Bacillus Cereus


Article Author:
Rachel McDowell
Evan Sands


Article Editor:
Harvey Friedman


Editors In Chief:
Alexandra Caley
Sameh Boktor


Managing Editors:
Avais Raja
Orawan Chaigasame
Carrie Smith
Abdul Waheed
Khalid Alsayouri
Trevor Nezwek
Radia Jamil
Patrick Le
Anoosh Zafar Gondal
Saad Nazir
William Gossman
Hassam Zulfiqar
Hussain Sajjad
Steve Bhimji
Muhammad Hashmi
John Shell
Matthew Varacallo
Heba Mahdy
Ahmad Malik
Sarosh Vaqar
Mark Pellegrini
James Hughes
Beata Beatty
Beenish Sohail
Nazia Sadiq
Hajira Basit
Phillip Hynes


Updated:
7/5/2019 8:59:49 PM

Introduction

Bacillus cereus is a toxin-producing facultatively anaerobic gram-positive bacteria. The bacteria is commonly found in the environment, is often found in soil and vegetation, and can be present in foods.  It can quickly multiply at room temperature. There are two main types of an intestinal illness caused by B. cereus. One is diarrheal, and one leads more to nausea/vomiting. B. cereus has also been implicated in infections of the eye, respiratory tract, and in wounds. The pathogenicity of B. cereus, whether intestinal or nonintestinal, is intimately associated with the production of tissue-destructive exoenzymes. Among these secreted toxins are four hemolysins, three distinct phospholipases, an emesis-inducing toxin, and proteases.[1][2]

Etiology

B. cereus illness is related to many foods - beef, turkey, rice, beans, vegetables.  Specifically, the diarrheal illness is often related to meats, milk, vegetables, and fish.  The emetic-type illness is most often associated with rice products, but it has also been associated with other types of starchy products such as potato, pasta, and cheese products.  Some food-mixtures (sauces, puddings, soups, casseroles, pastries, and salads, have been associated with food-borne illness in general.[3][4]

Bacillus cereus is caused by ingestion of food contaminated with either the enterotoxigenic B. cereus, or with the emetic toxin.  In non-gastrointestinal illness, reports of respiratory infections similar to respiratory anthrax have been attributed to B. cereus strains harboring B. anthracistoxin genes. 

Epidemiology

The Centers for Disease Control (CDC) website states that there were 619 confirmed outbreaks of Bacillus-related poisoning from 1998 through 2015, involving 7385 illnesses. In this timeframe, there were 75 illnesses and three deaths due to confirmed Bacillus-related illness. The website states there were 19,119 outbreaks overall, and 373,531 illnesses.  It refers to 14,681 hospitalizations and 337 deaths. These statistics refer to all Bacillus-related illness, and not just B. cereus related illness.[5][6]

The Bad Bug Book further breaks this down and states there are an estimated 63,400 episodes of B. cereus illness annually in the United States. In 2005, 2006, and 2007 there were 13 confirmed outbreaks and 37.6 suspected outbreaks during this period, involving over 1000 people.

All people are considered to be susceptible to B. cereus infection. Mortality is rare. The emetic enterotoxin has been found to be associated with a few cases of liver failure and death in otherwise healthy people. There is a newly found cytotoxin which has been associated with a B. cereus strain that caused one confirmed outbreak and three deaths. The infective dose or the number of organisms most commonly associated with human illness is 10^5 to 10^8, but pathogenicity arises from the preformed toxin, not from the bacteria themselves.

Pathophysiology

There are two types of food-borne B. cereus illness. In the first, contaminated food (many types of food, often left at room temperature) makes its way to the small intestine where the toxin, in this case, a large-molecular-weight protein, is released. This can lead to diarrhea, cramps, and sometimes nausea. Usually, vomiting is not present in this form of illness. Incubation for the first type is 6 to 15 hours. In the second type, affected food, most often starchy food, and classically, rice, contains a different type of toxin (cereulide, an ionophoric low-molecular-weight dodecadepsipeptide that is pH-stable and heat and protease-resistant). This toxin causes emetic-type B. cereus illness.  The incubation period for this type is 30 minutes to 6 hours.

