Bacillus cereus
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| B. cereus on sheep blood agar plate. B. cereus on sheep blood agar plate.
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| Bacillus cereus Frankland & Frankland 1887 |
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Bacillus cereus is an endemic, soil-dwelling, Gram-positive, rod shaped, beta hemolytic bacteria that causes foodborne illness.[1] It is the cause of "Fried Rice Syndrome". B. cereus bacteria are facultative aerobes, and like other members of the genus Bacillus can produce protective endospores.
Pathogenesis
B. cereus is responsible for a minority of foodborne illnesses (2–5%). It is known to create heavy nausea, vomiting, and abdominal periods. [2] Generally speaking, Bacillus foodborne illnesses occur due to survival of the bacterial spores when food is improperly cooked.[3] This problem is compounded when food is then improperly refrigerated, allowing the spores to germinate.[4] Bacterial growth results in production of enterotoxin, and ingestion leads to two types of illness, diarrheal and emetic syndrome.[5]
- The diarrheal type is associated with a wide-range of foods, has an 8–16 hour incubation time and is associated with diarrhea and gastrointestinal pain. Also know as the long-incubation form of B. cereus food poisoning, it can be difficult to differentiate from poisoning caused by Clostridium perfringens.[6]
- In the emetic form, cooked rice that is improperly refrigerated is the most common cause, leading to nausea and vomiting 1–5 hours after consumption. This form can be difficult to distinguish from other short-term bacterial foodborne pathogens (e.g. Staphylococcus aureus).[6]
It was previously thought that the timing of the toxin production might be responsible for the two different types, but in fact the emetic syndrome is caused by a toxin called cereulide that is found only in emetic strains and is not part of the 'standard toolbox' of B. cereus. Cereulide a dodecadepsipeptide produced by non-ribosomal peptide synthesis (NRPS), which is somewhat unusual in itself. It was shown independently by two research groups to be encoded on a plasmid, which is called pCERE01 [7] or pBCE4810 [8]. Interestingly, this plasmid shares a common backbone with the virulence plasmid pXO1, which encodes the anthrax toxin genes in B. anthracis, but with a different pathogenicity island. Periodontal isolates of B. cereus also possess distinct pXO1-like plasmids.
Gallery
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![A closer view of PHIL 12377, this photograph depicts the colonial morphology displayed by Gram-positive Bacillus cereus bacteria, which was grown on a medium of sheep’s blood agar (SBA), for a 24 hour time period, at a temperature of 37°C. From Public Health Image Library (PHIL). [9]](/images/f/fa/Bacillus_cereus01.jpeg)
A closer view of PHIL 12377, this photograph depicts the colonial morphology displayed by Gram-positive Bacillus cereus bacteria, which was grown on a medium of sheep’s blood agar (SBA), for a 24 hour time period, at a temperature of 37°C. From Public Health Image Library (PHIL). [9]
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![This photograph depicts the colonial morphology displayed by Gram-positive Bacillus cereus bacteria, which was grown on a medium of sheep’s blood agar (SBA), for a 24 hour time period, at a temperature of 37°C. From Public Health Image Library (PHIL). [9]](/images/c/cc/Bacillus_cereus02.jpeg)
This photograph depicts the colonial morphology displayed by Gram-positive Bacillus cereus bacteria, which was grown on a medium of sheep’s blood agar (SBA), for a 24 hour time period, at a temperature of 37°C. From Public Health Image Library (PHIL). [9]
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![Bacillus cereus showing hemolysis on sheep blood agar. From Public Health Image Library (PHIL). [9]](/images/6/61/Bacillus_cereus03.jpeg)
Bacillus cereus showing hemolysis on sheep blood agar. From Public Health Image Library (PHIL). [9]
