Bacillus cereus – Habitat, Morphology, Pathogenicity, Virulence Factors

Domain:	Bacteria
Phylum:	“Firmicutes”
Class:	Bacilli
Order:	Bacillales
Family:	Bacillaceae
Genus:	Bacillus
Species:	B. cereus

• Bacillus cereus is a gram-positive, rod-shaped bacterium known for its toxin-producing capabilities and facultative anaerobic nature. This bacterium is prevalent in diverse environments, including soil and food products, due to its ability to form resilient spores. These spores enable B. cereus to survive extreme conditions and persist in various foodstuffs, including meats, vegetables, and grains.
• When ingested, Bacillus cereus can lead to two distinct types of gastrointestinal illness: emetic and diarrheal syndromes. The emetic syndrome is primarily associated with rice and starchy foods contaminated with cereulide, a potent toxin that induces vomiting. Conversely, the diarrheal syndrome is linked to the consumption of foods contaminated with enterotoxins that cause diarrhea. Each syndrome reflects the type of toxin present and the site of its action—either the stomach or the intestines.
• The pathogenic mechanisms of Bacillus cereus involve the production of various tissue-destructive exoenzymes. Key among these are hemolysins, phospholipases, and proteases, which contribute to its virulence by damaging host tissues and facilitating infection. Some B. cereus strains are also noted for causing infections beyond the gastrointestinal tract, such as in the eyes, respiratory tract, and wounds, particularly when strains possess genes similar to those of Bacillus anthracis.
• Bacillus cereus is not only a pathogen but also demonstrates a broad ecological role. Some strains are used beneficially as probiotics or exhibit mutualistic relationships with plants. The bacterium’s ability to form endospores allows it to endure harsh environmental conditions, contributing to its prevalence in various settings.
• The taxonomic classification of Bacillus cereus places it within a group that includes several closely related species, such as Bacillus thuringiensis and Bacillus anthracis. Recent phylogenomic analyses have shown significant genetic overlap among these species, highlighting their evolutionary connections.
• Historically, Bacillus cereus was first isolated in 1887 from a gelatine plate. Today, it is a well-recognized contaminant in the food industry, as evidenced by frequent warnings from regulatory agencies like the US Food and Drug Administration.
• Emerging research continues to reveal novel enzymes produced by Bacillus cereus, such as AlkC and AlkD, which are involved in DNA repair. These findings expand our understanding of the bacterium’s biochemical capabilities and potential applications in biotechnology.
• Overall, Bacillus cereus serves as a significant example of how environmental microorganisms can impact human health through foodborne illnesses and highlights the ongoing need for research to manage its presence in various contexts.

Definition of Bacillus cereus

Bacillus cereus is a gram-positive, rod-shaped bacterium that produces toxins leading to foodborne illnesses. It can cause two main types of gastrointestinal disorders: emetic (vomiting) syndrome and diarrheal syndrome. This bacterium is commonly found in soil and food, where it can survive as spores in harsh conditions.

What is the habitat of Bacillus cereus?

Bacillus cereus is a versatile bacterium with a wide range of habitats, which include:

• Soil and Environment: This bacterium is commonly found in soil, where it forms spores that can persist in various conditions. These spores contribute to its widespread distribution in the environment.
• Food Products: Bacillus cereus is frequently isolated from a variety of food sources such as vegetables, cereals, milk, spices, fried rice, cooked poultry, meats, soups, and desserts. Specific examples include mashed potatoes, beef stew, and hot chocolates sold in vending machines.
• Improper Food Handling Areas: It can also be found in areas with poor food handling practices, which may lead to contamination and subsequent foodborne illness.
• Microbial Communities: In the rhizosphere, the region surrounding plant roots, Bacillus cereus interacts with other microorganisms, contributing to the complex microbial ecosystem. It is also present in the gut microflora of invertebrates, including arthropods such as sowbugs, roaches, and termites, where it acts as an intestinal symbiont.
• Resilience to Environmental Factors: The endospores of Bacillus cereus exhibit significant resistance to physical and chemical agents, including heat, cold, desiccation, radiation, disinfection, and antibiotics. This resilience allows it to survive in harsh conditions and environments.
• Colonization: While not a normal human flora, Bacillus cereus may transiently colonize human skin, gastrointestinal tract, or respiratory tract. It can also colonize distilled liquors and alcohol-soaked swabs and pads, often evading typical disinfection methods.

