Quantitative Recovery of Viable Lactobacillus paracasei CNCM I-1572 (L. casei DG®) After Gastrointestinal Passage in Healthy Adults.

Stefania Arioli,Simone Guglielmetti,Ranjan Koirala,Valentina Taverniti,Walter Fiore

doi:10.3389/fmicb.2018.01720

Abstract

Probiotics are live microorganisms, and viability after transit through the gastrointestinal tract (GIT) is considered an inherent property of the health benefits of probiotics. The aim of the present study was to quantify the viable and total loads of Lactobacillus paracasei DG cells after passage through the GIT following the consumption of the probiotic product Enterolactis (L. casei DG®; L. paracasei CNCM I-1572; L. paracasei DG) from drinkable vials by healthy adults. We developed a novel method for discriminating and enumerating culturable L. paracasei DG cells based on the unique sticky, filamentous phenotype of this strain on MRS agar containing vancomycin and kanamycin. The identity of DG was also confirmed with strain-specific primers by colony PCR. This method was used for a recovery study of the DG strain to quantify viable cells in the fecal samples of 20 volunteers during a 1-week probiotic consumption period and a 1-week follow-up. We isolated L. paracasei DG from at least one fecal sample from all the volunteers. The highest concentration of viable DG cells [ranging from 3.6 to 6.7 log10 colony-forming unit (CFU) per gram of feces] in the feces was observed between 4 and 8 days from the beginning of Enterolactis intake and for up to 5 days after cessation of intake. As expected, the total DG count determined by real-time quantitative PCR (qPCR) was mostly higher than the viable DG cells recovered. Viable count experiments, carried out by combining ad hoc culture-based discriminative conditions and strain-specific molecular biological protocols, unambiguously demonstrated that L. paracasei DG can survive gastrointestinal transit in healthy adults when ingested as Enterolactis in drinkable vials containing no less than one billion CFU at the end of shelf life.

Highlights

Probiotics are “live microorganisms that, when administered in adequate amounts, confer a health benefit on the host” (Hill et al, 2014)
Microbial cell viability is constantly monitored for each marketed probiotic product, only limited data are available regarding the capacity of a particular microbial strain in a specific probiotic formulation to survive in the gastrointestinal tract (GIT) upon ingestion
We present the development of a strategy that combines culture-based methods and molecular methods for strain-specific selective enumeration of viable L. paracasei DG cells in fecal samples

Summary

Introduction

Probiotics are “live microorganisms that, when administered in adequate amounts, confer a health benefit on the host” (Hill et al, 2014). According to the regulations of numerous countries, the actual number of microbial colony-forming units (CFUs) in a probiotic product cannot be lower than the value indicated on REVENANT-DG: L. paracasei DG Recovery Study the label until the end of the shelf life of the product. Both producers and competent public authorities constantly assess the viable counts of commercial probiotic products to ensure compliance with label specifications. The first “FAO/WHO Expert Consultation on Evaluation of Health and Nutritional Properties of Probiotics” stated that the ability to remain viable at the target site should be verified for each potential strain (FAO/WHO, 2001)

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Results