Yes, Bacillus cereus can be a pathogenic organism.
Because most members of the genus Bacillus are saprophytic bacteria
they are not usually considered as pathogens but most of us have
heard of anthrax caused by Bacillus anthracis.
B. cereus is better known as a food poisoning organism causing either
emesis (puking) (associated with rice) or diarrhoeae (associated with
meats). These are both probably intoxications rather than
infections. That is the toxic proteins the bacteria makes and
secretes are made during bacterial growth in the contaminated food
and its the ingestion of the toxin, not the bacteria, that causes the
food poisoning (this explains the often rapid onset of the symptoms).
The difference in the types of poisoning may be associated with
different toxins that different strains produce. Yes, different
strains of the same bacterial species can make very different toxins
(see Staphylococcus aureus).
It's not clear to what extent the presence of B. cereus in the stool
is associated with disease as it can be isolated from the feces of
healthy people. Because B. cereus is intrinsically resistant to
penicillin antibiotic therapy may select for increased numbers of
that bug in the patient's stool, whether this leads to any diarrheal
disease (like what happens with Clostridia difficile) I do not know.
By the way ATCC6633 is a strain of B. subtilis (not B. cereus).
Steve Projan
Wyeth-Ayerst Research
