Effectiveness of a single-dose phage cocktail on the reduction of multidrug-resistant Escherichia coli in suckling piglets.

Antibiotics are commonly used in pig farming to control infections caused by diarrhea-causing Escherichia coli (E. coli). However, improper or excessive use of antibiotics in pigs can enhance antibiotic resistance (ABR). This study used bacteriophage (phage) treatment to control ABR E. coli in diarrheal suckling piglets. Fifty E. coli isolates were previously isolated from suckling pigs, which showed resistance to amoxicillin (100 %), oxytetracycline and neomycin (94 %), sulfamethoxazole-trimethoprim (70 %), gentamicin (56 %), cephalexin (54 %), enrofloxacin (42 %), and colistin (28 %). Five phages (WPEC1, WPEC2, WPEC3, WPEC4, and WPEC5) were included in this study. These phages showed a diverse lytic profile ranging from 46.0 % to 64.0 % on the tested ABR E. coli isolates. The phage cocktail reduced the count of five representative E. coli by showing up to 8 log-units reduction (p < 0.05) after phage treatment for 6-24 h. From the in vivo study, a single dose of the phage cocktail (9 log PFU/mL) reduced the number of E. coli present in the gastrointestinal tract of suckling piglets by showing a 1.33 log-units reduction on day 7 (p < 0.05). In addition, the fecal score of the phage treatment group was lower than that of the control group (p < 0.05). However, body weight gain (BWG) and average daily gain (ADG) were not significantly different in both groups (p > 0.05). These findings suggest that a developed phage cocktail could be used as a potential biocontrol to fight ABR E. coli, reduce the chance of piglet mortality, and increase safety during pig production.