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Bacillus cereus
B. cereus colonies 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 bacterium. Some strains are harmful to humans and cause foodborne illness, while other strains can be beneficial as probiotics for animals.[1] B. cereus bacteria are facultative anaerobes, and like other members of the genus Bacillus can produce protective endospores.

Symbiosis

B. cereus competes with other microorganisms such as Salmonella and Campylobacter in the gut, so its presence reduces the numbers of those microorganisms. In food animals such as chickens[2], rabbits[3] and pigs,[4] some harmless strains of B. cereus are used as a probiotic feed additive to reduce Salmonella in the intestines and cecum. This improves the animals' growth as well as food safety for humans who eat their meat.

Pathogenesis

B. cereus is responsible for a minority of foodborne illnesses (2–5%), causing severe nausea, vomiting and diarrhea.[5] Generally speaking, Bacillus foodborne illnesses occur due to survival of the bacterial endospores when food is improperly cooked.[6] This problem is compounded when food is then improperly refrigerated, allowing the endospores to germinate.[7] Bacterial growth results in production of enterotoxins, one of which is highly resistant to heat and to pH between 2 and 11;[8] ingestion leads to two types of illness, diarrheal and emetic (vomiting) syndrome.[9]

  • The diarrheal type is associated with a wide-range of foods, has an 8- to 16.5-hour incubation time and is associated with diarrhea and gastrointestinal pain. Also known as the long-incubation form of B. cereus food poisoning, it might be difficult to differentiate from poisoning caused by Clostridium perfringens.[8]
  • The emetic form is commonly caused by rice that is not cooked for a time and temperature sufficient to kill any spores present, then improperly refrigerated. It can produce a toxin which is not inactivated by later reheating. This form leads to nausea and vomiting 1–5 hours after consumption. It can be difficult to distinguish from other short-term bacterial foodborne pathogens such as Staphylococcus aureus).[8]

If rice is cooked at, or over 100 degrees Celsius for 20 minutes or more bacillus cereus cannot survive, therefore eliminating possible food poisoning.

The diarrhetic syndromes observed in patients is thought to stem from the three toxins Hemolysin BL Hbl, Nonhemolytic Enterotoxin Nhe and Cytotoxin K CytK [10]. The nhe/hbl/cytK genes are located on the chromosome of the bacteria, transcription of these genes is controlled by PlcR. These genes occur as well in the toxonomically related B. thuringensis and B. anthracis. These enterotoxins are all produced in the small intestine of the host, thus thwarting the issue of digestion by host endogenous enzymes. The Hbl and Nhe toxins are pore-forming toxins closely related to ClyA of E. coli, in conformation known as "barrel protein" as they can insert into cellular membranes and cause pores. The effect is loss of cellular membrane potential and eventually cell death. CytK is as well a pore-forming protein more related to other hemolysins.

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 is a dodecadepsipeptide (twelve-cyclic-peptide as it contains 3 repeats of 4 amino acids, similar to Valinomycin produced by Streptomyces griseus) produced by non-ribosomal peptide synthesis (NRPS), which is somewhat unusual in itself. Cereulide is believed to activate 5-HT3 (serotonin) receptors leading to increased afferent vagal stimulation.[11] It was shown independently by two research groups to be encoded on a plasmid, which is called pCERE01[12] or pBCE4810.[13] 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.

B. cereus is also known to cause people to have skin infections that can be quite lengthy, difficult to eradicate, and damaging, though less aggressive than the more notorious necrotizing fasciitis. B. cereus can also cause keratitis.[14]

