Application of bacteriophages to control colibacillosis in chickens
Creators: name: Hannan, Abdul
Publisher: name: Purdue University Graduate School
Year: 2022
Subjects: Animal protection (incl. pests and pathogens)

description: Antimicrobial resistant bacteria pose a serious threat to global public health. With the development of antibioticresistance far outpacing the discovery of new antibiotics, there is a need to develop alternative strategies to control bacterial infections without increasing antibiotic resistance. This study focused on developing bacteriophage therapy as a non-antibiotic means to control colibacillosis in poultry. Avian colibacillosis causes significant mortality and economic loss to poultry industries around the world. The etiological agent is Avian Pathogenic<em> E. coli</em> (APEC), with serotypes are O78, O1, O2 and O5 most often associated with infections. Here, seven bacteriophages (AHP, MP1, MP2, AKA, MKA, AHC and MIA) were isolated from human and poultry wastewater samples to target these four APEC serotypes. The host-spectrum analysis of these phages revealed that all seven phages lysed at least two different APEC strains, with four phages lysing four or more distinct APEC serotypes. Taken together, the isolated phages covered 90% (9/10) of O-serotyped APEC strains targeted in our study. When co-cultured with the targeted APEC strain, bacterial concentrations in phage treated APEC cultures (average OD<sub>600</sub>= 0.09) were significantly (P &lt; 0.05) lower than those of untreated cultures (average OD<sub>600</sub>= 1.22) after 4 hr incubation. However, exposure of the phages to simulated gastric fluid (pH 2.2–2.5) reduced viability of three of the seven phages by 2.35 –4.01 log PFU/mL after 90 min and to undetectable levels after 5 min for other four phages. In contrast, phage viability was not impacted by simulated intestinal fluid (SIF) with no reductions in phage concentrations after exposure to SIF for 3 hr. All seven bacteriophages were encapsulated in sodium alginate microcapsules with encapsulation efficiencies between 94.4% to 98.9%. In contrast to unprotected phages, viability of encapsulated phages was reduced by only0.74 –1.21 log PFU/mL when exposed to SGF for 90 min. Incubating the encapsulated phages sequentially in SGF (1 hr) and SIF (3 hr) indicated that 85% -90% of phages were released from the microcapsules after1 hr incubation in SIF with the maximum release of phages from the microcapsules occurring after 3 hr of incubation in SIF. To assess the in vivoefficacy of the phage treatment, broiler chicks were challenged with APEC and treated with a mixture of unprotected and encapsulated phages. Concentrations of the APEC in the ceca of phage treated birds (2.79 log CFU/g) were significantly lower (P &lt; 0.05) than those of untreated birds (6.18 log CFU/g) by 4 d post-challenge. Additionally, in most cases, APEC was not recovered from the lungs of phage treated birds whereas concentrations of APEC in lungs of untreated birds was 4.81 log CFU/g. Hence, these results indicate that phage treatmenteffectively controlled APEC colonization and replication in the ceca and lungs of APEC-challenged chickens and provide further evidence of the viability of phage-based treatments as a non-antibiotic means of controlling bacterial infections in chickens.