P88 Enhancing host-microbiota synergy: fruit by-product polyphenols as prebiotic adjuvants to prevent pathogenic Escherichia coli colonization
Bryan Moreno-Chamba, Julio Salazar-Bermeo, María Concepción Martínez-Madrid, Domingo Saura, Manuel Valero, Victoria Lizama, Nuria MartíAbstract
Background
Antimicrobial resistance (AMR) is an increasing global health concern, driven in part by the reduced effectiveness of antibiotics against gut pathogens. Escherichia coli remains a common cause of gastrointestinal infections, and its treatment often involves antibiotics that can also disrupt beneficial gut microbiota. This highlights the need for alternative strategies that do not rely on killing bacteria directly, an approach that can promote resistance, but instead support beneficial microbes in outcompeting pathogens. Fruit by-products, which are rich in anthocyanins and other phenolic compounds, offer a sustainable source of bioactive molecules. These compounds may help shape the gut environment by supporting protective microbial communities that limit pathogen attachment to the intestinal lining.
Objectives
This study explored the potential of phenolic extracts from grape (GRE), cherry (CHE), and strawberry (SWE) by-products to act as prebiotic agents. Specifically, we assessed whether these extracts could promote beneficial bacteria while reducing the ability of pathogenic E. coli to colonize.
Methods
Non-inhibitory concentrations of extracts were determined by a microdilution assay and were used for the experiments. The effect of the extracts was evaluated on fitness of Bifidobacterium longum by measuring biofilm formation by crystal violet staining. A Prebiotic Activity Score (PAS) was also calculated to assess selectivity in favour of beneficial B. bifidum, over E. coli, through a growth curve assay. The short-chain fatty acids production by extract-treated B. longum were determined by HPLC-DAD. Finally, a competitive adhesion assay using Caco-2 intestinal epithelial cells was performed to model how these extracts influence bacterial attachment in a host-like environment.
Results
After confirming the inhibitory concentration of extracts against B. longum and E. coli, the extracts managed to promote the initial biofilm formation of B. longum. SWE promoted the preformed biofilm of B. longum while CHE improved mature biofilm of B. longum (P<0.05). After a growth curve assay, all samples showed positive PAS but with no statistical differences (P>0.05), displaying a selective effect promoting the growth of B. longum instead of E. coli. This was translated in a high lactate, acetate and butyrate production by B. longum after incubation (P<0.05). Ultimately, the PAS results were reflected in a competitiveness assay, where the samples showed a noted effect reducing the adhesion of E. coli, especially during competition with B. longum (P<0.05), improving the effect of the beneficial strain.
Conclusions
Anthocyanin-rich extracts from grape, cherry, and strawberry by-products demonstrate significant potential as functional ingredients for gut health maintenance. These extracts promote the growth, adhesion, and biofilm formation of Bifidobacterium longum, while maintaining selective activity against pathogenic Escherichia coli, as indicated by positive PAS. In competitive adhesion assays utilizing Caco-2 intestinal epithelial cell models, the presence of these extracts enhances the competitive ability of B. longum, effectively reducing E. coli attachment. These data confirm the capacity of the extracts to modulate both microbiota composition and host–microbe interactions, supporting their utility as nutraceutical agents to strengthen the intestinal barrier and limit pathogenic colonization.