In vivo assessment of bacteriophages specific to multidrug resistant Escherichia coli on fecal bacterial counts and microbiome in nursery pigs.

Escherichia coli is the most common cause of economic loss in swine industry. Nowadays, bacteriophages have been proven as good candidates for controlling bacterial infections. In this study, 6 phages were isolated and selected based on their high efficacy against 11 stains of E. coli isolated from diarrheal pigs. Six groups of weaned piglets were assigned (control, bacterial control (BC), two phage control (PC) and two phage treatment (PT) groups). Two titers (2 × 10 PFU/animal and 2 × 10 PFU/animal) of phage cocktails consisting of these phages were tested in the PC and PT groups via oral gavage at 24, 48, and 72 h against an E. coli cocktail (2 × 10 CFU/animal) that was given to the piglets at 0, 12, 24, and 48 h of the trial. A significant reduction of fecal E. coli counts was observed in both PT groups from day 1 to 7 following the final phage dosage when compared to those of the BC group. Microbiomes in feces obtained 24 h after the final phage administration revealed phage therapy with both dosages could restore the gut's bacterial composition. Moreover, the given phage cocktails resulted in a significantly higher average daily gain of piglets during the first few weeks in both PC groups and the PT group receiving a higher phage dosage. These findings suggest that bacteriophages might be a potential alternative to antibiotics in the treatment of pathogens. In addition, they could also be utilized to improve pig growth performance.