Endophthalmitis is a vision-threatening eye infection resulting from microbial infection of the inner eye. The hallmark of the ophthalmic lesion is a corneal ring abscess which may be accompanied by rapid progression of pain, proptosis, chemosis, retinal hemorrhage, and perivasculitis. Systemic manifestations include fever, leukocytosis, and general malaise.

Histopathology

The pathogenicity of B. cereus, whether inside or outside of the gastrointestinal (GI) tract, is associated with exoenzyme production. Among the secreted toxins are four hemolysins, three distinct phospholipases, an emesis-inducing toxin, and three pore-forming enterotoxins: hemolysin BL (HBL), nonhemolytic enterotoxin (NHE), and cytotoxin K. In the gastrointestinal tract (small intestine), vegetative cells, ingested as viable cells or spores, produce and secrete a protein enterotoxin and induce a diarrheal syndrome, whereas emetic toxin, a plasmid-encoded cyclic peptide (cereulide), is produced in food products and ingested as a formed toxin. In rabbit ligated ileal-loop assays, culture filtrates of enterotoxigenic strains induce fluid accumulation and hemolytic, cytotoxic, dermonecrotic, and vascular permeability activities in rabbit skin.

The enterotoxin is composed of a binding component (B) and two hemolytic components, designated HBL. Also diarrheagenic in the gastrointestinal tract is a nonhemolytic three-component enterotoxin, designated NHE. The emetic toxin, which induces a vomiting syndrome, is synthesized in the contaminated food product, usually rice, pasta or dairy products, in which B. cereus is growing and may represent a product of growth.

History and Physical

For diarrheal-type illness, symptoms include watery diarrhea and abdominal pain and cramping.  Some nausea can be associated, but rarely vomiting.  Symptom onset is usually within 6 to 15 hours of eating food that was left at room temperature (less than 140 degrees and more than 40 degrees) for more than 2 hours.

For emetic-type illness, symptoms include nausea and vomiting, similar to the presentation associated with Staphylococcus aureus food-borne illness. Symptom onset is generally within 30 minutes to 6 hours of consuming rice or starchy foods that were left at room temperature, even after they have been reheated.

Symptoms for both types usually resolve within 24 hours after onset. In complicated cases, severe manifestations can include severe systemic and pyogenic infections, septic meningitis, gangrene, cellulitis, panophthalmitis, lung abscess, infant death, and endocarditis. Risk factors for the complicated and severe disease include immunosuppression, intravenous drug abuse, and the neonatal period, as well as having an indwelling catheter or having a traumatic or surgical wound.

There is some difficulty differentiating B. cereus infections from other similar infections. The diarrheal type of B. cereus infection is very similar to Clostridium perfringens food poisoning. The symptoms of the emetic type parallel S. aureus.

Evaluation

B. cereus can be confirmed as the source of a foodborne outbreak by 1) isolation of strains of the same serotype from a food source and the feces or vomitus of a patient, 2) isolation of large numbers of B. cereus serotype known to cause foodborne illness from the food/feces/vomitus of a patient, or 3) isolation of B. cereus from suspect foods and confirmation of the enterotoxigenic through serology (for the diarrheal toxin) or biological tests (diarrheal and emetic).

In other infections like lung abscess and endophthalmitis, evaluation is made with whatever fluid is available. For example, the diagnosis of endophthalmitis can be made by the gram-staining of vitreous fluid.

Treatment / Management

Treatment is symptomatic. Most patients recover within 24 hours after symptom onset. However, in severe cases, IV fluid hydration is necessary.[7][8][9]

Regarding endophthalmitis, because of how quickly B. cereus destroys an infected eye, especially in cases of penetrating trauma with a foreign body, rapid therapeutic intervention is mandatory irrespective of results of immediate diagnostic testing. The outcome varies with the microbial agent involved and the rapidity of and response to treatment.

Enhancing Healthcare Team Outcomes

Bacillus cereus food poisoning is a relatively common presentation to the emergency department. Hence, nurses and nurse practitioners should be familiar with its presentation and management. The key feature about bacillus cereus poisoning is that the symptoms usually occur rapidly after ingestion of the contaminated food. However, the symptoms can be confused with C.difficile colitis. The diarrhea is watery and quite pronounced. Fortunately, the majority of patients only require oral hydration. Mortality is very rare with this infection.