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![Bacillus cereus showing hemolysis on sheep blood agar. From Public Health Image Library (PHIL). [9]](/images/f/fa/Bacillus_cereus04.jpeg)
Bacillus cereus showing hemolysis on sheep blood agar. From Public Health Image Library (PHIL). [9]
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![Blood agar and bicarbonate agar plate cultures of Bacillus cereus. From Public Health Image Library (PHIL). [9]](/images/6/6a/Bacillus_cereus05.jpeg)
Blood agar and bicarbonate agar plate cultures of Bacillus cereus. From Public Health Image Library (PHIL). [9]
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![Sheep blood agar plate culture of Bacillus anthracis and Bacillus cereus. From Public Health Image Library (PHIL). [9]](/images/3/3b/Bacillus_cereus06.jpeg)
Sheep blood agar plate culture of Bacillus anthracis and Bacillus cereus. From Public Health Image Library (PHIL). [9]
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![Bacillus cereus. Gram stain. From Public Health Image Library (PHIL). [9]](/images/2/22/Bacillus_cereus07.jpeg)
Bacillus cereus. Gram stain. From Public Health Image Library (PHIL). [9]
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![Bacillus cereus. Leifson flagella stain. From Public Health Image Library (PHIL). [9]](/images/d/d0/Bacillus_cereus08.jpeg)
Bacillus cereus. Leifson flagella stain. From Public Health Image Library (PHIL). [9]
![A closer view of PHIL 12377, this photograph depicts the colonial morphology displayed by Gram-positive Bacillus cereus bacteria, which was grown on a medium of sheep’s blood agar (SBA), for a 24 hour time period, at a temperature of 37°C. From Public Health Image Library (PHIL). [9]](/index.php/File:Bacillus_cereus01.jpeg)
![This photograph depicts the colonial morphology displayed by Gram-positive Bacillus cereus bacteria, which was grown on a medium of sheep’s blood agar (SBA), for a 24 hour time period, at a temperature of 37°C. From Public Health Image Library (PHIL). [9]](/index.php/File:Bacillus_cereus02.jpeg)
![Bacillus cereus showing hemolysis on sheep blood agar. From Public Health Image Library (PHIL). [9]](/index.php/File:Bacillus_cereus03.jpeg)
![Bacillus cereus showing hemolysis on sheep blood agar. From Public Health Image Library (PHIL). [9]](/index.php/File:Bacillus_cereus04.jpeg)
![Blood agar and bicarbonate agar plate cultures of Bacillus cereus. From Public Health Image Library (PHIL). [9]](/index.php/File:Bacillus_cereus05.jpeg)
![Sheep blood agar plate culture of Bacillus anthracis and Bacillus cereus. From Public Health Image Library (PHIL). [9]](/index.php/File:Bacillus_cereus06.jpeg)
![Bacillus cereus. Gram stain. From Public Health Image Library (PHIL). [9]](/index.php/File:Bacillus_cereus07.jpeg)
![Bacillus cereus. Leifson flagella stain. From Public Health Image Library (PHIL). [9]](/index.php/File:Bacillus_cereus08.jpeg)
Treatment
Antimicrobial therapy
- Bacillus cereus[10]
- (1) Food poisoning
- Preferred treatment: supportive therapy, hydration, and anti-emetics
- Note: Food poisoning caused by B. cereus is self-limited and antibiotic therapy is not recommended.
- (2) Bacteremia
- Preferred regimen: Vancomycin 15 mg/kg IV q12h.
- Alternative regimen: Clindamycin 600 mg IV q8h
- Note (1): Bacillus cereus often resistant to beta-lactams.
- Note (2): Uncommon, may complicate mixed infections including surgical wounds or infected necrotic tumors.
- Note (3): Source of pseudobacteremia is contaminated blood cultures, gloves, syringes, etc. Often transient bacteremia of no significance in intravenous drug user population.
- (3) Meningitis, brain abscess
- Preferred regimen: Vancomycin 15 mg/kg IV q12h.
- Alternative regimen: Clindamycin 600 mg IV q8h.
- Note (1): Blood culture isolates are mostly contaminates until proven otherwise, especially in intravenous drug user population.
- Note(2): Uncommon presentations, may complicate otitis, mastoiditis, neurosurgical procedures, and shunts.
