What Is Bacillus Cereus? The Bacteria Behind Common Food Poisoning
Updated: 3 days ago
Medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: October 2026
Quick Answer
Bacillus cereus is a common bacterium in soil, dust and water that causes food poisoning when food is improperly cooked or stored, releasing toxins that cause cramps, nausea, vomiting and diarrhea. [1] [5] Rice, pasta and many other foods can carry it. [1] [5] Most cases resolve within a few hours to two days with rest and fluids. [1] [5] Seek care for severe dehydration. [1] [5]
Key takeaways
Bacillus cereus is a bacteria in soil, dust, and water that most often causes food poisoning. [1] [5]
Symptoms include abdominal pain or cramping, nausea, vomiting, and watery diarrhea. [5]
It comes from improperly cooked or stored foods: rice, meats, sauces, dairy, fish, soups, stews, sushi, and starchy foods. [1]
Reheating or frying food doesn't always kill the bacteria or remove its toxins. [1] [5]
Illness usually clears on its own within a few hours to two days with rest and fluids; antibiotics usually won't help. [1] [5]
Complications are rare but can include dehydration and, rarely, infections of the eyes, lungs, skin, or brain in people with weakened immune systems. [1]
Prevention: cook to safe internal temperatures, refrigerate leftovers within two hours, keep cold food at or below 38°F (4°C), and discard food left out too long. [1]
What the research says
Fried rice syndrome is a recognized pattern of B. cereus illness, driven by two kinds of toxin. A review of outbreak cases reported between 1984 and 2019 describes a self-limiting diarrheal illness caused by heat-resistant enterotoxin proteins and an emetic (vomiting) illness caused by a toxin called cereulide. It highlights B. cereus contamination in starchy foods, the possibility of contamination in protein-rich foods, and the need to monitor food handling and hygiene. (Leong et al., Microb Pathog, 2023) [2]
Severe illness is rare but can be life-threatening. In a case series of five immunocompetent adults who ate fried rice balls heavily contaminated with B. cereus, symptoms ranged from vomiting and diarrhea to life-threatening acute liver failure and acute tubular necrosis of the kidney in the index patient. The leftover rice ball contained cereulide at 37 μg/g, one of the highest levels reported from foodborne outbreaks, and the toxin is notably resistant to heat and acid during cooking. (Schreiber et al., Toxins (Basel), 2022) [3]
Infection beyond the gut is uncommon and mostly affects vulnerable people. In a cluster of B. cereus bloodstream infections in neonatal care units, four preterm infants developed late-onset bacteremia between August and November 2019. All four survived after vancomycin-containing treatment, but one developed diffuse cerebritis and a brain abscess with severe neurologic sequelae. The authors describe B. cereus as rarely an opportunistic pathogen in invasive infections among immunocompromised patients. (Tsai et al., J Microbiol Immunol Infect, 2022) [4]
What Is Bacillus Cereus?
Bacillus cereus is a type of bacteria that causes food poisoning. You can get it from rice, meats, sauces, dairy, and other foods. It causes vomiting or diarrhea that lasts for a day or two. [5]
It's also possible to get a Bacillus cereus (B. cereus) infection in other parts of your body. These include your eyes, lungs, skin, and central nervous system (brain and spinal cord). These infections are rare and more likely to happen if you have a weakened immune system. [1]
What Are the Symptoms of B. cereus Food Poisoning?
Symptoms of Bacillus cereus food poisoning include:
Symptom | Description |
Abdominal pain or cramping | Discomfort in the stomach area |
Nausea | Feeling queasy or sick to the stomach |
Vomiting | Throwing up stomach contents |
Watery diarrhea | Loose, watery bowel movements |
How Do You Get Bacillus Cereus Food Poisoning?
B. cereus is common in soil, dust, and water, and it can get into the food you eat. [1]
If food isn't heated or stored properly, the bacteria can grow and give off toxins. [5] For example, bacteria can grow when cooked rice sits outside the fridge for too long. [1] [6] [5] Importantly, reheating or frying food doesn't always kill the bacteria or get rid of the toxins. [1] [5] You get sick when you eat food contaminated with the toxins or bacteria. [1]
Many different types of foods can cause B. cereus food poisoning:
Food category | Examples |
Dairy | Cheese and other dairy products |
Seafood | Fish, sushi |
Meat | Beef, poultry, and other meats |
Sauces and soups | Sauces, soups, and stews |
Starchy foods | Rice, pasta, and potatoes |
Produce | Vegetables |
Can the infection spread beyond the gut?
