Efficacy of phage therapy in poultry: a systematic review and meta-analysis

The increasing prevalence of antimicrobial resistant bacteria has sparked a renewed interest in alternative bacterial control methods, including bacteriophage administration. In order to determine the overall efficacy of bacteriophage administration for the reduction of bacterial concentrations in poultry, a systematic literature review and a meta-analysis were conducted. The systematic review included studies in which 1) live chickens were challenged with a known quantity of bacteria; and 2) challenged chickens were administered a known quantity of bacteriophages; and 3) concentrations of the challenge bacteria were measured in tissue/fluid samples from both challenged and unchallenged chickens after phage administration; and 4) either standard deviation or standard error was reported. Results of a meta-analysis of the 12 studies included in this review (total inputs: n = 41; total observations: n = 711) indicated that concentrations of challenge bacteria were significantly lower (P < 0.001) in challenged, phage-treated chickens than in challenged, untreated chickens (effect size = −0.82 log(10) cfu/g). Phage treatment effects were significantly greater (P < 0.01) in chickens administered phages via feed than in chickens administered phages via drinking water or aerosol spray. No significant differences were observed between subgroups when data were disaggregated by various other experimental characteristics, though some significant differences were observed across subgroups after further disaggregation by sampling time and animal age. As a whole, findings from the systematic review and meta-analysis indicate that phage administration can significantly lower concentrations of targeted bacteria in chickens and that, in some instances, the effect may be greater in the short-term vs. the long-term and in older vs. younger chickens.