Clostridium Bacteria in Foodborne Illness and Multiple Sclerosis
An Interesting and Sometimes Dangerous Bacterium
Clostridium perfringens is a microscopic bacterium that can have major effects on humans. It exists in different forms called strains. Depending on the strain, the bacterium can live peacefully in our gut, produce a nasty case of foodborne illness, cause gas gangrene or perhaps cause multiple sclerosis.
The CDC (Centers for Disease Control and Prevention) says that C. perfringens is one of the most common causes of foodborne illness in the United States. Nearly a million cases are reported every year. The bacterium reproduces rapidly in a suitable environment.
Multiple sclerosis or MS is a disease in which the fatty insulation around nerve cells in the brain and spinal cord is destroyed. The insulation is made of a substance called myelin and is often known as the myelin sheath. Without this sheath, nerves are unable to conduct nerve impulses correctly. Patches of scar tissue called lesions develop where the myelin is destroyed. Oligodendrocytes, the cells that make the myelin sheath, are also destroyed. Recent discoveries suggest that a Clostridium perfringens toxin called epsilon may cause these effects.
Clostridium perfringens is a rod-shaped bacterium that produces spores in order to reproduce. The bacterium is nonmotile and often exists in pairs or short chains. It's an anaerobic organism, which means that it requires an environment without oxygen.
Clostridium perfringens can cause very unpleasant effects, depending on the strain of the bacterium and its abundance. A small population of C. perfringens lives in the intestine of some people as part of their normal microbe community.
We all have bacteria and other microorganisms in our intestine. Most of these organisms are believed to be helpful. Harmful microbes are normally present at a low level and don't seem to hurt us. If their population increases, however, we may experience health problems.
C. perfringens is found in animal intestines as well as human ones. It enters food sources such as meats, stews, soups and gravies, which are the most common sources of human infections. In addition, it's found in soil as a contaminant deposited by animal feces.
Foodborne Illness or Food Poisoning
Clostrium perfringens sometimes has no effect when it's ingested. When a large number of bacterial cells are eaten, however, illness often results.
The bacteria are generally found in raw meat and poultry products. Their spores can survive at high temperatures, including those used in cooking. If cooked food is held at room temperature before being served, the spores will germinate, producing new bacterial cells that in turn produce toxin.
Outbreaks of food poisoning most often happen in institutions such as hospitals, prisons and school cafeterias because food in these places isn't served immediately after cooking. Food poisoning may also arise at events involving catered food.
The chief symptoms of poisoning by C. perfringens are abdominal cramps and diarrhea. The symptoms can be bad in anyone, but they are generally worse in children and elderly people.
The symptoms don't begin immediately after eating contaminated food. They commonly appear eight to twelve hours after ingestion and last for as long as twenty-four hours. In susceptible people the symptoms may last for a lot longer, however. Diarrhea is sometimes so bad that fluid replacement with electrolytes is needed.
Preventing Foodborne Illness
The CDC says that to avoid the growth of Clostridium perfringens spores, cooked meat dishes should be held at a temperature that is greater than 140°F (60°C) or less than 41°F (5°C) if they aren't being served very soon. Leftovers should be heated to at least 165°F (74°C). These temperatures should prevent spores from germinating. If the spores germinate, the new cells will reproduce and quickly form a large population of dangerous bacteria.
It's important to realize that it may not be possible to identify contaminated food by inspection. The appearance, odor and taste of the food may be normal. This is one reason why it's so important to keep food under safe conditions.
The link between C. perfringens and foodborne illness is confirmed and well known. The possible link between the bacterium and multiple sclerosis is very intriguing but is more tentative.
What is Multiple Sclerosis?
Symptoms of multiple sclerosis vary greatly and depend on the part of the central nervous system (brain and spinal cord) where the lesions are located. Not all patients experience all of the symptoms listed below, and some experience different symptoms from the most common ones. The seriousness of the symptoms also varies.
The most common symptoms of MS include the following.
- burning sensations
- balance problems
- muscle weakness
- muscle spasticity (stiffness)
- speech, vision, bladder or bowel problems
A person with MS may also experience memory and thinking problems. These symptoms are usually mild, however.
Although multiple sclerosis may lead to disability (but doesn't always do so), lifespan of an MS patient is the same as or only slightly less than that of a person without MS.
Coping with a Multiple Sclerosis Diagnosis
Types of Multiple Sclerosis
Multiple sclerosis is classified into four types.
- In Relapsing Remitting MS, or RRMS, periods when symptoms appear alternate with periods when they're absent or greatly reduced. The duration of the flare-ups and the remissions varies. About 85% to 90% of MS patients have this type of the disease.
- In Primary Progressive MS, or PPMS, the symptoms of the disease gradually get worse over time once they start. The disease may stabilize or even improve slightly for short periods, but the overall trend is for the symptoms to worsen. It's estimated that about 10% to 15% of people with MS have this form of the disease.
- Secondary Progressive MS or SPMS generally follows Relaxing Remitting MS that has existed for many years. Symptoms worsen over time and there are no remissions.
- Progressive Relapsing MS, or PRMS, is a rare form of the disease. It's similar to Relaxing Remitting MS, except the disease progresses and the symptoms gradually get worse.