What is the epidemiology of Bacillus cereus?

Bacillus cereus is a notable pathogen due to its ability to cause foodborne illness. Understanding the epidemiology of B. cereus involves examining its frequency of infection, the impact on public health, and the conditions under which outbreaks occur.

• Incidence and Outbreaks
  • Historical Data: According to data from the Centers for Disease Control and Prevention (CDC), there were 619 confirmed outbreaks of Bacillus-related poisoning between 1998 and 2015. This period saw 7,385 cases of illness and 75 documented illnesses attributed to B. cereus. Among these, three deaths were reported.
  • Current Estimates: The FDA “Bad Bug Book” estimates approximately 63,400 cases of B. cereus illness annually in the United States. Between 2005 and 2007, 13 confirmed outbreaks and 37.6 suspected outbreaks involved over 1,000 individuals.
• Pathogenicity and Susceptibility
  • Infective Dose: The pathogenic mechanism of B. cereus is largely attributed to the preformed toxins rather than the bacteria itself. The infective dose typically ranges from 10^5 to 10^8 organisms per gram of contaminated food. This high dose underscores the importance of proper food handling and hygiene to prevent contamination.
  • Toxin-Related Illnesses: The emetic enterotoxin produced by B. cereus is associated with severe cases, including liver failure and, although rare, death in otherwise healthy individuals. The severity of illness is linked to the amount and type of toxin ingested, highlighting the role of toxins in disease outcomes.
• Impact on Public Health
  • Hospitalization and Mortality: Out of the total Bacillus-related outbreaks and illnesses reported by the CDC, there were 14,681 hospitalizations and 337 deaths. These figures encompass all Bacillus species, not solely B. cereus. Mortality from B. cereus infections is infrequent but can be serious in certain cases.
• Transmission and Control
  • Susceptibility: While B. cereus can infect anyone, the risk of severe illness is relatively low. Proper food safety practices, such as maintaining appropriate cooking and storage temperatures, are crucial in minimizing the risk of B. cereus contamination.
  • Preventive Measures: Effective control measures include thorough cooking of food, maintaining good hygiene, and proper food storage to inhibit bacterial growth and toxin formation.

What is the morphology of Bacillus cereus?

• Cell Shape and Arrangement: Bacillus cereus is characterized by its gram-positive, rod-shaped morphology. The cells typically have square ends and can appear singly or in short chains. These rods are straight or slightly curved, with clear junctions visible between the cells in chains.
• Gram Staining Characteristics: Although Bacillus cereus is generally gram-positive, it may occasionally exhibit gram-variable or even gram-negative staining with age or under certain conditions. This variability does not significantly impact its identification.
• Spore Formation: The bacterium is non-capsulated but forms endospores that are central and ellipsoidal (oval-shaped). These spores do not cause the mother cell to swell and are not typically found in animal blood, tissues, or aerobic cultures. This spore formation is crucial for its survival under adverse conditions.
• Size and Structure: Bacillus cereus cells are approximately 1×3-4 µm in size. The size and shape contribute to its distinctive appearance under the microscope.
• Motility: The bacterium is motile, exhibiting two types of motility: swimming and swarming. It is equipped with peritrichous flagella, which are distributed around the cell and enable its movement.
• Environmental Resilience: The endospores of Bacillus cereus are highly resilient, capable of surviving extended periods of exposure to air and other harsh environmental conditions. This resilience is a key factor in its ability to persist in various habitats.
• Hemolytic Activity: Bacillus cereus is a beta-hemolytic bacterium, meaning it can lyse red blood cells and cause a clearing around colonies on blood agar plates. This hemolytic activity is associated with its pathogenic properties.
• Virulence Factors: The bacterium produces several virulence factors, including cerolysin and phospholipase, which contribute to its ability to cause disease by damaging host tissues and disrupting cellular functions.

What is the genome structure of Bacillus cereus?

