20.500.12556/RUL-132100 Evaluation of dietary supplements containing viable bacteria by cultivation/MALDI-TOF mass spectrometry and PCR identification The insufficient quality of products containing beneficial live bacteria in terms of content and viability of labelled microorganisms is an often-reported problem. The aim of this work was to evaluate the quality of dietary supplements containing viable bacteria available in Slovenian pharmacies using plate counting, matrix-assisted laser desorption ionisation time-of-flight mass spectrometry (MALDI-TOF MS) and species- or subspecies-specific PCR with DNA isolated from consortia of viable bacteria, from individual isolates, or directly from the products. Twelve percent of the products (3 of 26) contained insufficient numbers of viable bacteria. Eighty-three of the labelled species (111 in total) were confirmed by PCR with DNA from the product; 74% of these were confirmed by PCR with DNA from viable consortium, and 65% of these were confirmed by MALDI-TOF MS analysis of colonies. Certain species in multi-strain products were confirmed by PCR with DNA from viable consortia but not by MALDI-TOF MS, suggesting that the number of isolates examined (three per labelled strain) was too low. With the exception of Lacticaseibacillus casei and closely related species (Lacticaseibacillus rhamnosus and Lacticaseibacillus zeae), PCR and MALDI-TOF identification results agreed for 99% of the isolates examined, although several MALDI-TOF results had lower score values (1.700–1.999), indicating that the species identification was not reliable. The species L. zeae, which appeared in 20 matches of the Biotyper analysis, was identified as L. rhamnosus by PCR. The MALDI-TOF MS analysis was also unsuccessful in detecting Lactobacillus acidophilus La-5 and Bacillus coagulans due to missing peaks and unreliable identification, respectively. Mislabelling was detected by both methods for two putative L. casei strains that turned out to belong to the species Lacticaseibacillus paracasei. PCR remains more successful in subspecies-level identification as long as the database of MALDI-TOF MS spectra is not expanded by building in-house databases. The lack of positive PCR results with viable consortia or colonies, but positive PCR results with DNA isolated directly from the products observed in 10% (11/112) of the labelled strains, suggests the presence of non-culturable bacteria in the products. MALDI-TOF MS is a faster and simpler alternative to PCR identification, provided that a sufficient number of colonies are examined. Generation of in-house library may further improve the identification accuracy at the species and sub-species level. lactobacilli bifidobacteria dietary supplements MALDI-TOF MS identification probiotic PCR viability dietary supplements mikrobiologija probiotiki prehranska dopolnila true false true Angleški jezik Slovenski jezik Članek v reviji 2021-10-12 14:00:20 2021-10-12 14:00:21 2023-03-24 03:37:00 0000-00-00 00:00:00 2021 0 0 14 str. art. 700138 Vol. 12 2021 0000-00-00 Zaloznikova Objavljeno NiDoloceno 0000-00-00 0000-00-00 0000-00-00 579 1664-302X 10.3389/fmicb.2021.700138 67936003 RAZ_Mohar_Lorbeg_Petra_2021.pdf RAZ_Mohar_Lorbeg_Petra_2021.pdf 1 9642F2F9BF8A397CD079F1B44655E331 e3c9e3301eb97271b47e54fc0da47ab30a66b0a1cf84b6c7edb3617928c35d08 f3f5bd95-71da-11ec-abdb-00155dcfd717 https://repozitorij.uni-lj.si/Dokument.php?lang=slv&id=152746 https://www.frontiersin.org/articles/10.3389/fmicb.2021.700138/full 0 fbdc9ea2-2b53-11ec-abdb-00155dcfd717 https://repozitorij.uni-lj.si/Dokument.php?lang=slv&id=149622 Biotehniška fakulteta Veterinarska fakulteta 0 0 0