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Bacillus cereus



Bacillus cereus

B. cereus on sheep blood agar plate.
Scientific classification
Kingdom: Bacteria
Phylum: Firmicutes
Class: Bacilli
Order: Bacillales
Family: Bacillaceae
Genus: Bacillus
Species: cereus
Binomial name
Bacillus cereus
Frankland & Frankland 1887

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.

Additional recommended knowledge

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.

References

  1. ^ Ryan KJ; Ray CG (editors) (2004). Sherris Medical Microbiology, 4th ed., McGraw Hill. ISBN 0-8385-8529-9. 
  2. ^ Kotiranta A, Lounatmaa K, Haapasalo M (2000). "Epidemiology and pathogenesis of Bacillus cereus infections". Microbes Infect 2 (2): 189-98. PMID 10742691.
  3. ^ Turnbull PCB (1996). Bacillus. In: Baron's Medical Microbiology (Barron S et al, eds.), 4th ed., Univ of Texas Medical Branch. (via NCBI Bookshelf) ISBN 0-9631172-1-1. 
  4. ^ 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.
  5. ^ 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. ^ a b Bacillus cereus. Todar's Online Textbook of Bacteriology. Retrieved on 2006-04-10.
  7. ^ 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.
  8. ^ 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.
 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Bacillus_cereus". A list of authors is available in Wikipedia.
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