• Overall Genome Size: The genome of Bacillus cereus comprises over 5 million base pairs (bp) of DNA. This extensive genome includes approximately 5481 genes, with around 5234 encoding proteins.
• Key Gene Categories: The genome is rich in genes related to various functions:
  • Metabolic Processes: Genes involved in metabolic pathways that enable the bacterium to utilize different nutrients.
  • Protein Processing: Genes responsible for synthesizing and modifying proteins.
  • Virulence Factors: Genes encoding factors that contribute to the bacterium’s pathogenicity.
  • Stress Response: Genes that help the bacterium respond to environmental stresses.
  • Defense Mechanisms: Genes that aid in protecting the bacterium from threats such as antibiotics.
• Virulence and Stress Response: Many genes associated with virulence, stress responses, and defense mechanisms also play roles in antibiotic resistance. This highlights the bacterium’s ability to survive and thrive in various conditions, including hostile environments.
• Core and Pan-Genome: About 600 genes are conserved across 99% of the Bacillus cereus sensu lato group, constituting roughly 1% of the total pan-genome. The pan-genome, which includes all genes present in any strain, is continually expanding due to frequent horizontal gene transfer.
• GC Content: The guanine-cytosine (GC) content of the DNA across all Bacillus cereus strains is approximately 35%. This percentage reflects the overall nucleotide composition and can influence the stability of the genome.
• Acid Shock Response: The arginine deiminase gene, arcA, is notably up-regulated in response to non-lethal acid shock at pH 5.4-5.5. This gene, part of the arcABC operon, is crucial for the bacterium’s survival in acidic environments, similar to its role in other bacteria like Listeria monocytogenes.
• Quorum-Sensing and Virulence Regulation: Virulence factors in Bacillus cereus are regulated through quorum-sensing mechanisms. The Phospholipase C regulator (PlcR) controls the expression of these factors, with its activity peaking during the stationary phase of growth. The small peptide PapR enhances PlcR’s function by activating transcription of virulence genes. Disruption of plcR using CRISPR/Cas9 results in loss of hemolytic and phospholipase activities, underscoring its critical role in virulence.
• Flagellar Genes: The bacterium’s motility is governed by 2 to 5 fla genes, varying with different strains. These genes encode the components of flagella necessary for movement.
• Chromosomal Structure: The circular chromosome of Bacillus cereus spans 5,411,809 nucleotides. It includes 147 structural RNA genes and 5366 RNA operons, contributing to its complex regulatory and functional networks.
• Plasmids: Bacillus cereus possesses plasmids ranging in size from 5 to 500 kilobases (kb). These plasmids can carry additional genes that may influence various physiological processes and contribute to the bacterium’s adaptability.

What are the cultural characteristics of Bacillus cereus?

• General Growth Conditions:
  • Bacillus cereus thrives on a variety of media, including nutrient agar and peptone media.
  • The bacterium is mesophilic, with optimal growth occurring between 20°C and 40°C, typically at around 37°C.
  • B. cereus demonstrates adaptability to a wide range of environmental conditions, reflecting its versatile nature.
• Colony Appearance on Nutrient Agar:
  • At 37°C, colonies of B. cereus on nutrient agar are large, ranging from 2 to 5 mm in diameter.
  • The colonies are grey-white and exhibit a granular texture. The edges of these colonies are less wavy, and the consistency is less membranous compared to other bacterial colonies.
• Colony Characteristics on 5% Sheep Blood Agar:
  • On 5% sheep blood agar at 37°C, B. cereus colonies are large, feathery, and dull gray.
  • These colonies have a granular and spreading appearance with a rough, matted surface and irregular perimeters.
  • B. cereus is beta-hemolytic on blood agar, meaning it can lyse red blood cells and create a clear zone around the colonies.
  • The irregular colony perimeters suggest swarming motility, where the bacterium spreads outward from the initial inoculation site.
• Development of Smooth Colonies:
  • In some cases, B. cereus colonies can appear smooth, either alone or mixed with rough colonies.
  • Smooth colonies, when grown away from the initial inoculum, are often surrounded by a uniform zone of beta-hemolysis, which frames the central colony.
• MYP Agar:
  • MYP (mannitol-egg yolk-polymyxin) agar has traditionally been used for isolating B. cereus. However, it has limited selectivity and may allow background flora to mask the presence of B. cereus.
  • Colonies on MYP agar are typically lecithinase-positive and mannitol-negative.
• Chromogenic Agar:
  • Bacara agar is a chromogenic selective and differential medium specifically designed to promote the growth and identification of B. cereus while inhibiting background flora.
  • On Bacara agar, B. cereus colonies appear pink-orange with an opaque halo, which aids in distinguishing them from other microorganisms.
  • This medium is suggested as a superior alternative to MYP agar for the enumeration of the B. cereus group, with colonies displaying a uniform pink-orange color surrounded by a zone of precipitation.

