Properties of Bacillus cereus Collected from Different Food Sources

Abstract

Forty-nine Bacillus cereus isolates were obtained from 10 different food samples consumed in Turkey. The isolates were identified as B. cereus based on colonial, cellular morphology, and biochemical characters, including fatty acid methyl ester (FAME) analysis. The potentials of 53 isolates including a reference strain, B. cereus NRRL B-3711, and 3 strains from Japan were tested to produce diarrhoeal enterotoxin (by the BCET-RPLA test) in BHI culture and 35 isolates (66%) were positive. Fatty acid composition varied for all B. cereus isolates, with 74 different fatty acids being detected. Grouping of B. cereus isolates by fatty acid composition suggested the existence of 4 groups: A, B, C, and D. The major difference between the groups was found in the following FAME: 15:0 ISO. Automated riboprinting was applied to the 53 isolates of B. cereus to assess the genetic similarity of the isolates obtained from different food sources. The automatic ribotyping of the total genomic DNA with EcoRI yielded a total of 8 band patterns among the isolates. Grouping of the 53 randomly selected B. cereus isolates based on their genotypic and phenotypic characteristics showed that these characteristics were independent of the food source of the various strains. The use of this polyphasic approach to strain differentiation enabled all the B. cereus isolates to be distinguished from each other. However, there was no relation between the groups and food of origin.