MiniBioReactor Array (MBRA) in vitro gut model: a reliable system to study microbiota-dependent response to antibiotic treatment.

Background: Antimicrobial drugs are mostly studied for their impact on emergence of bacterial antibiotic resistance, but their impact on the gut microbiota is also of tremendous interest. In vitro gut models are important tools to study such complex drug-microbiota interactions in humans. Methods: The MiniBioReactor Array (MBRA) in vitro microbiota system; a single-stage continuous flow culture model, hosted in an anaerobic chamber; was used to evaluate the impact of three concentrations of a third-generation cephalosporin (ceftriaxone) on faecal microbiota from two healthy donors (treatment versus control: three replicates per condition). We conducted 16S microbiome profiling and analysed microbial richness, diversity and taxonomic changes. ß-Lactamase activities were evaluated and correlated with the effects observed in the MBRA in vitro system. Results: The MBRA preserved each donor's specificities, and differences between the donors were maintained through time. Before treatment, all faecal cultures belonging to the same donor were comparable in composition, richness, and diversity. Treatment with ceftriaxone was associated with a decrease in α-diversity, and an increase in ß-diversity index, in a concentration-dependent manner. The maximum effect on diversity was observed after 72 h of treatment. Importantly, one donor had a stronger microbiota ß-lactamase activity that was associated with a reduced impact of ceftriaxone on microbiota composition. Conclusions: MBRA can reliably mimic the intestinal microbiota and its modifications under antibiotic selective pressure. The impact of the treatment was donor- and concentration-dependent. We hypothesize these results could be explained, at least in part, by the differences in ß-lactamase activity of the microbiota itself. Our results support the relevance and promise of the MBRA system to study drug-microbiota interactions.

Antigen sampling by intestinal M cells is the principal pathway initiating mucosal IgA production to commensal enteric bacteria.

Secretory IgA (SIgA) directed against gut resident bacteria enables the mammalian mucosal immune system to establish homeostasis with the commensal gut microbiota after weaning. Germinal centers (GCs) in Peyer's patches (PPs) are the principal inductive sites where naive B cells specific for bacterial antigens encounter their cognate antigens and receive T-cell help driving their differentiation into IgA-producing plasma cells. We investigated the role of antigen sampling by intestinal M cells in initiating the SIgA response to gut bacteria by developing mice in which receptor activator of nuclear factor-κB ligand (RANKL)-dependent M-cell differentiation was abrogated by conditional deletion of Tnfrsf11a in the intestinal epithelium. Mice without intestinal M cells had profound delays in PP GC maturation and emergence of lamina propria IgA plasma cells, resulting in diminished levels of fecal SIgA that persisted into adulthood. We conclude that M-cell-mediated sampling of commensal bacteria is a required initial step for the efficient induction of intestinal SIgA.

Saturnism caused by hand-made plates: partial diagnosis by a computer-aided program.

A man, aged 41 years, suffering from anaemia and abdominal pains was admitted to the Department of Medicine. Over the previous 2 years he had had several periods in hospital for these symptoms. There was, apparently, no occupational or accidental exposure to toxic substances and a correct diagnosis of the condition had not been possible. The computer-aided program AIDEDIAG II was therefore used to attempt a diagnosis. This approach indicated possible saturnism which was confirmed by metabolic and lead analyses. The lead source was identified as the hand-made food-plates used by the patient for his meals.