Media	Growth Temperature	Colony Characteristics	Notes
Nutrient Agar	37°C	– Large colonies (2-5 mm) – Grey-white – Granular texture – Less wavy edges and membranous consistency	– General growth medium – Shows typical colony morphology
5% Sheep Blood Agar	37°C	– Large, feathery colonies – Dull gray – Granular and spreading – Rough, matted surface – Irregular perimeters	– Beta-hemolytic (lyses red blood cells) – Shows swarming motility
MYP Agar	37°C	– Lecithinase-positive – Mannitol-negative	– Limited selectivity – Background flora can mask colonies
Bacara Agar	37°C	– Pink-orange colonies – Opaque halo – Uniform color with zone of precipitation	– Chromogenic, selective, and differential – Inhibits background flora

What is the ecology of Bacillus cereus?

Like many Bacilli of the world, the main environment for Bacillus cereus is the land. Together with Arbuscular mycorrhiza (and Rhizobium leguminosarum in clover) they are able to regenerate soils made of heavy metals by increasing the phosphorus, nitrogen and potassium levels in specific plants.

B. cereus can compete with other microorganisms like Salmonella as well as Campylobacter within the gut. its presence can reduce the number of microorganisms. In animals that eat food, such as rabbits, chickens and pigs, certain harmless species from B. cereus have been utilized as a probiotic additive to feed to help reduce Salmonella in the animal’s digestive tract and cecum. This helps improve the animal’s development, and the food safety for humans who consume these animals. B. cereus is a parasite that can infect Codling moth larvae.

B. cereus as well as the other members of Bacillus aren’t readily killed by alcohol, but they are recognized to infect distilled liquors and alcohol-soaked swabs as well as pads in sufficient numbers to cause an infection. Certain varieties from B. cereus can produce cereins, bacteriocins that are active against various B. cereus species, or different Gram-positive bacteria.

What are the characteristics of Bacillus cereus?

Test type	Test	Characteristics
Colony characters	Size	Medium
	Type	Round
	Color	Whitish
	Shape	Convex
Morphological characters	Shape	Rod
Physiological characters	Motility	+
	Growth at 6.5% NaCl	+
Biochemical characters	Gram’s staining	+
	Oxidase	+
	Catalase	+
	Oxidative-Fermentative	Fermentative
	Motility	+
	Methyl Red	–
	Voges-Proskauer	+
	Indole	–
	H2S Production	–
	Urease	V
	Nitrate reductase	+
	β-Galactosidase	–
Hydrolysis of	Gelatin	+
	Aesculin	+
	Casein	+
	Tween 40	+
	Tween 60	+
	Tween 80	+
Acid production from	Glycerol	+
	Galactose	V
	D-Glucose	+
	D-Fructose	+
	D-Mannose	–
	Mannitol	+
	N-Acetylglucosamine	+
	Amygdalin	+
	Maltose	+
	D-Melibiose	+
	D-Trehalose	+
	Glycogen	+
	D-Turanose	V

What is the pathogenicity of Bacillus cereus?

• Bacillus cereus is commonly linked to food poisoning and can cause various infections, including post-traumatic ophthalmitis. This ocular infection requires prompt and aggressive treatment to prevent severe outcomes.
• The bacterium is prevalent in environmental sources and raw foods, particularly in cereals like rice.
• Infections can manifest in different ways depending on the type of toxin involved.

What are the virulence factors of Bacillus cereus?

