The intestinal microflora (microbiome) plays a vital role in the functioning of the human body. Consequently, there is a need for tools that can subtly and delicately influence the composition of microbial communities in the gastrointestinal tract. Bacteriophages—bacterial viruses that are increasingly used to treat bacterial infections—offer a convenient tool for selectively targeting unwanted members of the intestinal microbiome. However, the question of how ingested bacteriophages affect the intestinal ecology remains open.

Scientists from Colorado State University (USA) tested* a phage cocktail containing four bacteriophages specific to Escherichia coli in a double-blind, placebo-controlled, crossover study. They were interested in how the phages would affect the composition of the human microbiota and markers of systemic and intestinal inflammation.

Forty-three trial participants aged 18 to 65 were randomly divided into two groups: one received a phage cocktail for 28 days, the other a placebo, and then, after a two-week break, they switched. During the study, blood and stool samples were collected to determine markers of inflammation, lipid metabolism, and the composition of the intestinal microflora.

The phage cocktail did not cause a global disruption of the microbiome composition. However, individual bacterial populations changed, including a significant decrease in the number of E. coli and bacteria from taxa related to Clostridium perfingens . At the same time, the number of members of the genus Eubacterium increased.

Short-chain fatty acid production, inflammatory marker levels, and lipid metabolism did not undergo significant changes following treatment, but a decrease in circulating interleukin-4 levels was observed. The authors note that the study demonstrated the potential of bacteriophages to selectively target specific members of the microbiome without globally altering the intestinal ecology.

* Hallie P. Febvre, Sangeeta Rao, Melinda Gindin et al. PHAGE Study: Effects of Supplemental Bacteriophage Intake on Inflammation and Gut Microbiota in Healthy Adults // Nutrients 2019, 11(3), 666; https://doi.org/10.3390/nu11030666