A new formula for an alternative culture medium, without antibiotics, for isolation and presumptive quantification of bacillus cereus in foods

Abstract

This paper describes a new formula for a selective/indicator culture medium, without antibiotics, that can be used for of Bacillus cereus in foods and other of colonies of presumptive quantification products. This medium, VRM, as well as indicating hydrolysis of egg lecithin, also enables a clear identification of colonies of B. cereus and the related species Bacillus thuringiensis, not only by morphology, but also by color. Bacillus megaterium, on the other hand, is inhibited in VRM, because the medium contains a combination of Tris and the oxidation/reduction resazurin. Without both these substances, inhibition is not observed. These compounds maintained at pH 8.2 + 0.1 in a formula that also contains tryptone, egg yolk and salts - inhibit or delay the growth of other microorganisms found in foods. Compared with the traditional Mossel medium (MYP), our medium has two distinct advantages: The non-requirement of antibiotics such as polymyxin B and reduced complexity in terms of production in the laboratory. Copyright©, International Association of Milk, Food and Environmental Sanitarians.