1. Enterotoxins
   • Bacillus cereus produces two primary enterotoxins that contribute to foodborne illnesses:
     • Heat-Stable Enterotoxin
       • Function: Causes the emetic (vomiting) form of food poisoning.
       • Mechanism: The precise mechanism remains unclear. It is resistant to heat and proteolysis.
       • Symptoms: Nausea, vomiting, abdominal cramps, and occasionally diarrhea. Symptoms typically resolve within 24 hours.
     • Heat-Labile Enterotoxin
       • Function: Responsible for the diarrheal form of the disease.
       • Mechanism: Stimulates the adenylate cyclase–cyclic adenosine monophosphate (cAMP) system in intestinal epithelial cells, leading to profuse watery diarrhea.
       • Symptoms: Profuse diarrhea, abdominal pain, and cramps. Fever and vomiting are rare. Incubation period ranges from 1 to 24 hours.
2. Other Toxins
   • Necrotic Toxin
     • Type: Heat-labile enterotoxin.
     • Function: Contributes to tissue damage and necrosis, particularly in ocular infections.
   • Cereolysin
     • Function: A potent cytotoxin that disrupts cellular membranes.
   • Phospholipase C
     • Function: Acts as a lecithinase, degrading phospholipids in cell membranes and contributing to tissue destruction.

What is the infection and disease context of Bacillus cereus?

• Bacillus cereus is frequently involved in opportunistic infections, particularly in individuals with compromised immune systems.
  • Opportunistic Infections
    • Common in post-traumatic eye infections, endocarditis, and bacteremia.
    • Pathogenesis of ocular infections is often complex and involves multiple toxins.
  • Infections in Immunocompromised Individuals
    • May lead to persistent bacteremia and sepsis, especially in the presence of foreign intravascular devices.
    • Skin colonization can occur transiently and may be recovered as minor contaminants in blood cultures.
    • Severe infections are typically seen in intravenous drug users or immunocompromised patients.

What are the clinical manifestations of Bacillus cereus infections?

1. Food Poisoning

Bacillus cereus is known for causing two distinct forms of food poisoning, each with specific clinical manifestations:

• Emetic Form (Vomiting Disease)
  • Cause: This form results from the consumption of rice contaminated with Bacillus cereus spores. The spores survive cooking and can germinate if the rice is not properly stored.
  • Mechanism: The heat-stable enterotoxin produced by the bacteria causes the symptoms. This toxin remains active even if the rice is reheated.
  • Incubation Period: Symptoms typically appear within 1 to 6 hours after ingestion.
  • Duration: The illness is usually brief, lasting less than 24 hours.
  • Symptoms: Characterized by vomiting, nausea, and abdominal cramps. Fever and diarrhea are generally not present.
• Diarrheal Form
  • Cause: This form is associated with the ingestion of contaminated meat, vegetables, or sauces. The bacteria proliferate in the intestines.
  • Mechanism: The heat-labile enterotoxin is released after the bacteria multiply in the intestinal tract. This toxin stimulates the secretion of fluids and electrolytes, leading to diarrhea.
  • Incubation Period: Symptoms appear after a longer incubation period, ranging from 1 to 24 hours.
  • Duration: The illness may last for several days.
  • Symptoms: Includes profuse watery diarrhea, nausea, and abdominal cramps. Fever and vomiting are uncommon.

2. Ocular Infections

• Cause: These infections typically occur following traumatic injuries to the eye, often involving soil or other contaminated materials.
• Types of Infections:
  • Keratitis: Inflammation of the cornea.
  • Endophthalmitis: Severe infection within the eye, affecting internal structures.
• Symptoms: Includes severe pain, redness, vision loss, and possible purulent discharge. Immediate medical intervention is necessary to prevent vision loss.

3. Other Infections

• Bacillus cereus can also cause a range of other infections, particularly in individuals with predisposing conditions:
  • Localized Infections
    • Wound Infections: Often associated with traumatic injuries or surgical wounds.
  • Systemic Infections
    • Endocarditis: Infection of the heart valves.
    • Catheter-Associated Bacteremia: Infection linked to intravenous catheters.
    • Central Nervous System Infections: Including meningitis or brain abscesses.
    • Osteomyelitis: Infection of the bone.
    • Pneumonia: Lung infection.
• Predisposing Factors: Presence of medical devices, intravenous drug use, and immunocompromised states increase susceptibility to these infections.

How is Bacillus cereus diagnosed in the laboratory?

Accurate laboratory diagnosis of Bacillus cereus involves a combination of direct detection methods, culture techniques, biochemical analysis, serodiagnosis, and molecular methods. Each of these approaches plays a crucial role in identifying the presence of this pathogen and determining its characteristics.