Possible Causes of the Disease
The cause of multiple sclerosis is unknown. Many different ideas have arisen over the years, but none of them have been proved. This is very frustrating for MS patients and their families. A definitive cause could pave the way for an effective treatment and perhaps even a cure for the disease.
Many investigators think that the cause of MS is a combination of environmental and genetic factors. Research has shown an association between multiple sclerosis and infection by the Epstein-Barr virus, smoking and a lack of vitamin D manufacture in the skin due to insufficient sunlight in the environment. These factors may cause MS only in people with a specific genetic makeup, however. Some researchers think the factors don't cause MS but worsen the disease once it has begun. Obesity is also believed to make multiple sclerosis worse.
Another common theory is that multiple sclerosis is an autoimmune disease. The immune system's purpose to to destroy microbes and dangerous molecules that enter the body. In an autoimmune disease, for an unknown reason the body's immune system attacks and destroys its own tissues. As the neurologist in the video below says, however, some aspects of MS indicate that it's an autoimmune condition while others don't. The immune system may be involved in just the initiation of the disease or in just the progression of the disease.
An Overview of Multiple Sclerosis by a Mayo Clinic Neurologist
In the central nervous system or CNS, oligodendrocytes wrap layers of their cell membrane around nerve cells (neurons) to form the myelin sheath. In the peripheral nervous system, Schwann cells do the same job. In multiple sclerosis, the myelin sheath and oligodendrocytes in the CNS are damaged and destroyed.
Clostridium perfringens and MS - A Possible Link
The latest discoveries about the relationship between bacteria and MS is very interesting and is hopefully very significant. If a bacterial toxin is proven to be a cause of multiple sclerosis, it may be possible to create new treatments for the disease which may help at least some patients. Scientists use the results of both animal and human investigations to support their claim that some strains of C. perfringens can cause multiple sclerosis.
There are five strains of Clostridium perfringens. They are identified by the first five letters of the alphabet. The toxin known as epsilon is made by types B and D of the bacterium.
Clostridium perfringens and Epsilon in Humans and Animals
In 2013, researchers at the Weill Cornell Medical College made some interesting discoveries in relation to C. perfringens, epsilon and MS.
- The researchers found both Clostridium perfringens type B and epsilon in a multiple sclerosis patient who had "actively enhancing " lesions. This was the first discovery of the type B bacterium in humans.
- The scientists also found that Clostridium perfringens type A was present in 50% of the people without MS who were surveyed and only 23% of the people with MS. The type A strain of the bacterium hasn't been linked to MS and is often a normal gut inhabitant.
- In addition, the researchers discovered that 10% of blood serum or spinal fluid samples taken from people with MS contained antibodies for epsilon while only 1% of the fluids from people without multiple sclerosis contained the antibodies. This indicates that the immune system of the people with MS had received prior exposure to the toxin.
In 2014, the same researchers that made the above discoveries reported that mice given epsilon developed brain damage similar to that which occurs in human MS patients. Other researchers have shown that epsilon causes MS-like symptoms in ruminant animals. In 2015, scientists reported that epsilon binds to the myelin of Chinese hamster nerve cells. Other researchers discovered that in lab equipment epsilon binds to mouse oligodendrocytes and kills them.
The Blood-Brain Barrier
Many substances are unable to cross the blood-brain barrier, which means that they can't leave blood capillaries to enter the brain. Some substances can cross the barrier, however. They enter the brain by the techniques mentioned in the diagram above.
Epsilon, the Blood-Brain Barrier and the Nervous System
The human and mouse brain is protected by capillaries that form the blood-brain barrier. Unlike other capillaries, those in the blood-brain barrier contain tightly packed cells that prevent the passage of many types of molecules into the brain. Epsilon is able to cross the barrier, however.
Researchers think that epsilon not only crosses the blood-brain barrier but also binds to receptors on the myelin sheath around nerves and on the body of the oligodendrocytes. The presence of the epsilon may lead to the destruction of myelin and the death of the oligodendrocytes. Further research is needed in order to determine whether this scenario actually occurs in the human body, and if it does, to reveal more details about the process.
Significance of the Epsilon Discoveries
The history of research into the causes of MS involves a disappointing pattern. Researchers announce that they've discovered a cause of the disease, people become excited and then other researchers are unable to confirm the results of the experiment or survey. This pattern doesn't mean that the original researchers were dishonest. Human biology is very complex and research in this area is fraught with difficulty.
Nevertheless, the latest research is extremely interesting. C. perfringens type B is considered to be a very rare bacterial strain in humans. It does occur in cows and sheep and causes disease in these animals. It's possible that the type B bacterium or the epsilon that it produces is not as rare in humans as thought. Much more research involving many more human subjects needs to be performed to confirm the effect of C. perfringens on MS, however.
Even if epsilon can cause multiple sclerosis, it may do so only in a subset of patients. The discovery may still be very meaningful, however. It may help patients or potential patients by leading to new disease treatments or a vaccine. It may also help scientists to learn more about multiple sclerosis, a potentially debilitating and very frustrating disease.
References and Further Reading
© 2014 Linda Crampton
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