Bacillus cereus

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Bacillus cereus
Bacillus cereus 01.png
B. cereus colonies on a sheep-blood agar plate
Scientific classification
Kingdom: Bacteria
Phylum: Firmicutes
Class: Bacilli
Order: Bacillales
Family: Bacillaceae
Genus: Bacillus
Species: B. cereus
Binomial name
Bacillus cereus
Frankland & Frankland 1887

Bacillus cereus is an endemic, soil-dwelling, Gram-positive, rod-shaped, motile, beta hemolytic bacterium. Some strains are harmful to humans and cause foodborne illness, while other strains can be beneficial as probiotics for animals.[1] It is the cause of "fried rice syndrome", as the bacteria are classically contracted from fried rice dishes that have been sitting at room temperature for hours (such as at a buffet).[2] B. cereus bacteria are facultative anaerobes, and like other members of the genus Bacillus, can produce protective endospores. Its virulence factors include cereolysin and phospholipase C.

Symbiosis[edit]

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,[3] rabbits[4] and pigs,[5] 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[edit]

B. cereus is responsible for a minority of foodborne illnesses (2–5%), causing severe nausea, vomiting, and diarrhea.[6] Bacillus foodborne illnesses occur due to survival of the bacterial endospores when food is improperly cooked.[7] Cooking temperatures less than or equal to 100°C (212°F) allow some B. cereus spores to survive.[8] This problem is compounded when food is then improperly refrigerated, allowing the endospores to germinate.[9] Cooked foods not meant for either immediate consumption or rapid cooling and refrigeration should be kept at temperatures below 10°C or above 50°C (50°F and 122°F).[8] Germination and growth generally occur between 10°C and 50°C,[8] though some strains are psychrotrophic.[10] Bacterial growth results in production of enterotoxins, one of which is highly resistant to heat and acids (pH levels between 2 and 11);[11] ingestion leads to two types of illness, diarrheal and emetic (vomiting) syndrome.[12]

  • The diarrheal type is associated with a wide range of foods, has an 8.0- to 16-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.[11]
  • The 'emetic' form is commonly caused by rice cooked for a time and temperature insufficient to kill any spores present, then improperly refrigerated. It can produce a toxin, cereulide, which is not inactivated by later reheating. This form leads to nausea and vomiting one to five hours after consumption. It can be difficult to distinguish from other short-term bacterial foodborne toxins such as Staphylococcus aureus.[11]

The diarrhetic syndromes observed in patients are thought to stem from the three toxins: hemolysin BL (Hbl), nonhemolytic enterotoxin (Nhe) and cytotoxin K (CytK).[13] The nhe/hbl/cytK genes are located on the chromosome of the bacteria. Transcription of these genes is controlled by PlcR. These genes occur in the taxonomically related B. thuringiensis and B. anthracis, as well. These enterotoxins are all produced in the small intestine of the host, thus thwarting digestion by host endogenous enzymes. The Hbl and Nhe toxins are pore-forming toxins closely related to ClyA of E. coli. The proteins exhibit a conformation known as "beta-barrel" that can insert into cellular membranes due to a hydrophobic exterior, thus creating pores with hydrophilic interiors. The effect is loss of cellular membrane potential and eventually cell death. CytK is a pore-forming protein more related to other hemolysins.

The timing of the toxin production was previously thought to be possibly responsible for the two different courses of disease, but in fact the emetic syndrome is caused by a toxin, cereulide, found only in emetic strains and is not part of the "standard toolbox" of B. cereus. Cereulide is a cyclic polypeptide containing three repeats of four amino acids: D-oxy-Leu—D-Ala—L-oxy-Val—L-Val (similar to valinomycin produced by Streptomyces griseus) produced by nonribosomal peptide synthesis. Cereulide is believed to bind to 5-hydroxytryptamine 3 (5-HT3) serotonin receptors, activating them and leading to increased afferent vagus nerve stimulation.[14] It was shown independently by two research groups to be encoded on multiple plasmids: pCERE01[15] or pBCE4810.[16] Plasmid pBCE4810 shares homology with the Bacillus anthracis virulence plasmid pXO1, which encodes the anthrax toxin. Periodontal isolates of B. cereus also possess distinct pXO1-like plasmids. Like most of cyclic peptides containing nonproteogenic amino acids, cereulid is resistant to heat, proteolysis, and acid conditions.[17]

B. cereus is also known to cause difficult-to-eradicate chronic skin infections, though less aggressive than necrotizing fasciitis. B. cereus can also cause keratitis.[18]

