Evaluation of the ability to detect Bacillus cereus in food of chromogenic agar media RAPID’B.cereus according to ISO 7932:2004

Abstract

In this study, the ability to detect Bacillus cereus of the new chromogenic agar media RAPID’B.cereus (RBC) was compared with the standard selective culture media Mannitol Egg Yolk Polymyxin (MYP) recommended by food authorities for isolation, identification, and quantification of Bacillus cereus. Two types of media were used to conduct the assessment on five categories of food, including cereals and cereal products; flour and starch; vegetables and vegetable products; milk and dairy products; and confectionery (n = 164). The results of the survey Bacillus cereus contamination on RBC (75.61%), MYP (70.12%), of which 46.09% of the samples didn’t meet the standards of the Ministry of Health on the maximum allowable limit of Bacillus cereus in food. Conducting performance testing of RBC according to ISO 16140-2:2016 with parameters: growth, selectivity, specificity, relative trueness and accuracy profile, the analysis results all met the criteria according to the standard: the development (PR) of the two media were 0.97 and 0.81 respectively; a high level of background microflora was present on the MYP plates while if it was not the case on the RBC plates; both media allowed the detection of Bacillus cereus with a difference of 0.14.  Compared with the acceptance criteria as prescribed, the categories used in the study were all suitable for assessment in the new media with the accuracy between the two methods being equivalent.