Isolation and enumeration of Bacillus cereus from foods on a novel chromogenic plating medium

Citation
H. Peng et al., Isolation and enumeration of Bacillus cereus from foods on a novel chromogenic plating medium, FOOD MICROB, 18(3), 2001, pp. 231-238
Citations number
19
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Food Science/Nutrition
Journal title
FOOD MICROBIOLOGY
ISSN journal
0740-0020 → ACNP
Volume
18
Issue
3
Year of publication
2001
Pages
231 - 238
Database
ISI
SICI code
0740-0020(200106)18:3<231:IAEOBC>2.0.ZU;2-Q
Abstract
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.