Colonization of human feces-derived bacteria in the germ-free pig guts

Although mice are used as model animals in most studies of gut microbiota, intestinal environments of mice, such as the intestine size, intraluminal pH and transit time of diets, are different from those of humans. In pigs, these features are similar to those of humans. Here, to evaluate the possibility to utilize pigs as model animals in this field, we transplanted human gut microbiota into germ-free pigs and compared their gut microbiota to those of humans. After transplantation of human feces into germ-free pigs, bacteria derived from the human gut microbiota successfully colonized in the pig guts, confirmed by microbial culture of their feces. Metagenomic 16S rRNA sequencing revealed that the dominant species of bacteria in pig gut microbiota at 13 days after transplantation was Enterococcus faecium, as was the case with those of control pigs (specific pathogen-free pigs). On the other hand, E. faecium was only little detected in those of humans. E. faecium in the transplanted pigs' guts, however, decreased over-time after transplantation. Finally, the diversity and composition of pig gut microbiota three months after transplantation faithfully resembled those of humans. These results indicated that human fecal-transplanted pigs have the potential as model animals for studies of human gut microbiota.