Bacillus cereus is a gram-positive, spore-forming, motile aerobic rod that also grows well anaerobically. It is ubiquitous in the environment, frequently isolated from plants, meat, eggs, dried cereal, and dairy products.
PATHOGENESIS AND EPIDEMIOLOGY
B cereus commonly causes toxin-mediated foodborne illness due to the formation and release of an emetic and diarrheal toxins. Spores of this organism can survive pasteurizations, brief cooking, and boiling. The emetic form of disease is usually associated with the consumption of contaminated cooked rice (eg, fried rice). Unlike the diarrheal toxins, the emetic toxin is preformed in foods so the presence of living organism is not necessary to cause disease.
For infections not related to food consumption, neonates, immunocompromised hosts, intravenous drug users, patients with recent eye surgery or trauma, or those with intravascular devices or artificial prosthesis are at risk. B cereus does not persist in the intestine after ingestion and therefore is not spread by the fecal-oral route.
The 2 primary forms of infection due to B cereus are food poisoning and invasive disease. Further, there are 2 types of food poisoning due to B cereus. In both forms, the disease is due to the organism’s enterotoxin. If the food is contaminated with B cereus spores, the diarrheal form results, manifested as abdominal cramps and profuse, watery diarrhea, and in about 25% of patients, vomiting. Following ingestion of the preformed toxin, the emetic form results, manifested as nausea, vomiting, and abdominal cramps, followed by diarrhea in up to 30% of patients. Following the ingestion of the contaminated food, the incubation of the emetic form is less than 6 hours (similar to food poisoning due to Staphylococcus aureus) while the incubation period of the diarrhea form is more than 6 hours (similar to food poisoning due to Clostridium perfringens). Either form is usually mild and self-limited, lasting 6 to 24 hours, although the diarrhea form may be more severe than the emetic form. Fulminant liver failure has been associated with the emetic form.
B cereus is a significant cause of virulent posttraumatic endophthalmitis, typically following a penetrating injury or intravenous drug use. Severe pain, reduced visual acuity, chemosis, swelling, and proptosis, often with systemic symptoms, are noted. Full vision recovery is rare. Postsurgical, traumatic, or burn wounds due to B cereus and severe deep infections such as necrotizing fasciitis and gangrene have occurred.
B cereus bacteremia is reported among neonates, intravenous drug users, immunocompromised patients, and those with central lines. B cereus endocarditis is associated with intravenous drug use or valvular disease. Pneumonia is also reported in neonates and immunosuppressed patients. Meningitis and brain abscesses due to B cereus may occur in neonates or in children with ventricular shunts. A cluster of necrotizing enterocolitis was linked to B cereus contamination of human milk fortifier in ...