 

 


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    Contributed by Frederick C. Michel, ASM
Attributed To: Contributed by Frederick C. Michel, ASM

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Bacillus Cereus - Questions

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A patient develops acute nausea, vomiting, and diarrhea 4 hours after eating at a Chinese restaurant. Which of the following is the most likely cause of his symptoms?



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What is the most common cause of food poisoning associated with reheated rice?



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An outbreak of watery diarrhea occurs in a group who ate the same fried rice the day before. What is the most likely causative agent?



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A metal worker presents to the emergency department with eye redness, fever, and generalized malaise. Exam reveals proptosis of the eye and severe chemosis. Due to the patient's decreased visual acuity, Ophthalmology was consulted and gram stain of the vitreous fluid reveals Gram-positive rods in high numbers. Which pathogen is the likely cause?



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What is the cause of the symptoms of Bacillus cereus foodborne illness?



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A previously healthy 34-year-old male presents to the emergency department complaining of abdominal cramping and diarrhea for 12 hours. His symptoms started a few hours after eating rice at a company picnic. He says multiple coworkers have the same symptoms. His vitals show a blood pressure of 132/82 mmHg, pulse 106/min, temperature 98.8 F, and respiratory rate 16/min. What is the next best step in the management of this patient?



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A 37-year-old man with a history of IV drug use and HIV presents with fever, left eye pain, and decreased visual acuity. On the physical exam, the patient’s left eye has a white milky substance at the base of the anterior chamber. Blood cultures later grow bacillus cereus. Which of the following will also likely be seen on physical exam?



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A previously healthy 48-year-old female presents to the emergency department with vomiting, diarrhea, and abdominal cramping for 2 days. She says that she ate reheated fried rice 6 hours prior to the onset of illness. On exam, she has scleral icterus and mild right upper quadrant tenderness on palpation. CBC is notable for a WBC count of 17600. AST is 850 IU/L, and ALT is 780 IU/L. Direct bilirubin is 1.2 mg/dL. Which toxin is most likely implicated in the patient’s illness?



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A 51-year-old male presents to the hospital with vomiting, abdominal cramping, and diarrhea after eating reheated rice. Which of the following elements from the patient’s past medical history increases his risk of developing a serious bacterial illness?



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Bacillus Cereus - References

References

Nguyen AT,Tallent SM, Screening food for Bacillus cereus toxins using whole genome sequencing. Food microbiology. 2019 Apr     [PubMed]
Hölzel CS,Tetens JL,Schwaiger K, Unraveling the Role of Vegetables in Spreading Antimicrobial-Resistant Bacteria: A Need for Quantitative Risk Assessment. Foodborne pathogens and disease. 2018 Nov     [PubMed]
Kimura 木村 啓太郎 K,Yokoyama 横山 智 S, Trends in the application of Bacillus in fermented foods. Current opinion in biotechnology. 2018 Sep 15     [PubMed]
Omer MK,Álvarez-Ordoñez A,Prieto M,Skjerve E,Asehun T,Alvseike OA, A Systematic Review of Bacterial Foodborne Outbreaks Related to Red Meat and Meat Products. Foodborne pathogens and disease. 2018 Oct     [PubMed]
May FJ,Polkinghorne BG,Fearnley EJ, Epidemiology of bacterial toxin-mediated foodborne gastroenteritis outbreaks in Australia, 2001 to 2013. Communicable diseases intelligence quarterly report. 2016 Dec 24     [PubMed]
Thein CC,Trinidad RM,Pavlin BI, A large foodborne outbreak on a small Pacific island. Pacific health dialog. 2010 Apr     [PubMed]
Meldrum RJ,Little CL,Sagoo S,Mithani V,McLauchlin J,de Pinna E, Assessment of the microbiological safety of salad vegetables and sauces from kebab take-away restaurants in the United Kingdom. Food microbiology. 2009 Sep     [PubMed]
Zhou G,Liu H,He J,Yuan Y,Yuan Z, The occurrence of Bacillus cereus, B. thuringiensis and B. mycoides in Chinese pasteurized full fat milk. International journal of food microbiology. 2008 Jan 31     [PubMed]
Warburton DW,Harrison B,Crawford C,Foster R,Fox C,Gour L,Purvis U, Current microbiological status of 'health foods' sold in Canada. International journal of food microbiology. 1998 Jun 30     [PubMed]

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