The growth of four Bacillus cereus strains producing
diarrhoeal toxin at
32°C (F4433/73 and 29.155, isolated on the occasion of foodborne
outbreaks, and
F4581/76L and F4581/76R, two variants of a clinical strain),
a weakly toxigenic
strain isolated in routine analysis of food (3505M) and an emetic isolate
(F3502/73)
was investigated at low temperature. Biomass was determined by protein
assay.
Generation times were: for strain F3502/73, which grew at [ges ]12°C,
8·71 h (at 12°C);
for other strains, which grew at [ges ]10°C, 10·2 to ∼18·9
h
(at 10°C). Toxin
production during growth was evaluated by a commercial kit (Oxoid) and
by a
toxicity test on Chinese hamster ovary cells. Strains
F4433/73 and F4581/76,
secreting high levels of diarrhoeal toxin during the exponential phase
at 32°C,
produced high levels of toxicity at 10°C until the stationary phase.
Strain
29.155 had
decreased toxin production at 10°C. Toxicities for cellular extracts
remained low
when compared with culture filtrates. A correlation was found between the
toxicity
values given by the two detection methods tested, and the suitability of
both
methods for the detection of potential poisoning isolates is discussed.