Yes, although it is rare. B. cereus infections can occasionally spread to other parts of the body, damaging your organs. [1] This is more likely to happen if you have a weakened immune system. [1]
What Are the Complications?
Complications of B. cereus food poisoning are rare. However, severe vomiting or diarrhea can lead to dehydration, which can be life-threatening. [1] And rarely, the infection can spread to other parts of your body, damaging your organs. [1]
How Is Bacillus Cereus Diagnosed?
Healthcare providers diagnose B. cereus by testing samples from the person who is sick and, when possible, from the food itself [5]:
Diagnostic test | What it looks for |
Stool sample | Bacteria or toxins in the digestive system |
Vomit sample | Bacteria or toxins from the stomach |
Blood sample | Signs of infection in the bloodstream |
Food sample | A certain amount of bacteria in the food you ate, to determine if that's what made you sick |
Providers look for a certain amount of bacteria in a sample of the food you ate to determine if that's what made you sick. [5]
How Is Bacillus Cereus Treated?
B. cereus food poisoning usually doesn't need treatment unless you have severe complications. [5] In many cases, the toxins in the food you ate, not the bacteria themselves, are making you sick. Antibiotics, which kill bacteria, wouldn't help in those cases. [1] [5]
Instead, your provider may suggest:
Care step | Purpose |
Plenty of rest | Lets your body recover |
Plenty of fluids | Helps you stay hydrated |
IV fluids | Recommended for severe diarrhea or vomiting |
What should I drink while recovering?
Drink water, broth, or electrolyte replacement drinks to prevent dehydration. [1]
When Should I Go to the Emergency Room?
Go to the emergency room if you have signs of a serious infection, especially if:
Warning sign | What it means |
Weakened immune system | Higher risk of serious infection |
Can't keep fluids down | Dehydration risk rises quickly |
Severe diarrhea | Fluid loss can become dangerous |
Weak, dizzy, or dehydrated | Signs your body is losing too much fluid |
What Can I Expect if I Have a B. cereus Infection?
B. cereus food poisoning usually goes away on its own. You should feel better within a few hours to two days. [1] [5] Drinking water, broth, or electrolyte replacement drinks during that time prevents dehydration. [1]
Can Bacillus Cereus Food Poisoning Be Prevented?
You can lower your risk of B. cereus food poisoning by cooking and storing your food safely:
Prevention step | Detail |
Refrigerate cooked leftovers quickly | Within two hours of cooking |
Keep cold food cold | At or below 38°F (4°C) |
Cook to safe temperatures | Reach the recommended safe internal temperature for each food |
When in doubt, throw it out | Discard any food that's been sitting out too long |
Properly cooking and storing food helps keep you safe from this common bacteria.
Conclusion
Bacillus cereus is a well-known cause of food poisoning [7], and it starts with a bacteria that lives quietly in soil, dust, and water before finding its way into rice, meats, sauces, dairy, fish, soups, sushi, and starchy staples. [1] The problem isn't the food itself but how it's handled: when food isn't heated or stored properly, the bacteria multiply and release toxins. [1] [5] Even reheating or frying doesn't reliably kill the bacteria or remove the toxins. [1] [5]
The good news is that most cases are short-lived and self-resolving: symptoms like abdominal cramping, nausea, vomiting, and watery diarrhea typically clear within a few hours to two days with rest and fluids. [1] [5] Antibiotics usually won't help, because the toxins, not the bacteria, do the damage. [1] [5] Complications like dehydration are rare, and infections beyond the gut are rarer still, mostly affecting people with weakened immune systems. [1] Your best defense is simple kitchen discipline: cook food to safe internal temperatures, refrigerate leftovers within two hours, keep cold food at or below 38°F, and throw out anything that's been sitting out too long. [1] And if you create health or food-safety education materials, Rinnit's infographic templates can help you turn kitchen-safety topics like this one into clear, visual guides for your audience.
Frequently Asked Questions
What is Bacillus cereus in simple terms?
Bacillus cereus is a type of bacteria that most often causes food poisoning. It causes vomiting or diarrhea that lasts for a day or two, and you can get it from rice, meats, sauces, dairy, and other foods. [1] [5]
Where does Bacillus cereus come from?
