BACILLUS CEREUS

'''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.

Contents

Pathogenesis

References

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]
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★ 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''. ''Bacillus cereus''
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★ 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'').
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 ^[6] or pBCE4810 ^[7]. 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. Sherris Medical Microbiology, Ryan KJ; Ray CG (editors), , , McGraw Hill, 2004, ISBN 0-8385-8529-9
2. Epidemiology and pathogenesis of ''Bacillus cereus'' infections, Kotiranta A, Lounatmaa K, Haapasalo M, , , Microbes Infect, 2000
3. Bacillus. ''In:'' Baron's Medical Microbiology ''(Barron S ''et al'', eds.), Turnbull PCB, , , Univ of Texas Medical Branch, 1996, (via NCBI Bookshelf) ISBN 0-9631172-1-1
4. Prevalence and expression of enterotoxins in ''Bacillus cereus'' and other ''Bacillus'' spp., a literature review, McKillip JL, , , Antonie Van Leeuwenhoek, 2000
5. ''Bacillus cereus'', the causative agent of an emetic type of food-borne illness, Ehling-Schulz M, Fricker M, Scherer S, , , Mol Nutr Food Res, 2004
6. The cereulide genetic determinants of emetic ''Bacillus cereus'' are plasmid-borne., Hoton FM, Andrup L, Swiecicka I, Mahillon J, , , Microbiology, 2005
7. Cereulide synthetase gene cluster from emetic ''Bacillus cereus'': structure and location on a mega virulence plasmid related to ''Bacillus anthracis'' toxin plasmid pXO1., Ehling-Schulz M, Fricker M, Grallert H, Rieck P, Wagner M, Scherer S, , , BMC Microbiol, 2006