1. Specimens for Analysis

• Feces: Commonly collected for diagnosing gastrointestinal infections.
• Vomitus: Relevant in cases of food poisoning.
• Remaining Food: If available, useful for identifying contamination sources.
• Eye Specimen (Corneal Swab): Collected in cases of ocular infections.

2. Direct Detection Methods

• Microscopy
  • Gram Staining: Bacillus cereus appears as large, gram-positive rods arranged singly, in pairs, or in a serpentine pattern with square ends.
  • Endospore Formation: Endospores are visible as unstained, oval or round regions within the center of the cell. The spores are ellipsoidal and do not cause swelling of the mother cell.
• Gram Stain Image: A Gram stain image would typically show the characteristic large, gram-positive rods of Bacillus cereus.

3. Culture Techniques

• Media Used
  • 5% Sheep Blood Agar: Colonies appear large, feathery, dull gray, granular, opaque with a rough surface and irregular edges. Colonies are beta-hemolytic.
  • Chocolate Agar, Routine Blood Culture Media, and Nutrient Broths: Support growth under standard conditions.
• Incubation Conditions
  • Temperature: 35°C is optimal for growth.
  • Atmosphere: Ambient air or 5% carbon dioxide (CO₂).
• Selective Media for Isolation
  • MYPA (Mannitol, Egg Yolk, Polymyxin, Phenol Red Agar): Selective for Bacillus cereus due to its phospholipase C positive reaction and lack of mannitol fermentation.
  • PEMBA (Polymyxin, Egg Yolk, Mannitol, Bromothymol Blue Agar): Uses polymyxin and egg yolk to inhibit other flora and enhance detection.

4. Biochemical Analysis

• Catalase: Positive, indicating the ability to break down hydrogen peroxide.
• Oxidase: Negative, lacking cytochrome c oxidase enzyme.
• Oxidative Fermentation (OF) Test: Fermentative.
• Indole: Negative, no production of indole from tryptophan.
• Methyl Red: Positive, indicating mixed acid fermentation.
• Voges-Proskauer: Positive, indicating acetoin production.
• Glucose: Fermentative with acid production.
• Sucrose: Fermentative with acid production.
• Lactose: No fermentation.
• Starch Hydrolysis: Positive, indicating the ability to break down starch.
• Nitrate Reduction: Positive, showing the reduction of nitrate to nitrite.
• Gelatin Hydrolysis: Positive, indicating the breakdown of gelatin.
• Spore Staining: Endospore-forming bacteria.
• Motility: Motile, indicating the ability to move.

5. Serodiagnosis

• Detection Methods
  • Microslide Gel Diffusion Test: Used to detect Bacillus cereus toxins in food and feces. This method identifies the presence of specific toxins produced by the bacteria.

6. Molecular Methods

• Multiplex PCR: Analyzes the toxigenic potential of Bacillus cereus isolates by detecting genes encoding emetic-toxin cereulide (ces) and enterotoxins (nhe, hbl, and cytK). This method provides detailed information about the genetic basis for toxin production and pathogenicity.

What is the treatment for Bacillus cereus infections?

1. Food Poisoning

• Supportive Treatment:
  • Hydration: The primary approach for managing Bacillus cereus food poisoning is supportive care. This includes oral rehydration solutions to replace lost fluids and electrolytes.
  • Severe Cases: In instances of severe dehydration, intravenous fluid and electrolyte replacement may be necessary to stabilize the patient.
  • Antibiotics: Antibiotic therapy is not required for food poisoning caused by Bacillus cereus, as the illness is due to the ingestion of preformed toxins rather than a bacterial infection.

2. Invasive Disease

• Antibiotic Therapy:
  • Effective Antibiotics:
    • Clindamycin: Effective in treating various invasive infections caused by Bacillus cereus.
    • Erythromycin: Another antibiotic that can be used for treating infections.
    • Vancomycin: Useful in managing severe infections, especially those resistant to other antibiotics.
    • Aminoglycosides: Includes drugs such as gentamicin, effective in treating some Bacillus cereus infections.
    • Tetracycline: Effective against Bacillus cereus in certain clinical situations.
  • Antibiotic Resistance:
    • Penicillin: Bacillus cereus is resistant to penicillin, thus it is not recommended for treatment.
    • Trimethoprim: Resistance to trimethoprim also means it should not be used for treating Bacillus cereus infections.

