The widespread occurrence of drug-resistant bacteria has increased interest in alternatives to antibiotics for combatting bacterial infections, among which bacteriophages play an important role. The ability of phage proteins to induce an anti-phage immune response can significantly limit the effectiveness of treatment, which was the basis for the study described in this article. The aim of the study was to assess the effects of bacteriophages on the induction of an anti-phage humoral response in calves.

This study targeted isolation and characterization of potential bacteriophages (phages) infecting MDR pathogenic bacteria recovered from chickens and analyzed their efficacy as bio-control agents. A total of 45 different bacterial isolates (18 E. coli, 16 Salmonellae spp., 5 Staphylococcus spp., 2 Pseudomonas spp., 1 Proteus mirbalis, 1 Citrobacter spp., 1 Enterobacter aerogenes and 1 Klebsiella pneumonia) were obtained from chickens in the current study and previous studies. The identified isolates were investigated for the presence of virulence genes and MDR using PCR and disc diffusion method, respectively. Nine purified phages classified morphologically into 3 families (Myoviridae, Siphoviridae and Podoviridae) using Transmission Electron Microscope were recovered from chicken intestinal contents and showed viability at wide pH range, resistance to organic solvents and thermostability at high temperatures (up to 80ºC). The potential phages exhibited various bacterial host ranges using the spot test and the efficiency of plating (EOP) assay. The results revealed the prevalent of pathogenic E. coli and salmonella serovars among the recovered isolates with different virulence and genotypic patterns. The lytic phages were highly stable and have the capacity to infect different pathogenic MDR bacterial strains. This study demonstrated that these promising phages of avian origin could be used to control the pathogenic MDR E. coli and Salmonella serovars which possess public concerns on human health and poultry industry.