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FOOD POISONING CAUSED BY
GRAM
POSITIVESPORE FORMING BACTERIA
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Bacillus cereus
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Introduction ofBacillus cereus
Considered a minor foodborne panthogen, but one thatis increasingly important.
Bacillus cereus disease is not notifiable.
B. cereus causes
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Characteristics of the Organisms
o Bacteria : aerobic rod shaped bacterium .
Bacillus
cereus
group
B.anthracis
B. thuringiensis
B. pseudomycoides
B. weihenstephanensis
B. mycoidesB. cereus
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o B. anthracis the most distinctive member of this group.
highly virulent pathogenicity.
notoriety as an agent for biological warfare.
o B. thuringiensis
natural bioinsecticide caused cases ofB. cereusfood poisoning.
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Environmental Sources
Present in soil at10^5 /g
Spread to cowsudders and into raw
milk
Survive milkpasteurization
Causing problems inmany milk
productions
osoil and growing plants.oB. cereus always problematic in dairy foods.
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Characteristics of Disease
Emetic toxin
Result : vomiting
Enterotoxin(s)
Result : diarrhea
2 typeB. cereus
foodborne illness
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o The incubation time ( >6 hours ; average ; 12 hours ) is too long for
diarrheal illness.o Enterotoxin(s) form in food B. cereus population is at least 100-
fold higher than that necessary.
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Dose
- Grew it to 4 x 10^6cells / ml
- Drank 200 ml of the
culture
13 hours later,abdominal pain and
watery diarrhea
B. cereus rangingfrom 200 to 10^9
organisms /g (or ml)
Total doseapproximately 5 x 10^4
cells/ml to 1 x 10^11cells/ml.
Enough toxin toproduce illness is
probably 10^5 and10^8 cells.
Food containing >10B.cereus organisms/g not
safe to eat.
Foodborne illness in Oslo, Norway ( from vanilla sauce )
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The Emetic Toxin
o the recent discovery that Hep-2 cells could detect the toxin has ledto its purification and structure determination.
o The emetic toxin is now named cereulide.
o Cereulide has 3 repeats of four amino acid and/or oxyacids
[ D-O-Leu-D-Ala-L-O-Val-L-Val ]3o Resistant to autoclaving, a wide range of pH values (2 to 11) and
digestion by proteases.
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Enterotoxins
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o Microslide diffusion tests are used to detectB. cereus diarrheagenicand staphylococcal enterotoxins.
o Antiserum to the toxin is put into well 1 and reference toxin is putinto well 3.
o Test sample are put into wells 2,4, and 5.
o When the antiserum and toxin diffuse from their respective wellsand meet, a precipatation line is formed.
o (A) Test where the food samples are negative but a line is formedwith the known enterotoxin.
o (B) Test where the sample in well 4 contains enterotoxin.
o (C) Photo of actual results, where samples in wells 2 and 4
(but no 5) are positive for toxin.
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Controlso Handling the food in the right way.
o Store the milk production between the temperature 4 to 8C.
o
Avoid cross
contamination.