A cocktail of several bacteriophages successfully combated a strain of E. coli pathogenic to humans without harming the gut microbiota in mice. The results of the study were published in the journal Frontiers in Microbiology*.

A total of 85 mice were infected with nalidixic acid-resistant (NalAcR) Escherichia coli O157:H7 strain Ec231 via a gavage. The mice were randomly divided into six groups in three categories. The first category received a phosphate-buffered saline or a control (no buffer/no phages). The second category received a cocktail of bacteriophages specific for E. coli/Salmonella spp./Listeria monocytogenes (abbreviated FOP), FOP at a 1:10 dilution, or only the FOP component specific for E. coli . The third category received the antibiotic ampicillin.

All treatments were administered twice daily for four days post-infection, except for ampicillin, which was also administered on day 0—before and after infection. Fecal samples were collected on days 0, 1, 2, 3, 5, and 10, and the number of live Ec231 and microbiota composition were determined.

The FOP cocktail reduced the number of pathogenic E. coli by more than 55%. A similar effect was observed with ampicillin. No changes in the composition of the intestinal microbiota were observed in the control (category one) and FOP (category two) groups. In contrast, the ampicillin group (category three) showed significant disturbances in the microbiota composition; partial normalization of the microbiota occurred only on the tenth day. Moreover, animals receiving ampicillin, unlike the other groups, lost weight during treatment.

Thus, the authors conclude that the FOP phage cocktail is no worse than ampicillin in reducing the number of pathogenic E. coli in the intestine, but, unlike the antibiotic, does not have a negative impact on the intestinal microbiota.

Read also about experiments with phage therapy for E. coli infection in Denmark: Phage cocktail tested against E. coli

* Dissanayake UA, Ukhanova M, Moye ZD, Sulakvelidze A and Mai V. Bacteriophages reduce pathogenic Escherichia coli counts in mice without distorting gut microbiota // Front. Microbiol., 2019. doi: 10.3389/fmicb.2019.01984