- (4) Endophthalmitis
- Preferred regimen: Clindamycin 450 mcg intravitreal AND Gentamicin 400 mcg intravitreal OR Dexamethasone intravitreal AND Vancomycin 15 mg/kg IV q12h.
- Alternative regimen: Clindamycin 600 mg IV q8h
- Note (1): Prognosis for sight retention poor.
- Note (2): Rapid, massive destruction of vitreous/retina in intravenous drug user or posttraumatic with ringabscess within 48 hrs. Pathognomic Bacillus cereus panophthalmitis.
- Note (3): Early ophthalmological consultation, culture ocular fluids. Early vitrectomy and intravitreal antibiotics is advocated.
- Note (4): Ocular infections devastating and require quick intervention.
- Note (5): primary pathogen of post-traumatic , risk factor also intravenous drug use. May also cause keratitis, orbital abscess, conjunctivitis, dacryocystitis.
- (5) Endocarditis
- Preferred regimen: Vancomycin 15 mg/kg IV q12h OR Clindamycin 600 mg IV q8h.
- Note (1): Well-described but rare complication seen in intravenous drug user . Most blood cultures in intravenous drug user positive for bacillus are contaminates or represent transient bacteremia.
- Note (2): Evidence of valvular involvement should be sought by echocardiography to prove endocarditis. Tricuspid valve involvement most common. Course indolent.
- Note (3): Tricuspid valve endocarditis mostly indolent in nature.
- (6) Soft tissue
- Preferred regimen: Vancomycin 15 mg/kg IV q12h.
- Alternative regimen: Clindamycin 600 mg IV q8h.
- note: rare reports of fasciitis.
- (7) Pneumonia
- Preferred regimen: Vancomycin 15 mg/kg IV q12h.
- Alternative regimen: Clindamycin 600 mg IV q8h.
- Note: rare pathogen of compromised host. May mimic Bacillus anthracis-type presentation.
References
- ↑ Ryan KJ; Ray CG (editors) (2004). Sherris Medical Microbiology (4th ed. ed.). McGraw Hill. ISBN 0-8385-8529-9.
- ↑ Kotiranta A, Lounatmaa K, Haapasalo M (2000). "Epidemiology and pathogenesis of Bacillus cereus infections". Microbes Infect. 2 (2): 189–98. PMID 10742691.
- ↑ Turnbull PCB (1996). Bacillus. In: Baron's Medical Microbiology (Barron S et al, eds.) (4th ed. ed.). Univ of Texas Medical Branch. (via NCBI Bookshelf) ISBN 0-9631172-1-1.
- ↑ McKillip JL (2000). "Prevalence and expression of enterotoxins in Bacillus cereus and other Bacillus spp., a literature review". Antonie Van Leeuwenhoek. 77 (4): 393–9. PMID 10959569.
- ↑ Ehling-Schulz M, Fricker M, Scherer S (2004). "Bacillus cereus, the causative agent of an emetic type of food-borne illness". Mol Nutr Food Res. 48 (7): 479–87. PMID 15538709.
- ↑ 6.0 6.1 "Bacillus cereus". Todar's Online Textbook of Bacteriology. Retrieved 2006-04-10.
- ↑ Hoton FM, Andrup L, Swiecicka I, Mahillon J (2005). "The cereulide genetic determinants of emetic Bacillus cereus are plasmid-borne". Microbiology. 151 (7): 2121–4. PMID 16000702.
- ↑ Ehling-Schulz M, Fricker M, Grallert H, Rieck P, Wagner M, Scherer S (2006). "Cereulide synthetase gene cluster from emetic Bacillus cereus: structure and location on a mega virulence plasmid related to Bacillus anthracis toxin plasmid pXO1". BMC Microbiol. 6 (20). PMID 16512902.
- ↑ 9.0 9.1 9.2 9.3 9.4 9.5 9.6 9.7 "Public Health Image Library (PHIL)".
- ↑ Bartlett, John (2012). Johns Hopkins ABX guide : diagnosis and treatment of infectious diseases. Burlington, MA: Jones and Bartlett Learning. ISBN 978-1449625580.
References
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