*Efficiency of Treatment Targeted on Gut Microbiota in Inflammatory Bowel Diseases… DOI: http://dx.doi.org/10.5772/intechopen.108664*

Górski et al. found that the phages can traverse the mucosa and enter the systemic circulation, a phenomenon discovered even in healthy subject and associated with immunomodulation [134]. Inflammation increases the intestinal permeability, and a higher number of phages enter in the circulation.

In an IBD patient, it was considered important to be able to introduce a "phage cocktail" into the colon that is not able to incorporate its genetic information into bacteria. Therefore, phages may be engineered to lack the enzyme determining the genome integration [135]. On the other hand, it may be more useful to control the switch between lytic/lysogenic life cycles, as it might be more beneficial if the phage stayed incorporated in the gut bacterial genome able to act in case of a dysbiotic state [132].

## *2.9.1 Fecal microbiota transplantation as a tool for phage therapy*

One of the first studies focusing on the composition of the virome after FMT found the transfer of viral sequences from a healthy donor to pediatric UC patients. Among the sequences, the members of Siphoviridae were transferred with greater efficiency than other groups [136]. Of particular importance is also a study by Broecker et al., who found the phage population of a recipient CDI patient after FMT to be very similar to the donor in contrast to the composition of bacteria [137].

The study of Ott and colleagues [138] demonstrated that the administration of sterile donor fecal matter to patients with Clostridium difficile infection, showing the cessation of symptoms. It is suggested that the effect of FMT can be at least partially

#### **Figure 5.**

*Schematic overview regarding the status of current standard therapy and microbial-targeted therapies as well as future treatment approaches in IBD. Legend: Tx—therapy; 5-ASA—5-aminosalicylic acid; MTX methotrexate; JAK—Janus kinase; IL—interleukin; TNF—tumor necrosis factor; SCFA—short chain fatty acid; PXR—pregnane X receptor; PPAR—peroxisome proliferator activated receptor; Treg—regulatory T cell; GOS galacto-oligosaccharide; FOS—fructo-oligosaccharide; GBF—germinated barley foodstuff; OI—oligofructoseenriched inulin; BGS—bifidogenic growth stimulator; FODMAP—fermentable oligosaccharide; disaccharide, monosaccharide and polyol; FMT—fecal microbiota transplant; LBP—live biotherapeutic product; PolyP polyphosphate; KFXL—Kangfuxin liquid; path—pathogenic; AIEC—adherent-invasive E. coli.*

determined by different parts of the bacterial cell and even non-viable bacterial vectors and phages action.
