AUTHOR=Chagneau Sophie , Gaucher Marie-Lou , Thériault William P. , Fravalo Philippe , Thibodeau Alexandre 

TITLE=Observations supporting hypothetical commensalism and competition between two Campylobacter jejuni strains colonizing the broiler chicken gut

JOURNAL=Frontiers in Microbiology

VOLUME=13

YEAR=2023

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2022.1071175

DOI=10.3389/fmicb.2022.1071175

ISSN=1664-302X

ABSTRACT=<p><italic>Campylobacter jejuni</italic> is the most prevalent bacterial foodborne pathogen in humans. Given the wide genetic diversity of <italic>C. jejuni</italic> strains found in poultry production, a better understanding of the relationships between these strains within chickens could lead to better control of this pathogen on farms. In this study, 14-day old broiler chickens were inoculated with two <italic>C. jejuni</italic> strains (10<sup>3</sup> or 10<sup>7</sup> CFU of D2008b and 10<sup>3</sup> CFU of G2008b, alone or together) that were previously characterized <italic>in vitro</italic> and that showed an opposite potential to compete for gut colonization in broilers. Liver samples and ileal and cecal contents were collected and used to count total <italic>C. jejuni</italic> and to quantify the presence of each strain using a strain specific qPCR or PCR approach. Ileal tissue samples were also collected to analyze the relative expression level of tight junction proteins. While a 10<sup>3</sup> CFU inoculum of D2008b alone was not sufficient to induce intestinal colonization, this strain benefited from the G2008b colonization for its establishment in the gut and its extraintestinal spread. When the inoculum of D2008b was increased to 10<sup>7</sup> CFU – leading to its intestinal and hepatic colonization – a dominance of G2008b was measured in the gut and D2008b was found earlier in the liver for birds inoculated by both strains. In addition, a transcript level decrease of <italic>JAM2</italic>, <italic>CLDN5</italic> and <italic>CLDN10</italic> at 7 dpi and a transcript level increase of <italic>ZO1</italic>, <italic>JAM2</italic>, <italic>OCLN</italic>, <italic>CLDN10</italic> were observed at 21 dpi for groups of birds having livers contaminated by <italic>C. jejuni</italic>. These discoveries suggest that <italic>C. jejuni</italic> would alter the intestinal barrier function probably to facilitate the hepatic dissemination. By <italic>in vitro</italic> co-culture assay, a growth arrest of D2008b was observed in the presence of G2008b after 48 h of culture. Based on these results, commensalism and competition seem to occur between both <italic>C. jejuni</italic> strains, and the dynamics of <italic>C. jejuni</italic> intestinal colonization and liver spread in broilers appear to be strain dependent. Further <italic>in vivo</italic> experimentations should be conducted to elucidate the mechanisms of commensalism and competition between strains in order to develop adequate on-farm control strategies.</p>