What are the prevention and control measures for Bacillus cereus?

1. Food Safety Practices

• Temperature Control:
  • Food Holding Temperatures: To prevent the growth of Bacillus cereus, avoid holding meat and vegetables at temperatures between 10°C and 45°C (50°F and 113°F) for extended periods. This temperature range is conducive to bacterial growth.
  • Rice Storage: Cooked rice should be promptly refrigerated if not consumed immediately. Holding cooked rice at room temperature for prolonged periods allows spores to germinate and produce enterotoxins.
• Cooking and Heat Treatment:
  • Wet Heat: To effectively destroy Bacillus cereus spores, use wet heat methods such as poaching, simmering, boiling, braising, stewing, or pot roasting. Ensure that the food is heated to 121°C (250°F) for at least 5 minutes at the coldest spot.
  • Dry Heat: For dry heat methods like grilling, broiling, baking, roasting, or sautéing, maintain a temperature of 120°C (248°F) for 1 hour to kill spores on the exposed surface.
• Contamination Prevention:
  • Avoid Alcohol: Bacillus cereus is resistant to alcohol and can survive in alcohol-soaked swabs and distilled liquors. Therefore, alcohol-based disinfection may not be effective against this bacterium.

2. Management in Clinical and Environmental Settings

• Food Handling:
  • Proper Hygiene: Implement good hygiene practices in food preparation and handling to minimize contamination. This includes thorough washing of hands, utensils, and surfaces.
  • Avoiding Cross-Contamination: Ensure that raw and cooked foods are kept separate to prevent cross-contamination.
• Special Conditions:
  • Immunocompromised Patients: For individuals who are immunocompromised or have undergone surgery, adherence to stringent infection control measures is crucial. This includes using sterile equipment and ensuring proper wound care to prevent infections.

3. Research and Development

• Antimicrobial Agents:
  • β-Cypermethrin: Research indicates that β-cypermethrin, an antimicrobial agent, can break down under the action of certain Bacillus cereus strains, such as the GW-01 strain. This suggests potential applications for β-cypermethrin in controlling Bacillus cereus, though its effectiveness varies with concentration.

What are the symptoms of Bacillus cereus food poisoning?

There are two primary kinds of B. cereus that can cause food safety issues. The first is responsible for diarrhoea (diarrhoeal-type) and the second one can cause nausea (vomiting-type).

The diarrhoeal type in B. cereus is a harmful substances within the small intestinal. This means that one is susceptible to suffering from diarrhoea, if they consume food items that contain high levels of the bacteria or the spores (which could later transform to bacteria).

Spores from this type of bacteria are found in various types of food like milk and meat. Researchers have discovered that certain foods like soups, sauces or salads (with raw vegetables) typically contain an abundance of B. cereus. Dry plant products, like spices, herbs and cereals also have various levels of the bacteria. If these items are added to other kinds of food items or are made into drinking water, the spores can become bacteria and then grow in large quantities if the food is not consumed in a timely manner.

The vomiting form that is a result of B. cereus can cause toxic substances in food. It is the reason that a person might experience nausea, vomiting and abdominal cramps when he or she consumes food that is contaminated. This kind of bacteria is typically associated with foods high in starch, like pasta, rice and noodles. The bacteria are able to multiply quickly and create toxins in foods if they are kept within”the “temperature dangerous zone” for a long time. In this scenario the quantity of toxins consumed will affect intensity of the symptoms experienced by the affected person.

For healthy individuals generally, they only experience mild discomfort and generally get better on their own within one day.

References

• Bailey and Scott’s Diagnostic Microbiology.
• McDowell RH, Sands EM, Friedman H. Bacillus Cereus. [Updated 2023 Jan 23]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK459121/
• Bottone EJ. Bacillus cereus, a volatile human pathogen. Clin Microbiol Rev. 2010 Apr;23(2):382-98. doi: 10.1128/CMR.00073-09. PMID: 20375358; PMCID: PMC2863360.
• http://www.bccdc.ca/health-info/diseases-conditions/bacillus-cereus
• https://www.webmd.com/food-recipes/food-poisoning/what-is-bacillus-cereus
• https://textbookofbacteriology.net/Bacillus_4.html