What is Bacillus Cereus?
Bacillus cereus is a type of bacteria that can produce harmful toxins. This bacterium is often found in our everyday environment and can easily contaminate food. If the conditions are right, like at room temperature, it can swiftly multiply and create large amounts of toxic substances. When these bacteria or their toxins are swallowed, they can cause various digestive system illnesses.
The problems caused by Bacillus cereus can range from diarrheal sickness without significant stomach issues to a condition which primarily affects the upper part of the digestive system, causing nausea and vomiting, but doesn’t result in diarrhea. Apart from the digestive system, Bacillus cereus is also known to infect eyes, the respiratory tract, and even wounds.
The harm done by Bacillus cereus, whether in the digestive system or elsewhere in the body, is closely linked to its ability to produce dangerous enzymes that can damage body tissues. These secreted toxins include substances known as hemolysins, phospholipases, and proteases, which break down certain components of our body’s cells.
What Causes Bacillus Cereus?
B. cereus is a common bacteria found everywhere in our environment. It’s special because it can form spores that help it survive in very hot or cold temperatures. This means it can easily contaminate a variety of foods, including beef, turkey, rice, beans, and vegetables.
The bacteria can cause two kinds of illnesses led by diarrhea and vomiting. Diarrhea is mainly linked with eating contaminated meat, milk, vegetables, or fish. Vomiting, on the other hand, is often tied to eating foods like rice and other starchy products, such as potatoes, pasta, and cheese.
It’s also been found in a range of mixed food dishes like sauces, puddings, soups, casseroles, pastries, and salads, which are commonly associated with food poisoning in general.
The illness caused by Bacillus cereus is caught by eating food that has been contaminated with it. In some rare cases, this bacteria can cause non-stomach related illnesses, for example, infections in the respiratory system that are similar to lung anthrax. This is usually because the strains of B. cereus have genes for the anthrax toxin.
Risk Factors and Frequency for Bacillus Cereus
Bacillus-related illnesses led to numerous outbreaks between 1998 and 2015, according to the CDC. In this period, there were 619 confirmed outbreaks resulting in 7385 illnesses, 75 of these resulted in serious illnesses, and there were three deaths. Overall, there were 19,119 outbreaks leading to 373,531 illnesses. Furthermore, there were 14,681 hospitalizations and 337 deaths due to all Bacillus-related illnesses, not just those related to B. cereus.
The FDA’s “Bad Bug Book” states that B. cereus is estimated to cause 63,400 illnesses each year within the U.S. From 2005 through 2007, there were 50 B. cereus outbreaks involving a total of over 1000 people.
All people are at risk of B. cereus infection. However, death from this infection is rare. A few cases have been reported where the emetic enterotoxin, a toxin produced by B. cereus, led to liver failure and death in otherwise healthy people. These toxins, not the bacteria themselves, are responsible for the illness. They usually arise when there are about 10^5 to 10^8 Bacillus organisms per gram in the body.
Signs and Symptoms of Bacillus Cereus
Bacillus cereus, a type of bacteria, can cause different types of disease, broadly categorized into gastrointestinal disease and infections outside the gastrointestinal system. The gastrointestinal diseases are either diarrheal type or emetic type, while the extra-gastrointestinal infections can affect various parts of the body.
The diarrheal illness caused by B. cereus involves symptoms like loose stools, abdominal pain, and cramping, usually without nausea and vomiting. These symptoms typically occur between 6 and 15 hours after eating food that’s been left out at room temperature, which gives the bacteria time to grow.
On the other hand, the emetic type of disease is generally characterized by nausea and vomiting. These symptoms resemble food poisoning caused by a bacteria called Staphylococcus aureus. The symptoms often appear between half an hour and 6 hours after eating rice or starchy food left at room temperature. There is often diarrhea as well. Symptoms for both types of gastrointestinal infections usually go away within a day.
Outside the digestive system, B. cereus can cause a variety of illnesses.
- One of the most common is an eye infection called endophthalmitis, marked by a lesion on the cornea and other symptoms like fever, a white blood cell increase, and generally feeling unwell. This type of infection is generally caused by an injury that breaks the skin of the eye.
- The bacteria can also infect the blood or the heart, a condition known as bacteremia or endocarditis. This usually happens among intravenous drug users, people with central venous access catheters, or people with damaged mucus membranes, as well as those with weakened immune systems.
- When B. cereus enters through wounds, it can give rise to skin and bone infections. This can occur from things like gunshot wounds, fractures, animal bites, and burns. It can cause skin infections (cellulitis) or severe skin and flesh infections (necrotizing soft tissue infections). It can also cause infection at sites of chronic bone infections (osteomyelitis).
