Peanut fractions boost the growth of Lactobacillus casei that alters the interactions between Campylobacter jejuni and host epithelial cells

Since gut microbiota elicit host responses that impact human health and affect the nutritional value of animal products, the modulation of gut flora with a combination of natural prebiotics and probiotics, known as synbiotic, is an area of significant research interest. In this study, we evaluated the role of peanut fractions on the growth of Lactobacillus casei and Campylobacter jejuni, a probiotic and pathogenic bacteria, respectively. Moreover, in a co-culture system, we investigated whether there are synergistic effects between the bacterium in the presence of the peanut fraction. We observed that water-soluble (5g/L) and alcalase-treated peanut fraction significantly stimulated L. casei growth by more than 1.5 logs at 24h. However, the peanut fraction had no direct effect on C. jejuni growth. Analysis of the fatty acids profile suggested that the higher percentage of oleic acid present in peanuts might be responsible for stimulation of L. casei growth. The initial pH of medium ranging from 6 to 8 did not alter the growth of C. jejuni. In a co-culture system in the presence of the water soluble peanut fraction, the growth of C. jejuni was inhibited in a time dependent manner, reaching the highest level of inhibition (~2 logs) at 72h, while no growth difference was observed in absence of peanut fractions or even in presence of alcalase-treated peanut fraction. In addition, L. casei competitively reduced the colonization of C. jejuni on human intestinal epithelial (INT407) cells. Our data suggest that peanut fraction induced the growth of L. casei, which in turn led to a reduction in the growth of C. jejuni as well as its colonization. Therefore, we hypothesize that regular consumption of peanuts may positively impact on the composition of human gut microbiota and decrease the burden of gastrointestinal infections by enteric bacterial pathogens.