Today people focus on healthy lifestyle. It is well known that probiotics have a number of beneficial health effects in humans. They play an important role in protecting the host against harmful microorganisms, reduce metabolic disorders and support immune functions. In the present study, we investigated 26 probiotic products: 16 commercially available ones and 10 from a local manufacturer. None of the commercial products contained all labelled LAB and some of them contained unacceptable microorganisms. Of 890 isolated strains only 420 met the criteria for LAB. Ninetyseven strains were investigated by phenotypic and genotypic methods. 16S-23S rDNA amplification was performed for all putative LAB isolates. Fifty-seven rod-shaped bacteria referred to genus Lactobacillus and 16 coccus bacteria, to genus Weissela. Two-step multiplex PCR identified the rodshaped strains to belong to four species: Lactobacillus delbrueckii ssp. bulgaricus (three strains), Lactobacillus acidophilus (four strains), Lactobacillus casei (three strains), Lactobacillus rhamnosus (two strains), Lactobacillus reuteri (four strains) and Lactobacillus plantarum (one strain). The transit tolerance of the isolated bacteria to in vitro simulated gastric juice (pH 2) was examined. Only four strains survived after 90 min of incubation. The antimicrobial activity of the native supernatants of the isolates was tested and 10 of them showed slight activity against three pathogenic bacteria. Our results demonstrated that only freshly produced products possessed the expected number of viable cells. The data revealed that one of the most common problems is the lower concentration of viable cells, misidentification and the presence of undesired microflora.

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