Sterile faecal filtrate transplantation alters phage-microbe dynamics in individuals with metabolic syndrome

Bacteriophages (phages) are bacterial viruses thathave been shown to shape microbial communities. Previous studies have shown that faecal virome transplantation can decrease weight gain and normalize blood glucose tolerance in diet-induced obese mice. Therefore,we performed a double-blind, randomised, placebo-controlled pilot study in which individuals with MetSyn were randomised to receive a faecal filtrate transplantation (FFT) from a lean healthy donor or a placebo. From baseline up to days, we assessed safety, effects on glucose metabolism, and longitudinal changes within the bacteriome and phageome. The FFT was well-tolerated and safe, and glucose variability (time between 3.9-10 mmol/L glucose) improved in the week following the FFT.The phage virion composition was significantly altered two days after FFT as compared to placebo, which coincided with more virulent phage-microbe interactions. In conclusion, we provide evidencethat gut phages can be safely administered to transiently alter the gut microbiota of recipients.