If you ever thought you had the 24-hour flu, you may have had a foodborne illness caused by the bacteria Bacillus cereus (B. cereus). Illness from B. cereus is also called “fried rice syndrome” or “reheated rice syndrome” (Leong et al., 2023). Though it has made social media headlines in recent years, B. cereus is not a new microorganism or a new problem.
Key Facts
- B. cereus and its toxin cannot be seen, smelled, or tasted.
- One of the best ways to avoid illness from B. cereus is to refrigerate leftover food promptly.
- It is most often associated with starchy foods like rice.
Different from Spoilage Bacteria
B. cereus is a microorganism that is a bacterium. Like most bacteria that cause foodborne illness (also referred to as food poisoning), it has specific qualities that make it sneaky and dangerous when food is not stored properly.
Spoilage bacteria show signs of their presence in foods through stinky odors, slimy textures, gas production, or mold growth. Bacterium like B. cereus are different because they do not show these signs. Food can look and taste normal yet be contaminated with harmful bacteria or their toxins that cause illness. These illness-causing bacteria are called pathogens.
B. cereus is common in the environment. It can be present in soil and therefore on any food that grows in soil. (U.S. Food and Drug Administration [USFDA], 2012). That means it can become part of a person’s diet with just about any type of food. If people cook their food to the recommended minimum temperatures, the heat will destroy any active B. cereus cells.
Bacteria with Unique Protection
Several types of Bacillus bacteria produce spores (Marrollo, 2016). This means when conditions are not favorable they can build protective armor around themselves and go dormant. This is similar to a seed. A dormant seed has the potential to grow, but it is not actively growing until the environmental conditions are right. B. cereus can remain in the spore form until it encounters optimal growth conditions, which occur in foods at room temperature with plenty of moisture present.
If any B. cereus spores are present in these foods (especially boiled or fried rice, cooked vegetables and meats, pasta, custards, casseroles, and soups) they can grow and multiply as they cool to room temperature for an extended time. Hot and cold foods should stay between temperatures of 40 degrees Fahrenheit to 140 F for no more than 2 hours (USFDA, 2012).
Double Trouble for Sickness
As B. cereus cells grow and multiply, they can produce a toxin in food. Though heat can kill the B. cereus cells, it does not destroy the toxins these cells produce. People may get sick when they ingest this toxin. This sickness happens quickly, within 30 minutes to 6 hours. Symptoms are usually nausea, vomiting, and abdominal cramps. This type of foodborne illness has been associated with starchy foods, including rice, potato, pastas, sauces, puddings, soups, casseroles, and pastries. This is why the term “fried rice syndrome” has been used to describe this type of foodborne illness (Marrollo, 2016).
It is also possible to consume foods containing B. cereus cells and/or spores and for them to produce a toxin in a person’s intestines. In this case it takes 6–15 hours to show symptoms which include diarrhea, cramps, and sometimes nausea. Meats, milk, vegetables, and fish are the foods associated with the diarrheal type of this illness (Marrollo, 2016).
Both types of illness can last approximately 24 hours, leading people to conclude they had the 24-hour flu.
Anyone can get a foodborne illness from eating food contaminated with B. cereus. Symptoms often go away on their own once the bacteria and/or toxin has been expelled from the person’s body. It is possible for some people to have more serious complications. People with a weak or compromised immune system can have a more difficult time fighting the infection.
How Can I Control the Pathogen in My Home?
Proper temperature control can be a problem when preparing large quantities of food and not keeping it warm enough while serving. It can likewise be a challenge for cold food when refrigeration space is in short supply.
- Keep hot foods above 140 F.
- Keep cold foods below 40 F.
- Do not keep hot foods or cold foods at room temperature for more than 2 hours.
One of the best ways to avoid illness from B. cereus is to refrigerate leftover food promptly.
- When cooling hot food, put it in small, shallow containers rather than one large container.
- Slightly prop open any lids or plastic wrap to allow heat to escape until the food is cool.
- Do not stack containers close together in the refrigerator until they are fully cooled.
Practice other ways to handle food safely, including washing your hands, keeping raw and cooked foods separated, and cleaning utensils and surfaces that will touch food.
Additional Resource
- Preventing foodborne illness: Bacillus cereus
(nifa.usda.gov/sites/default/files/resource/Preventing-Foodborne-Illness-Bacillus-cereus.pdf)
References
U.S. Food and Drug Administration. (2012). Bacillus cereus (2nd ed.).
fda.gov/food/foodborne-pathogens/bad-bug-book-second-edition
Leong, S. S., Korel, F., & King, J. H. (2023). Bacillus cereus: A review of "fried rice syndrome" causative agents. Microbial Pathogenesis, 185, 106418.
doi.org/10.1016/j.micpath.2023.106418
Marrollo, R. (2016). Bacillus cereus food-borne disease. In V. Savini (Ed.), The diverse faces of Bacillus cereus (pp. 61–72). Elsevier/Academic Press.
shop.elsevier.com/books/the-diverse-faces-of-bacillus-cereus/savini/978-0-12-801474-5
Originally written November 9, 2011, by Lydia Medeiros and Jeffery LeJeune.