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.
Highlights
If management practices fail to prevent disease in commercially reared poultry, birds are routinely treated with antibiotics such as fluoroquinolones, colistin, or sulfamethoxazole/trimethoprim [1].Pathogens 2020, 9, 293; doi:10.3390/pathogens9040293 www.mdpi.com/journal/pathogensAs they have an antimicrobial effect on all susceptible microbes of the natural gut microbiota, they pose increased selective pressure, favoring the growth and spread of resistant bacteria [2]
(referred to as the four-phage trail). The results of these first trials on the reduction of E. coli in a chicken model can improve the understanding of the effect of phages on single strains in the multi-strain microbiota of the chicken gut. Both trials were conducted to examine the prophylactic effect of phage application on the colonization of the model E. coli strain E28 in broiler chickens
Inoculation doses of the model E. coli strain E28 differed between the trials and a higher concentration of phages was supplemented in the four-phage trial to achieve a high multiplicity of infection (MOI)
Summary
As they have an antimicrobial effect on all susceptible microbes of the natural gut microbiota, they pose increased selective pressure, favoring the growth and spread of resistant bacteria [2]. E. coli is an opportunistic pathogen that can cause severe disease in humans and animals, including chickens [6]. Extraintestinal pathogens such as avian pathogenic E. coli (APEC) colonize the chicken gut without causing symptoms. Prevention of intestinal colonization might, prevent infection and clinical signs of the disease. 10–15% of intestinal coliform microbes in the broiler gut are potentially pathogenic types that can cause symptoms of avian colibacillosis [7]. The occurrence of a limited number of widespread pathogenic E. coli clones [10] implies the possibility to use a specific phage cocktail for control purposes against these pathogenic E. coli [11,12,13,14]
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