Ex-Vivo Adhesion of Enterococcus faecalis and Enterococcus faecium to the Intestinal Mucosa of Healthy Beagles

Simple SummaryBacterial adhesion to the intestinal mucosa appears to be an important feature for probiotics. When selecting bacteria for probiotic use, those with high ability to attach to the intestines are preferred. Specific strains of Enterococcus faecalis and Enterococcus faecium have been used as probiotics or feed additives. Due to the lack of information in dogs, we aimed (1) to investigate the intra- and inter-host species adhesion of E. faecalis and E. faecium to the duodenal mucosa of six healthy beagles using bacteria derived from dogs and chickens, and (2) to validate a method of quantifying the adhesion of Alexa Fluor stain-labeled bacteria to paraffin-embedded canine duodenal mucosa. Our results show that both canine- and chicken-derived E. faecalis strains adhered better than E. faecium to the duodenal mucosa of beagles. In addition, canine E. faecalis and E. faecium adhere in higher numbers to canine duodenal mucosa, compared to chicken-derived strains of the same species. Our results suggest that both the bacterial strain and the host species may influence the mucosal adhesion properties of E. faecalis and E. faecium.Some Enterococcus faecalis and E. faecium strains are used as probiotics or feed additives. Adherence to the intestinal mucosa is considered a crucial step for intestinal bacteria to colonize and further interact with the host epithelium and the immune system. In dogs, there are no studies investigating the adhesion of E. faecalis and E. faecium to paraffin-embedded intestinal mucosa. Therefore, we aimed to investigate the adhesion of E. faecalis and E. faecium to the intestinal mucosa of six healthy beagles using bacteria derived from dogs and chickens. In addition, we aimed to validate a method to test the adhesion of Alexa Fluor-labeled bacteria to paraffin-embedded canine intestinal mucosa. The results of our study show that both canine- and chicken-derived E. faecalis strains adhered significantly better than E. faecium to the duodenal mucosa of healthy beagles (p = 0.002). In addition, canine E. faecalis and E. faecium adhered in higher numbers to canine duodenal mucosa, compared to chicken-derived strains of the same species (p = 0.015 for E. faecalis and p = 0.002 for E. faecium). The determination of the hydrophobicity of bacteria revealed that canine E. faecalis had the highest hydrophobicity level (36.6%), followed by chicken E. faecalis (20.4%), while canine E. faecium (5.7%) and chicken E. faecium (4.5%) had the lowest levels. Our results suggest that both the bacterial species and the host origin of the strain may influence mucosal adhesion.