Diagnosis[edit]

In case of foodborne illness, the diagnosis of B. cereus can be confirmed by the isolation of more than 105 B. cereus organisms per gram from epidemiologically implicated food, but such testing is often not done because the illness is relatively harmless and usually self-limiting.[19]

Prognosis[edit]

Most emetic patients recover within six to 24 hours,[12] but in some cases, the toxin can be fatal.[20][21][22][23][24]

References[edit]

  1. ^ Ryan KJ; Ray CG (editors) (2004). Sherris Medical Microbiology (4th ed.). McGraw Hill. ISBN 0-8385-8529-9. 
  2. ^ Asaeda, Glenn; Gilbert Caicedow; Christopher Swanson (December 2005). "Fried Rice Syndrome". Journal of Emergency Medical Services 30 (12): 30–32. doi:10.1016/S0197-2510(05)70258-8. ISSN 0197-2510. Retrieved 13 September 2011. 
  3. ^ 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. PMID 19359685. Archived from the original on 29 April 2009. Retrieved 14 May 2009. 
  4. ^ 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. Retrieved 14 May 2009. 
  5. ^ 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. Retrieved 14 May 2009.  Check date values in: |date= (help)
  6. ^ 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. 
  7. ^ Turnbull PCB (1996). Bacillus. In: Baron's Medical Microbiology (Barron S et al., eds.) (4th ed.). Univ of Texas Medical Branch. ISBN 0-9631172-1-1. (via NCBI Bookshelf). 
  8. ^ a b c Roberts, T. A.; Baird-Parker, A. C.; Tompkin, R. B. (1996). Characteristics of microbial pathogens. London: Blackie Academic & Professional. p. 24. ISBN 0-412-47350-X. Retrieved 25 November 2010. 
  9. ^ 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. 
  10. ^ Davis, Judi Ratliff; Lawley, Richard; Davis, Judy; Laurie Curtis (2008). The food safety hazard guidebook. Cambridge, UK: RSC Pub. p. 17. ISBN 0-85404-460-4. Retrieved 25 November 2010. 
  11. ^ a b c "Bacillus cereus". Todar's Online Textbook of Bacteriology. Retrieved 19 September 2009. 
  12. ^ a b 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. 
  13. ^ Guinebretière MH, Broussolle V, Nguyen-The C (August 2002). "Enterotoxigenic Profiles of Food-poisoning and Food-borne Bacillus cereus Strains". J. Clin. Microbiol. 40 (8): 3053–6. doi:10.1128/JCM.40.8.3053-3056.2002. PMC 120679. PMID 12149378. 
  14. ^ 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. doi:10.1016/0378-1097(95)00119-P. PMID 7781985. 
  15. ^ 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. 
  16. ^ 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. doi:10.1186/1471-2180-6-20. PMC 1459170. PMID 16512902. 
  17. ^ Stenfors Arnesen LP, Fagerlund A, Granum PE (2008). "From soil to gut: Bacillus cereus and its food poisoning toxins". FEMS Microbiol Rev. 32 (4): 579–606. doi:10.1111/j.1574-6976.2008.00112.x. PMID 18422617. 
  18. ^ 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. 
  19. ^ Bacillus cereus Food Poisoning Associated with Fried Rice at Two Child Day Care Centers from Morbidity and Mortality Weekly Report from Centers for Disease Control and Prevention. 18 March 1994 / Vol. 43 / No. 10 U.S.
  20. ^ Takabe F, Oya M (1976). "An autopsy case of food poisoning associated with Bacillus cereus". ForensicSci 7 (2): 97–101. 
  21. ^ Mahler H et al. (1997). "Fulminant liver failure in association with the emetic toxin of Bacillus cereus". N Engl J Med 336 (16): 1142–1148. doi:10.1056/NEJM199704173361604. PMID 9099658. 
  22. ^ Dierick K et al. (2005). "Fatal family outbreak of Bacillus cereus-associated food poisoning". J Clin Microbiol 43 (8): 4277–4279. doi:10.1128/JCM.43.8.4277-4279.2005. 
  23. ^ Shiota, M et al. (2010). "Rapid Detoxification of Cereulide in Bacillus cereus Food Poisoning". Pediatrics 125 (4): e951–e955. doi:10.1542/peds.2009-2319. 
  24. ^ Naranjo, M et al. (2011). "Sudden Death of a Young Adult Associated with Bacillus cereus Food Poisoning". J Clin Microbiol 49 (12): 4379–4381. doi:10.1128/JCM.05129-11. 

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