- Lastly, people can get keratitis, a corneal infection, from B. cereus invading the cornea, especially after an abrasion. This can occur after wearing contact lenses.
Testing for Bacillus Cereus
If there’s an outbreak of food-borne illness caused by B. cereus, it can be confirmed by doing one of three things: first, the bacteria can be isolated from the same type of food that a patient ate, and from the patient’s stool or vomit. Second, a large number of B. cereus bacteria, known to cause foodborne illnesses, can be isolated from food and/or a patient’s vomit or stool. Lastly, B. cereus could be found in the suspect food, and tests can show the presence of certain toxins.
In infections occurring outside the intestines, the disease can be examined by analyzing body fluids. For instance, endophthalmitis, an eye infection, can be diagnosed by performing a gram-stain test on the fluid from the eye.
It’s important to note that when the bacillus species is found in blood tests, it’s commonly seen as contamination. However, in certain medical situations, it should be treated as true bacteria in the blood, not contamination.
Treatment Options for Bacillus Cereus
Generally, infections caused by B. cereus—commonly known as Bacillus cereus—are typically limited and do not call for special treatment. Most patients need only oral hydration and symptom management and usually feel better within a day of symptom start. Prescribing antibiotics in these cases is unnecessary. For severe cases, patients may need to receive hydration through an IV, or intravenous method.
When B. cereus affects the eye, serious damage can quickly occur, particularly when the eye experiences trauma like a penetrating injury caused by a foreign object. In these cases, immediate treatment is critical, even before we receive diagnostic test results. The success of the treatment often depends on the speed of response and the particular bacteria causing the infection.
B. cereus is known to produce substances called beta-lactamases, which makes it resistant to a group of antibiotics known as beta-lactam antibiotics. If treatment needs to involve antibiotics, healthcare providers might consider vancomycin, gentamicin, chloramphenicol, or carbapenems. Clindamycin, tetracycline, and erythromycin have shown mixed results and are not typically the first choice.
A 2007 study showed that B. cereus species, in general, resisted two types of antibiotics: trimethoprim/sulfamethoxazole and beta-lactam antibiotics. Some species also resisted clindamycin and erythromycin. In that same study, however, all B. cereus samples could still be treated with a wide range of other antibiotics such as chloramphenicol, ciprofloxacin, gentamicin, vancomycin, among others.
In extreme cases, where there is a risk of the infection spreading to the entire body, treatment might need to be administered in multiple ways at the same time. For instance, a patient might receive medication both intravenously and directly inside the eye.
What else can Bacillus Cereus be?
There are various conditions that may trigger similar symptoms which often leads to a complex diagnosis. These include:
- Various viral infections like Rotavirus
- Bacterial infections such as Campylobacter, Shigella, Salmonella, Escherichia coli, Yersinia enterocolitica, Vibrio cholerae, and Clostridium difficile
- Parasitic infections caused by organisms like Giardia, Cryptosporidium, Entameba, Microsporidium, and Cyclospora
- Effects of toxins, such as those produced by Staphylococcus aureus
- Appendicitis, which is inflammation of the appendix
- Diverticulitis, this condition causes inflammation or infection in small pouches in the colon
- Mesenteric ischemia, which is decreased blood flow to your intestines.
It’s important for doctors to carefully identify these conditions and conduct the required tests to make an accurate diagnosis.
What to expect with Bacillus Cereus
Patients undergoing steroid therapy, those in hospital, and those with a low white blood cell count (neutropenia) might struggle with a more severe outcome when infected with B. cereus bacteremia, a type of blood infection. This is notably worse in patients who also have blood cancers.
One finding reported that these patients often experienced neurological symptoms, not just stomach-related issues. This research also found a link between these infections and the use of central venous catheters, utilized for medical treatments such as chemotherapy. Tragically, of the 12 patients in this study, 4 passed away due to B. cereus septicemia, which can be attributed to delays in appropriate antibiotic treatment, liver problems, and involvement of the brain and nervous system.
Unfortunately, even when prescribed antibiotics promptly, newborns infected with B. cereus generally had a poor outcome.
Possible Complications When Diagnosed with Bacillus Cereus
While complications of digestive issues related to B. cereus infections are rare, they mainly affect individuals with weakened immune systems. These complications can extend beyond the intestinal system, causing conditions like:
- Gangrene
- Cellulitis
- Aseptic meningitis
- Bloodstream infection (septicemia)
- Death
Preventing Bacillus Cereus
It’s crucial to teach patients about the importance of washing their hands regularly. This simple act can help prevent the spread of bacterial infections. In addition, patients should have accessible written information on the correct methods for receiving, handling, preparing and storing food. This knowledge can significantly help prevent food-related infections.
