In Vitro Evaluation of a Phage Cocktail Controlling Infections with Escherichia coli

Abstract

Worldwide, poultry industry suffers from infections caused by avian pathogenic Escherichia coli. Therapeutic failure due to resistant bacteria is of increasing concern and poses a threat to human and animal health. This causes a high demand to find alternatives to fight bacterial infections in animal farming. Bacteriophages are being especially considered for the control of multi-drug resistant bacteria due to their high specificity and lack of serious side effects. Therefore, the study aimed on characterizing phages and composing a phage cocktail suitable for the prevention of infections with E. coli. Six phages were isolated or selected from our collections and characterized individually and in combination with regard to host range, stability, reproduction, and efficacy in vitro. The cocktail consisting of six phages was able to inhibit formation of biofilms by some E. coli strains but not by all. Phage-resistant variants arose when bacterial cells were challenged with a single phage but not when challenged by a combination of four or six phages. Resistant variants arising showed changes in carbon metabolism and/or motility. Genomic comparison of wild type and phage-resistant mutant E28.G28R3 revealed a deletion of several genes putatively involved in phage adsorption and infection.

Impact of Bacteriophage-Supplemented Drinking Water on the E. coli Population in the Chicken Gut

“…A well typed phage cocktail was composed for each experiment, as described by Korf et al [25]. Briefly, phages were isolated from manure and surface water, using E. coli isolates from animal origin, laboratory strains, and isolates from the ECOR collection.…”

“…Subsequently, the included phages were further characterized. The phages all belong to the virus family Myoviridae and represent members of the morphotypes A1 (EW2, AB27, KRA2), A2 (G28, TB49) and A3 (TriM) [25].…”

“…Including only the four phages that proved most effective in vitro and deleting the phages KRA2 and TriM resulted in the four-phage cocktail that was used in the second trial [25]. Accordingly, the cocktail for the four-phage trial was composed of the phages AB27, TB49, G28, and EW2 in equal parts.…”

“…The phages EW2, AB27, G28, TB49, KRA2, and TriM that were used in this study all belong to the virus family Myoviridae and represent members of the morphotypes A1 (EW2, AB27, KRA2), A2 (G28, TB49), and A3 (TriM) [25]. TB49 lysed 50% of the 66 host strains tested, while the host range of the other phages ranged from 12% to 29%.…”

“…The applied cocktail was selected based on its high lytic efficacy in broth culture. Including only the four phages that proved most effective in vitro and deleting the phages KRA2 and TriM resulted in the four-phage cocktail that was used in the second trial [25].…”