soil, but small populations are able to survive in the intestines of animals. As a result, the bacteria are also present in sewage. Most people catch C. perfringens by eating meat contaminated with feces containing the bacteria.
C. perfringens grows best in protein-rich, low oxygen environments, like those present in precooked or dried meat and fish. In the case of the psychiatric hospital outbreak, the source of the bacteria was found to be the chicken served at dinner the night before the outbreak.The first of our unique conditions emerges here. The chicken had been cooked the day before it was served and allowed to slowly cool over the next 24 hours. These are the perfect conditions for C.
perfringens. Cooking killed the actively growing bacteria but not the endospores. C. perfringens outbreaks usually occur in large facilities where food is prepared in large batches, like hospitals, prisons and cafeterias. The large amount of food cooked in one pot shields some of the endospores from temperatures high enough to kill them.
After cooking, the chicken was covered and refrigerated in large pans, but the huge bulk of food slowed the cooling. Once the chicken cooled below 140 degrees Fahrenheit, the endospores germinated, and the bacteria multiplied very rapidly. Making matters worse, on three separate occasions, chicken was removed from the pans and allowed to warm up to room temperature, but it was not recooked while employees cut pieces off for sandwiches. This likely led to more contamination and brief bouts of rapid bacterial growth as the food’s temperature temporarily increased.
perfringens Food Poisoning
So, now we have a large batch of chicken full of actively growing bacteria as a result of being poorly handled and prepared. Let’s take a quick look at what the bacteria do to the body. First of all, a patient must consume a massive amount of C. perfringens cells before symptoms will develop, upwards of 100 million cells.Your gastrointestinal tract is not a favorable environment for C.
perfringens growth, so the bacteria form endospores to ride out the poor growth conditions. This is where the problems start. During the sporulation process, C. perfringens releases an enterotoxin into your intestine.An enterotoxin is a toxin that is active in the gastrointestinal tract of a host. The enterotoxin makes the intestinal lining much more permeable to water, resulting in an increased flow of water into the intestine.
What results is Clostridium perfringens food poisoning. Remember, in food poisoning, the symptoms are a result of preformed microbial toxins, in this case C. perfringens enterotoxin, not actively growing bacteria.Within 8-12 hours, a patient will start experiencing diarrhea and abdominal cramping. The symptoms usually resolve without treatment in about 24 hours.
In very young and very old patients, the diarrhea can be more severe, lasting 1-2 weeks, and these patients can die from dehydration complications. But, even in high-risk patients, fatalities are very rare.At this point, several more compounding factors are revealed in the Louisiana outbreak. Since this outbreak occurred in a hospital, many of the patients were older and on medication – therefore, they were already at higher risk for complications.
It turns out all three patients that died were older adults on medications that slowed the gastrointestinal tract. Now we have a deadly combination of an enterotoxin that causes increased water in the intestines and abnormally slow movement through the gut.This puts the enterotoxin in contact with the intestinal cells longer than normal, resulting in more and more water flowing into the intestine. The water and fecal material was not moved out fast enough, creating a backlog of waste in the intestine. Dehydration and intestinal cell death from the overfilled bowel contributed to the deaths of these patients.
Diagnosis and Treatment
C. perfringens was diagnosed as the causative agent in this outbreak by examining the feces of those showing symptoms.
Diagnosis usually follows two pathways when C. perfringens is suspected. First, there are tests available that detect the enterotoxin in the feces. This is most often all that is required.
For additional verification, the polymerase chain reaction can also be used to identify the bacteria down to the individual strain by examining the DNA. Both methods were used in Louisiana.Once confirmed to be C. perfringens, treatment usually involves nothing more than drinking plenty of fluids and getting rest. Antitoxins are available but only used in the most severe cases.
It is worthwhile to mention that antibiotics are not effective against C. perfringens food poisoning. The symptoms are a result of the enterotoxin, not the bacteria itself, making antibiotics useless.
So, what could the hospital staff have done differently to prevent this outbreak? First of all, all protein-rich foods should be thoroughly cooked to 165 degrees Fahrenheit before serving.
Meals prepared for a large group should be frequently stirred or broken up into smaller quantities to ensure even heating and to prevent any endospores from surviving.Before serving the food, the temperature should never drop below 140 degrees Fahrenheit. Any leftovers need to be split into small quantities and refrigerated immediately so they cool rapidly and prevent growth of C. perfringens. The staff in Louisiana failed to follow any of these precautions, with disastrous results.
There are about a million cases of C. perfringens food poisoning in the United States every year, and it is not just people in large facilities that get it. Anyone can get food poisoning, so it is a good idea to follow these same instructions. Thoroughly cook your food and promptly refrigerate leftovers to prevent most C. perfringens cases.
To recap, Clostridium perfringens is a Gram-positive, obligate anaerobic, spore-forming, rod-shaped bacteria commonly found in soil and the intestines of animals.
Protein-rich foods, like meat and fish, can harbor the bacteria. If a person consumes a large enough number of bacterial cells, they can get food poisoning. Once in the intestine, C. perfringens forms endospores.This process releases an enterotoxin, which is a toxin that is active in the gastrointestinal tract of a host.
The enterotoxin causes a massive flow of water into the intestine, resulting in abdominal cramps and diarrhea. The symptoms are a result of the toxin, not the C. perfringens cells, making this an example of food poisoning.The symptoms usually resolve in a day or so. Treatment includes getting plenty of rest and drinking plenty of fluids.
On rare occasions, such as cases involving the very young and very old, antitoxins may be required. Deaths are very rare from C. perfringens food poisoning and almost always involve the very young or very old.
Following this lesson, you’ll be able to:
- Describe the structure of Clostridium perfringens
- Explain how food poisoning from C.
- Summarize the treatment of C. perfringens food poisoning in high-risk populations
- Identify the factors that led to the severe outbreak of C. perfringens food poisoning at a Louisiana hospital in 2010