Bacillus cereus is an aerobic sporeformer commonly found in raw and process
ed foods. Foodborne illnesses associated with this pathogen are caused prim
arily by consumption of cooked foods with inadequate refrigeration. Mannito
l-egg yolk-polymyxin (MYP) agar is widely used for isolation and enumeratio
n of the pathogen. in the present study, a new selective medium, which cont
ains a chromogenic substrate (5-bromo-4-chloro-3-indoxyl-myo-inositol-1-pho
sphate) for the detection of phosphatidylinositol-specific phospholipase C
in B, cereus/B. thuringiensis organisms, was evaluated and compared to MYP
Twenty B. cereus strains four B. thuringiensis strains 95 other Gram-positi
ve and 14 Gram-negative organisms were examined on BCM (R) B. cereus/B. thu
ringiensis (BioSynth) and MYP agar. Only B, cereus and B. thuringiensis for
med large (2-7mm), turquoise fiat colonies +/- turquoise halos on BCM (R) a
fter incubation for 24 h at 35 degrees C, while other Bacillus spp formed w
hite, 1-2 mm colonies or were inhibited Some Listeria strains formed < 1-mm
colonies white or turquoise on the medium Of the Gram-positive non-B, cere
us/B. thuringiensis organisms tested growth of > 50% was inhibited on BCM (
R) compared to < 1 % on MYP. No significant difference (P > 0.05) was obser
ved on the two media in the recovery of B, cereus strains from foods inocul
ated or naturally contaminated with the organisms. However colony enumerati
on and isolation were easier on BCM (R) than on MYP because of higher selec
tivity and formation of discrete, non-coalescing colonies. Ribotyping (Ribo
printer (R) Microbial identification System Qualicon) of five randomly sele
cted food isolates identified three B. cereus and two B. thuringiensis stra
ins. Agar plates were stable for > 3 months at 2-5 degrees C. (C) 2001 Acad
emic Press.