1. Comparison of tuf gene-based qPCR assay and selective plate count for Bifidobacterium animalis subsp. lactis BB-12 quantification in commercial probiotic yoghurts.
- Author
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Odooli, S., Khalvati, B., Safari, A., Mehraban, M. H., Kargar, M., and Ghasemi, Y.
- Subjects
POLYMERASE chain reaction ,BIFIDOBACTERIUM ,PROBIOTICS ,YOGURT ,PATHOGENIC bacteria - Abstract
Yoghurt is one of the most prevalent vehicles for the delivering of probiotic bacteria to the consumer. A minimal concentration of 106 colony forming units (CFU)/ml of a product is required for optimal probiotic functionality. In this study, a new quantitative real-time PCR (qPCR) assay based on Bifidobacterial single-copy tuf gene was developed for the detection and quantification of Bifidobacterium animalis subsp. lactis BB-12. The specificity of designed primer set was evaluated by operation PCR reactionswith DNAs from common probiotic Bifidobacteria and Lactobacilli strains presented in probiotic yoghurts. Finally,BB-12 was detected and enumerated through tuf gene-based PCR, tuf gene-based qPCR and selective plate count during shelf life and after the expiry date of commercial probiotic yoghurts. Statistical comparison of enumeration by selective plate count and qPCR methods was also investigated. The PCR assay confirmed the specificity of tuf gene-based primer set for BB-12. The obtained standard curve of tuf gene-based qPCR reactions from 104-109CFU/ml was linear (R2=0.98) with the efficiency of 90.4%. Significant differences were observed among BB-12 counts measured in yoghurts with the qPCR and selective plate count. Total bacterial count averages were higher with the qPCR method compared to selective plate count. Although the counts of B.animalis subsp.lactis BB-12 had a significant decrease during shelf-life, but these counts didn't fall below CODEX standard106CFU/ml) until the expiry date of the products. In conclusion, despite the fact that the new qPCR assay developed here is a specific, rapid and easy method for quantification of both cultivable and dormant BB-12 cells, but it does not distinguish dead and viable cells. Moreover, selective plate count method doesn't detect dormant bacterial populations. We deducethat the choice of enumeration method for probiotic bacteria may have a significant effect on the results of the analysis. [ABSTRACT FROM AUTHOR]
- Published
- 2018