References

  1. ^ Ryan KJ; Ray CG (editors) (2004). Sherris Medical Microbiology (4th ed.). McGraw Hill. ISBN 0-8385-8529-9.  
  2. ^ Vilà, B; A. Fontgibell, I. Badiola, E. Esteve-Garcia, G. Jiménez, M. Castillo and J. Brufau (2009). "Reduction of Salmonella enterica var. Enteritidis colonization and invasion by Bacillus cereus var. toyoi inclusion in poultry feeds". Poultry Science (HighWire Press) 88 (55): 975–9. doi:10.3382/ps.2008-00483. http://ps.fass.org/cgi/content/full/88/5/975. Retrieved 14 May 2009.  
  3. ^ Bories, Georges; Paul Brantom, Joaquim Brufau de Barberà, Andrew Chesson, Pier Sandro Cocconcelli, Bogdan Debski, Noël Dierick, Jürgen Gropp, Ingrid Halle, Christer Hogstrand, Joop de Knecht, Lubomir Leng, Sven Lindgren, Anne-Katrine Lundebye Haldorsen, Alberto Mantovani, Miklós Mézes, Carlo Nebbia, Walter Rambeck, Guido Rychen, Atte von Wright and Pieter Wester (9 December 2008). Safety and efficacy of the product Toyocerin (Bacillus cereus var. toyoi) as feed additive for rabbit breeding does - Scientific Opinion of the Panel on Additives and Products or Substances used in Animal Feed. European Food Safety Authority. EFSA-Q-2008-287. http://www.efsa.europa.eu/cs/BlobServer/Scientific_Opinion/feedap_op_ej913_toyocerin_en,3.pdf?ssbinary=true. Retrieved 14 May 2009.  
  4. ^ Bories, Georges; Paul Brantom, Joaquim Brufau de Barberà, Andrew Chesson, Pier Sandro Cocconcelli, Bogdan Debski, Noël Dierick, Anders Franklin, Jürgen Gropp, Ingrid Halle, Christer Hogstrand, Joop de Knecht, Lubomir Leng, Anne-Katrine Lundebye Haldorsen, Alberto Mantovani, Miklós Mézes, Carlo Nebbia, Walter Rambeck, Guido Rychen, Atte von Wright and Pieter Wester (EFSA-Q-2006-037). Opinion of the Scientific Panel on Additives and Products or Substances used in Animal Feed on the safety and efficacy of the product Toyocerin (Bacillus cereus var. Toyoi) as a feed additive for sows from service to weaning, in accordance with Regulation (EC) No 1831/2003. European Food Safety Authority. http://www.efsa.europa.eu/cs/BlobServer/Scientific_Opinion/feedap_op_ej458_toyocerin_sows_en.pdf?ssbinary=true. Retrieved 14 May 2009.  
  5. ^ Kotiranta A, Lounatmaa K, Haapasalo M (2000). "Epidemiology and pathogenesis of Bacillus cereus infections". Microbes Infect 2 (2): 189–98. doi:10.1016/S1286-4579(00)00269-0. PMID 10742691.  
  6. ^ 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.  
  7. ^ 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. doi:10.1023/A:1002706906154. PMID 10959569.  
  8. ^ a b c "Bacillus cereus". Todar's Online Textbook of Bacteriology. http://textbookofbacteriology.net/B.cereus.html. Retrieved 2009-09-19.  
  9. ^ 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. doi:10.1002/mnfr.200400055. PMID 15538709.  
  10. ^ Enterotoxigenic Profiles of Food-Poisoning and Food-Borne Bacillus cereus Strains Marie-Hélène Guinebretière,* Véronique Broussolle, and Christophe Nguyen-TheInstitut National de la Recherche Agronomique, UMR A408 Sécurité et Qualité des Produits d'Origine Végétale, INRA, Domaine Saint-Paul, Site Agroparc, F-84914 Avignon Cedex 9, France. PMCID: PMC120679
  11. ^ Agata N, Ohta M, Mori M, Isobe M (1995). "A novel dodecadepsipeptide, cereulide, is an emetic toxin of Bacillus cereus.". FEMS Microbiol Lett 129 (1): 17–20. PMID 7781985.  
  12. ^ 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. doi:10.1099/mic.0.28069-0. PMID 16000702.  
  13. ^ 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): 20. doi:10.1186/1471-2180-6-20. PMID 16512902.  
  14. ^ Pinna A, Sechi LA, Zanetti S, et al. (October 2001). "Bacillus cereus keratitis associated with contact lens wear". Ophthalmology 108 (10): 1830–4. doi:10.1016/S0161-6420(01)00723-0. PMID 11581057. http://linkinghub.elsevier.com/retrieve/pii/S0161-6420(01)00723-0.  
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Wikispecies

Up to date as of January 23, 2010

From Wikispecies

Taxonavigation

Main Page
Superregnum: Bacteria
Regnum: Bacteria
Phylum: Firmicutes
Classis: Bacilli
Ordo: Bacillales
Familia: Bacillaceae
Genus: Bacillus
Species group: Bacillus cereus group
Species: Bacillus cereus
Strain: Bacillus cereus ATCC 10987 - Bacillus cereus ATCC 14579 - Bacillus cereus E33L -

References


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