Evaluation of bacteriophage efficacy in reducing the impact of single and mixed infections with Escherichia coli and infectious bronchitis in chickens

Infectious bronchitis virus (IBV) represents a major threat to poultry production worldwide particularly when complicated with bacterial infection. In the present study samples were collected from forty broiler farms with respiratory manifestations to characterize IBV and E. coli. Bacteriophages were isolated and enriched from sampled farms to study its efficacy to control single and mixed infections with E. coli and IBV in vivo. Twelve out of forty farms were positive for IBV. Phylogenetic analysis of partial spike protein revealed that all positive cases clustered within the GI-23 genotype. Eight out of forty farms were positive for E. coli serogroups O26, O78, O86, O114, O119, with O125 found on three farms. Bacteriophage treatment delayed the onset and reduced the severity of clinical signs, and prevented the mortality associated with single and mixed infection with IBV and E. coli. Furthermore, in mixed infections, bacteriophage treatment significantly reduced E. coli as well as IBV shedding. Groups treated with bacteriophages showed a significant reduction of E. coli shedding that gradually decreased over time, in contrast to higher and gradually increasing shedding without bacteriophage treatment. In conclusion, bacteriophage treatment significantly reduced the pathogenicity and shedding of IBVand E. coli in mixed infections.