Bifidobacterium animalis subsp.lactis i797,a probiotic strain with potential therapeutic applications in paediatric diarrhoea and dyspepsia,was subjected to a comprehensive Whole Genome Sequencing-Single Nucleotide Polymorphism(WGS-SNP)analysis among a set of 23 strains.This analysis identified a unique genomic locus on the K1717_01615 gene that is exclusive to strain i797.Utilizing this locus,we developed primers and probes for a fluorescence quantitative PCR-based quantitative analysis method.The method was capable of distinguishing strain i797 from 18 other Bifidobacterium strains,and demonstrated stability over 40 passages.Sensitivities for DNA concentrations and cell densities of strain i797 were established at 1.5 pg and 104 CFU/mL,respectively.In terms of repeatability and reproducibility,the relative standard deviations of the method were found to be below 2％and 6％,respectively.In addition,the method demonstrated strong anti-interference properties for high cell densities of the same subspecies of strain ATCC 27673.This method enables precise quantitative analysis of strain i797 in complex probiotic prod-ucts.The study presents an innovative strain-specific quantitative analysis method that can be used as a potent tool for ensuring the quality control and compliance assessment of probiotic products.
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