Effect of Fructooligosaccharide Metabolism on Chicken Colonization by an Extra-Intestinal Pathogenic Escherichia coli Strain

Extra-intestinal pathogenic Escherichia coli (ExPEC) strains cause many diseases in humans and animals. While remaining asymptomatic, they can colonize the intestine for subsequent extra-intestinal infection and dissemination in the environment. We have previously identified the fos locus, a gene cluster within a pathogenicity island of the avian ExPEC strain BEN2908, involved in the metabolism of short-chain fructooligosaccharides (scFOS). It is assumed that these sugars are metabolized by the probiotic bacteria of the microbiota present in the intestine, leading to a decrease in the pathogenic bacterial population. However, we have previously shown that scFOS metabolism helps BEN2908 to colonize the intestine, its reservoir. As the fos locus is located on a pathogenicity island, one aim of this study was to investigate a possible role of this locus in the virulence of the strain for chicken. We thus analysed fos gene expression in extracts of target organs of avian colibacillosis and performed a virulence assay in chickens. Moreover, in order to understand the involvement of the fos locus in intestinal colonization, we monitored the expression of fos genes and their implication in the growth ability of the strain in intestinal extracts of chicken. We also performed intestinal colonization assays in axenic and Specific Pathogen-Free (SPF) chickens. We demonstrated that the fos locus is not involved in the virulence of BEN2908 for chickens and is strongly involved in axenic chicken cecal colonization both in vitro and in vivo. However, even if the presence of a microbiota does not inhibit the growth advantage of BEN2908 in ceca in vitro, overall, growth of the strain is not favoured in the ceca of SPF chickens. These findings indicate that scFOS metabolism by an ExPEC strain can contribute to its fitness in ceca but this benefit is fully dependent on the bacteria present in the microbiota

Unveiling the participation of avian kinin ornithokinin (OK) and its receptors in the chicken inflammatory response

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Broiler lines divergently selected for digestive efficiency also differ in their susceptibility to colibacillosis

International audienceIncreasing feed efficiency of broiler chickens by selective breeding could lead to decreased feed cost and reduced environmental impact of poultry production. At INRA, two broiler chicken lines (D+/D-) were divergently selected for their digestive efficiency. Strong differences were shown between both lines for the anatomy and histology of the digestive tract, and for the intestinal microbiota composition. In the present study, we investigated whether this selection also had an effect on susceptibility to colibacillosis, which is one of the main causes of economic losses in poultry production. The broiler lines D+/D- were challenged with an avian pathogenic Escherichia coli strain. A first experiment was conducted to assess the 50% lethal dose by subcutaneous infection of hatchlings, whereas a second experiment reproduced colibacillosis by infecting air sacs of 23-day-old chicks. The 50% lethal dose was very low for both lines. However, the line with the higher digestive efficiency (D+) was the less susceptible to colibacillosis. This result is interesting for selection purposes and opens the way to integrative genetic studies of the interactions between digestion efficiency and resistance to colibacillosis

Competition between <i>E. coli</i> strains BEN2908 and BEN2908Δ<i>fosT</i> to grow in the presence of extracts of chicken intestine.

<p>Growth curves (log₁₀ CFU/ml) of strains BEN2908 (pink circle) and BEN2908Δ<i>fosT</i> (blue triangle) grown without shaking at 37°C in M9 minimal medium supplemented with (A) intestinal mucus from the ileum at 2 mg/ml of proteins, (B) intestinal mucus from the colon at 2 mg/ml of proteins, (C) 2% of cecal content from axenic chicken, (D) 2% of cecal content from SPF chicken, (E) 4% of cecal content from axenic chicken supplemented with cecal bacteria from SPF chicken. The average values and standard deviations result from three independent experiments. Asterisks indicate significant differences in mean number of CFU between BEN2908 and BEN2908Δ<i>fosT</i> determined by a Student's <i>t</i>-test. *** <i>P</i><0.005; ** <i>P</i><0.02; * <i>P</i><0.05.</p

Comparing resistance to colibacillosis of six chicken lines

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Bacterial strains and plasmids used in this study.

<p>Bacterial strains and plasmids used in this study.</p

Competition between <i>E. coli</i> strains BEN2908 and BEN2908Δ<i>fosT</i> for growth in the presence of liver extract.

<p>Growth curves (log₁₀ CFU/ml) of strains BEN2908 (pink circle) and BEN2908Δ<i>fosT</i> (blue triangle) grown without shaking at 37°C in M9 minimal medium supplemented with 4% of liver extract. The average values and standard deviations result from three independent experiments.</p

Growth of <i>E. coli</i> strains BEN2908, BEN2908Δ<i>fosT</i> and BEN2908Δ<i>fosT</i>/pGEM::<i>fos</i> in the presence of scFOS.

<p>Growth curves (OD_{450 nm}) of strains BEN2908 (pink circle), BEN2908Δ<i>fosT</i> (blue triangle) and BEN2908Δ<i>fosT</i>/pGEM::<i>fos</i> (green square) grown with shaking at 37°C in M9 minimal medium supplemented with 0.2% scFOS. The average values and standard deviations result from three independent experiments.</p

<i>fos</i> operon promoter activity in extracts of chicken intestine.

<p>Growth curves (OD_{450 nm}) and relative luminescence intensities (RLU/OD_{450 nm}) of strains BEN2908, BEN2908Δ<i>fosR</i> and BEN2908Δ<i>fosT</i> carrying pQF52 grown without shaking at 37°C in M9 minimal medium supplemented with (A) intestinal mucus from the ileum at 2 mg/ml of proteins, (B) intestinal mucus from the colon at 2 mg/ml of proteins, (C) 2% of cecal content. The RLU average values and standard deviations result from three independent experiments. Asterisks indicate significant differences in mean luciferase activity between BEN2908 and BEN2908Δ<i>fosT</i> determined by a Student's <i>t</i>-test. *** <i>P</i><0.005; ** <i>P</i><0.02; * <i>P</i><0.05.</p

Complete genome sequences of two Escherichia coli phages vB_EcoM_ ESCO5 and vB_EcoM_ESCO13 which are related to phAPEC8

International audienceWe report here the complete genome sequences of two Myoviridae phages that infect various avian-pathogenic Escherichia coli strains and that are closely related to phage phAPEC8