Development of an in vitro model for the assay of plant compounds anti-bacterial activity and the monitoring of their specificity on the pig feces microbiota

The objective of our study was to develop a new in vitro model for the assay of plant compounds and the monitoring of their effects on the evolution of the pig gut microbiota. First, we determined the in vitro antibacterial activity of selected plant compounds on selected bacterial species and strains using classical methods, agar disk-diffusion and broth dilution assays; second, we developed a pig feces-containing in vitro model for the monitoring of bactericidal activity changes of selected plant compounds ( carvacrol, cinnamaldehyde, eugenol and white camphor oil); third, we analyzed the effects of selected plant compounds at different concentrations on the evolution of the pig feces bacterial microbiota diversity using high throughput sequencing (Miseq).Comparisons of alpha-diversity indices showed that increased essential oil concentrations led to an increase in richness and evenness. Pair-wise comparisons of the pig feces bacterial microbiota showed significant modifications of beta-diversities according to increased essential oil or colistin concentrations. Samples treated with high concentrations of essential oils or colistin showed similar beta-diversities. The Linear discriminant analysis effect size was performed to identify and compare OTU relative abundances and reveal differences between different groups.Our in vitro model presented in this manuscript could be used to assay a much wider variety of plant compounds and other extracts, and to monitor their effects on pig feces bacterial microbiota. It could lead to a better selection of tailor-made feed additives for the modulation of swine intestinal microbiota for specific purposes.