BACILLUS CEREUS
A virtual case study.
A stroll in the park, a sprint to the bathroom.
• A family picnic with rice and
salad dishes amongst others.
• Many family members fell ill
with diarrheal and vomiting
symptoms within a few hours
of consuming food.
• It is determined that both the
rice and the salad were the
source of the illness.
• A faeces sample is processed
at QML for diagnostic study.
A profile of Bacillus cereus.
• A gram-positive endospore former, common in soil and
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present of many foods derived from ground based
agriculture such as rice and salad vegetables.
Produces vomiting symptoms from as little as half an hour
after inoculation.
Diarrheal symptoms after 6 hours.
A close similarity to the onset of the much more severe
clostridiosis has been noted.
Pathophysiology caused primarily by the production of
toxins.
Spore formation allows B.cereus to thrive in high heat
situations as well as some strains ability to continue
activity under refrigeration.
The diagnostic pathway of Bacillus cereus
Appearance of B.cereus on PEMBA agar.
http://pages.usherbrooke.ca/biomedias/cultures_microbio.htm
• Note the motile appearance of the colonies.
Some confirmatory tests
• Left – a motile strain of Bacillus
lentimorbus.
• Right – a non motile colony
growth.
The catalase test.
http://ericaandkevin.pbworks.com/w/page/5827086/Gram%20Stain%20and%20Other%20Tests
The future of laboratory diagnosis.
• The Bacillus genus is very
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genetically conserved, even the
16S ribosomal DNA sequences.
It is important to distinguish
between pathogenic and
commensal strains.
Current methodology is unable to
do this,.
The molecular revolution has
made this a viable future routine
form of diagnostic.
The toxin profile of the strain is the
most important.
Phylogenic tools.
References
• Fatal Family Outbreak of Bacillus cereus-Associated Food Poisoning Katelijne et.al J. Clin.
Microbiol. August 2005 43:8 4277-4279; doi:10.1128/JCM.43.8.4277-4279.2005
• Ehling-Schulz M and Messelhäusser U (2013) Bacillus “next generation” diagnostics: moving from
detection toward subtyping and risk-related strain profiling. Front. Microbiol. 4:32
• Bacteriological Analytical Manual Chapter 14 Bacillus cereus 2012 Sandra M. Tallent et.al
http://www.fda.gov/Food/FoodScienceResearch/LaboratoryMethods/ucm070875.htm