Abstract:

A real-time PCR method was developed to identify Bifidobacterium in foods. Specific primers and probes targeting
the conserved region of the 16S rRNA gene of Bifidobacterium were designed. The specificity, sensitivity, reproducibility and
system anti-interference ability of the proposed method were verified. Twenty-five commercial products labeled “containing
Bifidobacterium” were tested by the real-time fluorescence PCR assay. Results showed that the developed method was
highly specific for Bifidobacterium detection. The detection limits were 2 pg using eight species of Bifidobacterium as the
templates, and the relative detection limits were 104 CFU/mL. Standard deviations and relative standard deviations (RSDs)
of Ct values for five DNA concentrations were all in the acceptable range. The Ct values were not affected by a mixture of
Bifidobacterium adolescentis ATCC15703 and Escherichia coli ATCC25922 at both the culture level and genomic DNA
level, which showed that the fluorescence PCR method has good anti-interference ability. Five samples were detected
without Bifidobacterium. Thus, considering its high specificity, sensitivity and repeatability, the real-time PCR could be used
to rapidly and accurately identify Bifidobacterium in foods.

Key words: real-time polymerase chain reaction (RT-PCR), Bifidobacterium, 16S ribosomal RNA, identification