Food poisoning 101: 3 spore-forming bacteria that cause foodborne illness

The Centers for Disease Control and Prevention (CDC) estimates that each year roughly 1 in 6 Americans (or 48 million people) get sick, 128,000 are hospitalized, and 3,000 die of foodborne diseases.

Clostridium perfringens gram stain
Image/CDC

At least three bacterium capable of forming spores are known causes of foodborne illness- Bacillus cereus, Clostridium perfringens and Clostridium botulinum.

These bacterium, in general, are found in foods grown in the soil like vegetables and spices. They are aloso found in meat. The spores itself are not harmful when eaten, with the exception of C. botulinum spores in the case of infant botulism.

The spore-forming bacteria are an issue in food establishments that do not cool foods properly.

1. Bacillus cereus

Bacillus cereus is a well recognized and common cause of food poisoning (bacterial intoxication or toxin-mediated infection) worldwide.  It is commonly found in low levels in raw, dried and processed foods.  The bacterium causes two types of toxins: a diarrheal type and a vomiting type.

The diarrheal type of this food poisoning is usually associated with meats, milk and vegetables. The onset for the disease is from 8-16 hours and it lasts 12 to 14 hours.

The vomiting type of this food poisoning is due to rice, grains, cereals and other starchy foods. The onset is quite rapid (30 minutes to 6 hours) and usually lasts a day or so. This type is frequently associated with outbreaks due to cooked rice held at room temperature.

This type of food poisoning is rarely fatal and cannot be transmitted from person to person.

Prevention is properly cooking of food, and if not consumed, rapid cooling prior to storage.

2. Clostridium perfringens

Clostridium perfingens intoxication is due to a toxin mediated infection where the ingested bacteria colonize in the intestinal tract and subsequently produce their toxin.

Although Clostridium perfringens is an organism most frequently associated with gas gangrene, it is also a major cause of food poisoning

Almost all outbreaks are associated with inadequately heated or reheated meats, usually stews, meat pies, and gravies made from beef, turkey or chicken.

Outbreaks of Clostridium perfringens food poisoning are usually traced to catering firms, restaurants, cafeterias and schools with inadequate cooling and refrigeration facilities for large-scale service.

After a period of 8 to 22 hours, this intestinal disease is characterized by a sudden onset of colic followed by diarrhea and nausea. Vomiting and fever are not usually present.

It is generally a mild disease lasting about 24 hours or less. It is rarely fatal in otherwise healthy people.

However, there is a more severe disease caused a different strain of C. perfringens (type C strains). This disease can cause necrotic enteritis which is frequently fatal. Also known as pig-bel syndrome, this strain can cause necrosis of the intestine and can go septic.

In order to prevent getting Clostridium perfringens food poisoning the following steps should be taken:

• Serve meat dishes hot or cool them by refrigerating till serving.
• Large cuts of meat must be thoroughly cooked.
• For more rapid cooling of large dishes like stews, divide the stew into several smaller, shallower containers and refrigerate.

3. Clostridium botulinum

Food borne botulism is a severe intoxication caused by eating the preformed toxin present in contaminated food.

Botulism is often associated with home-canning
Image/CDC

Food borne botulism occurs when the bacterium Clostridium botulinum is allowed to grow and produce toxin in food that is later eaten without sufficient heating or cooking to inactivate the toxin. Botulinum toxin is one of the most potent neurotoxins known.

Growth of this anaerobic bacteria and the formation of the toxin tend to happen in products with low acidity and oxygen content and low salt and sugar content. Inadequately processed, home-canned foods like asparagus, green beans, beets, and corn have commonly been implicated.

However, there have been outbreaks of botulism from more unusual sources such as chopped garlic in oil, chili peppers, improperly handled baked potatoes wrapped in aluminum foil and home-canned or fermented fish. Garden foods like tomatoes, which used to be considered too acidic for the growth of Clostridium botulinum, is now considered a potentially hazardous food in home canning.

Though more common in home-canned foods, it does happen occasionally in commercially prepared foods.

Typically in a few hours to several days after you eat the contaminated food you will start to show the classic symptoms; blurred vision, dry mouth, and difficulty in swallowing. Gastrointestinal symptoms may or may not occur. If untreated, the paralysis always descends through the body starting at the shoulders and working its way down.

The most serious complication of botulism is respiratory failure where it is fatal in up to 10% of people. It may take months before recovery is complete.

If the disease is caught early enough it can be treated with antitoxin. If paralysis and respiratory failure happen, the person may be on a ventilator for several weeks.

Prevention of botulism is by properly heat processing anaerobically packed foods. For more infectious disease news and information, visit and “like” the Infectious Disease News Facebook page