A NEW FORMULA FOR AN ALTERNATIVE CULTURE-MEDIUM, WITHOUT ANTIBIOTICS,FOR ISOLATION AND PRESUMPTIVE QUANTIFICATION OF BACILLUS-CEREUS IN FOODS

This paper describes a new formula for a selective/indicator culture m edium, without antibiotics, that can be used for of Bacillus cereus in foods and other of colonies of presumptive quantification products. T his medium, VRM, as well as indicating hydrolysis of egg lecithin, als o enables a clear identification of colonies of B. cereus and the rela ted species Bacillus thuringiensis, not only by morphology, but also b y color. Bacillus megaterium, on the other hand, is inhibited in VRM, because the medium contains a combination of Tris and the oxidation/re duction resazurin. Without both these substances, inhibition is not ob served. These compounds maintained at pH 8.2 +/- 0.1 in a formula that also contains tryptone, egg yolk and salts - inhibit or delay the gro wth of other microorganisms found in foods. Compared with the traditio nal Mossel medium (MYP), our medium has two distinct advantages: the n on-requirement of antibiotics such as polymyxin B and reduced complexi ty in terms of production in the laboratory.