Identification of Lactobacillus delbrueckii and Streptococcus thermophilus Strains Present in Artisanal Raw Cow Milk Cheese Using Real-time PCR and Classic Plate Count Methods


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Polish Journal of Microbiology

Polish Society of Microbiologists

Subject: Microbiology


ISSN: 1733-1331
eISSN: 2544-4646





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VOLUME 66 , ISSUE 4 (December 2017) > List of articles

Identification of Lactobacillus delbrueckii and Streptococcus thermophilus Strains Present in Artisanal Raw Cow Milk Cheese Using Real-time PCR and Classic Plate Count Methods

Milena A. Stachelska *

Keywords : Lactobacillus delbrueckii, Streptococcus thermophilus, artisanal cheese microflora, LAB identification

Citation Information : Polish Journal of Microbiology. Volume 66, Issue 4, Pages 491-499, DOI:

License : (CC BY-NC-ND 4.0)

Received Date : 28-March-2017 / Accepted: 23-May-2017 / Published Online: 04-December-2017



The aim of this paper was to detect Lactobacillus delbrueckii and Streptococcus thermophilus using real-time quantitative PCR assay in 7-day ripening cheese produced from unpasteurised milk. Real-time quantitative PCR assays were designed to identify and enumerate the chosen species of lactic acid bacteria (LAB) in ripened cheese. The results of molecular quantification and classic bacterial enumeration showed a high level of similarity proving that DNA extraction was carried out in a proper way and that genomic DNA solutions were free of PCR inhibitors. These methods revealed the presence of L. delbrueckii and S. thermophilus. The real-time PCR enabled quantification with a detection of 101–103 CFU/g of product. qPCR-standard curves were linear over seven log units down to 101 copies per reaction; efficiencies ranged from 77.9% to 93.6%. Cheese samples were analysed with plate count method and qPCR in parallel. Compared with the classic plate count method, the newly developed qPCR method provided faster and species specific identification of two dairy LAB and yielded comparable quantitative results.

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