The Presence of Bacteriophages in the Human Body: Good, Bad or Neutral?

The presence of bacteriophages (phages) in the human body may impact bacterial microbiota and modulate immunity. The role of phages in human microbiome studies and diseases is poorly understood. However, the correlation between a greater abundance of phages in the gut in ulcerative colitis and diabetes has been suggested. Furthermore, most phages found at different sites in the human body are temperate, so their therapeutic effects and their potential beneficial effects remain unclear. Hence, far, no correlation has been observed between the presence of widespread crAssphage in the human population and human health and diseases. Here, we emphasize the beneficial effects of phage transfer in fecal microbiota transplantation (FMT) in Clostridioides difficile infection. The safety of phage use in gastrointestinal disorders has been demonstrated in clinical studies. The significance of phages in the FMT as well as in gastrointestinal disorders remains to be established. An explanation of the multifaceted role of endogenous phages for the development of phage therapy is required.