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

Abstract

Among intestinal coliform microbes in the broiler gut, there are potentially pathogenic Escherichia (E.) coli that can cause avian colibacillosis. The treatment with antibiotics favors the selection of multidrug-resistant bacteria and an alternative to this treatment is urgently required. A chicken model of intestinal colonization with an apathogenic model strain of E. coli was used to test if oral phage application can prevent or reduce the gut colonization of extraintestinal pathogenic E. coli variants in two individual experiments. The E. coli strain E28 was used as a model strain, which could be differentiated from other E. coli strains colonizing the broiler gut, and was susceptible to all cocktail phages applied. In the first trial, a mixture of six phages was continuously applied via drinking water. No reduction of the model E. coli strain E28 occurred, but phage replication could be demonstrated. In the second trial, the applied mixture was limited to the four phages, which showed highest efficacy in vitro. E. coli colonization was reduced in this trial, but again, no reduction of the E. coli strain E28 was observed. The results of the trials presented here can improve the understanding of the effect of phages on single strains in the multi-strain microbiota of the chicken gut.

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

“…Only at MOI 0.00001 the four-phage preparation was slightly more effective than the six-phage preparation. In a subsequent in vivo study, one animal experiment was conducted with each of the two cocktails [ 21 ], confirming these findings.…”

“…To evaluate the stability of phages during administration via drinking water, we analyzed the stability at room temperature for 24 h. Only slightly reduced titers could be observed ( Figure S3B ). The actual stability of phages diluted in tap water is presented in [ 21 ]. Furthermore, the phages EW2, TriM, AB27, TB49, and KRA2 were stable for at least six weeks at 6 °C in PBS or LB medium and therefore considered suitable for long-time storage without additives.…”

“…To test the efficacy of the prevention or reduction of intestinal colonization of extraintestinal pathogenic E. coli variants we used a chicken model of intestinal colonization with an apathogenic traceable model strain of E. coli where phages were applied in a continuous manner via the drinking water as presented by Kittler et al [ 21 ]. In this follow up study the impact of the four-phage and six-phage cocktail in vivo is described.…”

“…E. coli E28 was identified as a suitable model bacterium. Traceability could be ensured by a combination of different markers and the strain colonized the gut of chickens asymptomatically [ 21 ]. Six phages were identified that proved to be the most effective against E28.…”

“…This E. coli model strain E28 allows selective quantification and differentiation from other E. coli strains as a prerequisite for the evaluation of phage efficiency in a multi-strain environment in animal trials that were conducted in a separate study subsequent to our experiments. In this case, the phages were administered preventively via the drinking water [ 21 ].…”