**6. Safety considerations for FVT**

While therapeutic application of FMT has been explored in many settings of dysbiosis [65–68], current clinical guidelines recommend that FMT should only be used as a last resort for rCDI due to the various safety concerns [69]. Much of the risk of FMT comes from the transfer of bacteria into an immuno-compromised recipient and the potential of inducing an unanticipated bacteria-driven phenotype (e.g., obesity). Accordingly, FVT may be associated with less risk due to the removal of intact bacteria prior to transplantation. However, since viruses are also capable of eliciting a pro-inflammatory response [12, 14], more research needs to be done to better understand how FVT interacts with the recipient host.

Safe clinical application of FVT will also require a deeper understanding of the viruses that comprise the gut virome. Numerous disease-causing viruses reside in the gut including herpesvirus, papillomaviruses, and hepatitis viruses. Sequencing of the virome has revealed numerous other viruses including bocaviruses, enteroviruses, rotaviruses, and sapoviruses [28]. Many of these viruses have yet to be characterized and their function in the gut is unknown. Given the potential for infection by eukaryotic viruses, a thorough screening of the donor virome must be done to ensure that no harmful eukaryotic viruses are transferred into the recipient. The metagenome of the virome should also be screened since phages can encode genes for virulence factors (e.g., diphtheria toxin, shiga toxin, and botulinum toxin) and antibiotic resistance (e.g., β-lactamases) [70, 71].

Overall, the removal of bacteria is likely to make FVT a safer option than FMT. However, FVT still has safety considerations that must be better understood and effectively taken into account.

### **7. Conclusion**

The emerging field of research focused on the gut virome is still in its infancy, in part due to the difficulty of studying viruses in the gut environment. However, similar to the field of microbiome research, recent work on the gut virome demonstrates how previously overlooked inhabitants of the gut have a profound influence on, and are in fact inseparable from, health and disease. In the setting of FMT, the emerging association between uptake of the donor's phage community and clinical outcome suggests that fecal phages may have an important but not yet fully

*Fecal Virome Transplantation DOI: http://dx.doi.org/10.5772/intechopen.95469*

characterized role in successful treatment of rCDI. Whether FVT will offer a safer or more effective alternative to FMT remains to be seen. We still have yet to determine the full therapeutic potential of FVT, but the promising preliminary findings on FVT suggest it may provide new treatment options for dysbiosis and dysbiosisassociated disorders. Collectively, these recent advances argue for more attention to be given to FVT as a therapeutic tool for microbiome modulation and to the gut virome as a therapeutic target.
