What is Bacillus cereus (B. cereus)?

From the Guidelines

Bacillus cereus is a significant cause of foodborne illness, particularly in long-term care facilities, and its diagnosis is primarily based on the abrupt onset of nausea, vomiting, abdominal cramps, and diarrhea within 1–72 h after ingestion of suspect foods in multiple patients 1.

Key Characteristics of Bacillus cereus Infections

• Bacillus cereus can cause two types of foodborne illness: an emetic (vomiting) syndrome and a diarrheal syndrome, with the emetic syndrome typically occurring 1-5 hours after consuming contaminated food, and the diarrheal syndrome appearing 8-16 hours after consumption.
• The bacterium forms spores that can survive cooking temperatures and germinate when food cools, making proper food handling crucial for prevention.
• Treatment is generally supportive with fluid replacement, as symptoms typically resolve within 24 hours, and antibiotics are rarely needed except in severe systemic infections, which are uncommon.

Prevention and Control Measures

• Stringent infection control procedures are mandated to prevent the transmission of Bacillus cereus, including vigorous hand-washing with soap, friction, and running water, as alcohol hand preparations may not completely inactivate the organism 1.
• Proper food handling and storage are essential to prevent the growth of Bacillus cereus, particularly in starchy foods like rice that have been cooked and left at room temperature.

Diagnosis and Detection

• The diagnosis of Bacillus cereus infection is made solely on the basis of the abrupt onset of nausea, vomiting, abdominal cramps, and diarrhea within 1–72 h after ingestion of suspect foods in multiple patients.
• Antigen detection may be more sensitive than examination of stool specimens for trophozoites and for cysts in diagnosing infections with other organisms, but the diagnosis of Bacillus cereus is primarily clinical 1.

From the Research

Bacillus cereus Characteristics

• Bacillus cereus is a pathogen that can cause nosocomial bloodstream infections (BSIs) 2
• It is mostly caused by venous catheter-related infections 2
• The main sources of B. cereus infections are hospital environments, such as ventilator equipment, intravascular catheters, and linen 3

Antimicrobial Susceptibility

• B. cereus isolates are generally susceptible to vancomycin, gentamicin, and imipenem 2
• However, some isolates may be resistant to clindamycin (65.5%) and levofloxacin (10.3%) 2
• Vancomycin and ciprofloxacin have been shown to be effective against B. cereus isolates in vitro 4
• The minimum inhibition concentration (MIC) of vancomycin and ciprofloxacin against B. cereus isolates can vary 4

Treatment and Outcomes

• Appropriate empirical therapy is important to achieve early clinical resolution in B. cereus BSI 2
• Vancomycin is one of the appropriate selections of empirical therapy for B. cereus BSI 2
• Early intravitreal injection of vancomycin or gatifloxacin can improve the therapeutic outcome of B. cereus endophthalmitis 5
• Delay in treatment past 6 hours can significantly reduce the potential for salvaging useful vision in B. cereus endophthalmitis 5

Epidemiology and Prevention

• B. cereus is a serious cause of nosocomial infections, with a high potential for hospital-cross-contaminations and inter-hospital contaminations 6
• Identical B. cereus strains can be recovered from different patients and hospital environments for up to 2 years 6
• Effective preventive measures include sterilization of devices, educating medical staff on disinfection methods, and ensuring proper catheter placement and care 3