A novel diagnostic real-time PCR assay for quantification and differentiation of emetic and non-emetic Bacillus cereus

To improve differential diagnosis of Bacillus cereus group and minimize a risk of bacilli related disease, a multiplex quantitative real-time PCR assay for a one step detection and differentiation of B. cereus sensu lato and emetic B. cereus spores in milk was developed.A qPCR assay with primers and probe targeting gyrB (gyrase B) gene was successfully established and applied in a multiplex qPCR approach with previously published 16S rRNA and ces (specific part of the cereulide) qPCR assays. An internal amplification control (IAC) was included to meet diagnostic PCR requirements. The inclusivity and exclusivity of the assay were assessed using a panel of 81 strains, including 45 B. cereus group, 19 non-B. cereus group and 17 non-Bacillus strains.The limit of detection (LOD) for B. cereus in artificial inoculation experiments was 1.91 × 103 spores ml−1 milk with a mean recovery rate of 81%. Good coefficient of determination was achieved between the number of B. cereus spores added and the qPCR derived number of B. cereus cell equivalents (R2 = 0.973).The real-time qPCR assay is specific and sensitive, providing an efficient diagnostic and monitoring tool for the implementation in food and clinical diagnostic labs.

► A novel qPCR assay has been developed for quantification and differentiation of emetic and non-emetic Bacillus cereus. ► We designed primers and probe specific for the gyrB gene. ► Designed gyrB qPCR was successfully applied in a multiplex qPCR approach with previously published 16S rRNA and ces qPCR assays. ► The limit of detection for B. cereus in artificial inoculation experiments was 1.91 × 103 spores ml−1 milk. ► The qPCR assay will improve diagnosis of B. cereus group and minimize a risk of bacilli related disease.