Toward an accessible and robust in vitro approach to evaluate bacterial viability in the upper gastro-intestinal tract: A Gastro-Intestinal Digestive Simulator (GIDS) combined with alternative methods to plating

Abstract

Since the viability throughout the human gastro-intestinal (GI) tract is a key metric to select new probiotics, we aimed to develop an evolutive and robust semi-dynamic model, named Gastro-Intestinal Digestive Simulator (GIDS), mimicking pH variations of the upper GI tract and based on the latest Infogest in vitro digestion protocol recommendations. We first tested the GIDS and its reproducibility by measuring, during in vitro digestion, the cultivability of bacterial strain contained in two marketed fermented milk products. Then, we used this model to assess inter- and intra-species variability among 16 bacterial strains from Bifidobacterium animalis, Bifidobacterium breve, and Lactobacillus paracasei species. Finally, we further explored the applicability of propidium monoazide-quantitative PCR and flow cytometry to GIDS samples. To summarize, our study showed that i) the GIDS model is reproducible and ii) the complementary methods to plating tested here are compatible with GI environments; providing insights that will guide future developments.

Keywords

• Gastro-intestinal in vitro model
• Viability
• Bacteria
• PMA-qPCR
• Flow cytometry