B. cereus is common in soil, dust, and water, and it can get into the food you eat. [1]
What foods carry Bacillus cereus?
Many foods can cause B. cereus food poisoning: cheese and other dairy products, fish, meat, sauces, soups and stews, starchy foods like rice, pasta, and potatoes, sushi, and vegetables. [1]
How does food make you sick?
If food isn't heated or stored properly, the bacteria can grow and give off toxins. [1] [5] For example, bacteria can grow when cooked rice sits outside the fridge for too long. [5] You get sick when you eat food contaminated with the toxins or bacteria. [5]
Does reheating or frying food kill the bacteria?
Not always. Reheating or frying food doesn't always kill the bacteria or get rid of the toxins. [1] [5]
What are the symptoms?
How long does Bacillus cereus food poisoning last?
Bacillus cereus food poisoning usually goes away on its own. You should feel better within a few hours to two days. [1] [5]
Does Bacillus cereus need antibiotics?
Usually not. In many cases, the toxins in the food you ate, not the bacteria themselves, are making you sick, so antibiotics (which kill bacteria) wouldn't help. [1] [5] Treatment is usually rest and plenty of fluids. [1] [5]
Can it cause serious complications?
Complications are rare, but severe vomiting or diarrhea can lead to dehydration, which can be life-threatening. Rarely, the infection can spread to other parts of your body, damaging your organs. [1]
Can Bacillus cereus infect other parts of the body?
Yes, though rarely. B. cereus infections can affect the eyes, lungs, skin, and central nervous system (brain and spinal cord), and are more likely to happen if you have a weakened immune system. [1]
How do providers diagnose it?
By testing a sample of your stool, vomit, or blood, and testing a sample of the food that made you sick. [1] Providers look for a certain amount of bacteria in the food sample to determine if that's what made you sick. [1] [5]
When should I go to the emergency room?
If you have signs of a serious infection, especially if you have a weakened immune system, can't keep fluids down, have severe diarrhea, or feel weak or dizzy or have other signs of dehydration. [1]
How do I prevent Bacillus cereus food poisoning?
Refrigerate cooked leftovers within two hours, keep cold food at or below 38°F (4°C), cook food to the recommended safe internal temperature, and throw out any food that's been sitting out too long. [1]
What should I drink while recovering?
Water, broth, or electrolyte replacement drinks to prevent dehydration. [1]
Related Reading
References
Cleveland Clinic. Bacillus cereus. Cleveland Clinic Health Library. Last updated January 23, 2026. Accessed October 15, 2026. https://my.clevelandclinic.org/health/diseases/23581-bacillus-cereus
Leong SS, Korel F, King JH. Bacillus cereus: a review of "fried rice syndrome" causative agents. Microb Pathog. 2023;185:106418. PMID: 37866551. https://doi.org/10.1016/j.micpath.2023.106418
Schreiber N, Hackl G, Reisinger AC, et al. Acute liver failure after ingestion of fried rice balls: a case series of Bacillus cereus food poisonings. Toxins (Basel). 2022;14(1):12. PMID: 35050989. https://doi.org/10.3390/toxins14010012
Tsai AL, Hsieh YC, Chen CJ, et al. Investigation of a cluster of Bacillus cereus bacteremia in neonatal care units. J Microbiol Immunol Infect. 2022;55(3):494-502. PMID: 34340907. https://doi.org/10.1016/j.jmii.2021.07.008
British Columbia Centre for Disease Control. Bacillus cereus. BCCDC Health Info. Accessed October 15, 2026. https://www.bccdc.ca/health-info/diseases-conditions/bacillus-cereus
Mayo Clinic Staff. Food poisoning (foodborne illness): symptoms and causes. Mayo Clinic. July 16, 2026. Accessed October 15, 2026. https://www.mayoclinic.org/diseases-conditions/food-poisoning/symptoms-causes/syc-20356230
Tewari A, Abdullah S. Bacillus cereus food poisoning: international and Indian perspective. J Food Sci Technol. 2015;52(5):2500-2511. PMID: 25892750. https://doi.org/10.1007/s13197-014-1344-4
Medical disclaimer
The information provided in this article is for educational purposes only and is not intended as medical advice. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. If you can't keep fluids down, have severe diarrhea, feel weak or dizzy, or have a weakened immune system and develop symptoms, seek medical care promptly.
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