title: Detection and quantification of Bacillus cereus group in milk by droplet digital PCR.
abstract: Droplet digital PCR (ddPCR) is one of the newest and most promising methods for the detection and quantification of molecular targets by PCR. Here, we optimized and used a new ddPCR assay for the detection and quantification of the Bacillus cereus group in milk. We also compared the ddPCR to a standard qPCR assay. The new ddPCR assay showed a similar coefficient of determination and a better limit of detection compared to the qPCR assay during quantification of the target molecules in the samples. However, the ddPCR assay has a limitation during quantification of a high number of target molecules. This new assay was then tested for the quantification of the B. cereus group in 90 milk samples obtained over three months from two different dairies and the milk was stored at different temperatures before sampling. The ddPCR assay showed good agreement with the qPCR assay for the quantification of the B. cereus group in milk, and due to its lower detection limit more samples were detected as positive. The new ddPCR assay is a promising method for the quantification of target bacteria in low concentration in milk.
authors.affiliation: Department of Chemistry, Biotechnology and Food Science, Norwegian University of Life Science, P.O. Box 5003, N-1432 Ås, Norway. Electronic address: davide.porcellato@nmbu.no.
authors.forename: Davide
authors.initials: D
authors.lastname: Porcellato
authors.affiliation: Department of Chemistry, Biotechnology and Food Science, Norwegian University of Life Science, P.O. Box 5003, N-1432 Ås, Norway.
authors.forename: Judith
authors.initials: J
authors.lastname: Narvhus
authors.affiliation: Department of Chemistry, Biotechnology and Food Science, Norwegian University of Life Science, P.O. Box 5003, N-1432 Ås, Norway.
authors.forename: Siv Borghild
authors.initials: SB
authors.lastname: Skeie
mesh_terms: D000818:Animals; D001409:Bacillus cereus / Q000235:genetics / Q000302:isolation & purification*; D005516:Food Microbiology / Q000379:methods; D057230:Limit of Detection; D008892:Milk / Q000382:microbiology*; D016133:Polymerase Chain Reaction / Q000379:methods*; D060888:Real-Time Polymerase Chain Reaction / Q000379:methods
keywords: Bacillus cereus group; Droplet digital PCR; Milk; Quantitative PCR