Identification of <i>Campylobacter jejuni</i> genes involved in commensal colonization of the chick gastrointestinal tract

TLDR

Campylobacter jejuni is the leading cause of bacterial gastroenteritis worldwide and commonly colonizes the gastrointestinal tracts of birds, making poultry a major source of human infection. This study sought to identify the bacterial genes required for commensal colonization of the chick gastrointestinal tract, representing one of the first genetic screens for this purpose. The authors employed signature‑tagged transposon mutagenesis on C. jejuni strain 81–176 to isolate mutants with impaired colonization of the chick gut.

Abstract

Summary Campylobacter jejuni is the leading cause of bacterial gastroenteritis in humans in developed countries throughout the world. This bacterium frequently promotes a commensal lifestyle in the gastrointestinal tracts of many animals including birds and consumption or handling of poultry meats is a prevalent source of C. jejuni for infection in humans. To understand how the bacterium promotes commensalism, we used signature‐tagged transposon mutagenesis and identified 29 mutants representing 22 different genes of C. jejuni strain 81–176 involved in colonization of the chick gastrointestinal tract. Among the determinants identified were two adjacent genes, one encoding a methyl‐accepting chemotaxis protein (MCP), presumably required for proper chemotaxis to a specific environmental component, and another gene encoding a putative cytochrome c peroxidase that may function to reduce periplasmic hydrogen peroxide stress during in vivo growth. Deletion of either gene resulted in attenuation for growth throughout the gastrointestinal tract. Further examination of 10 other putative MCPs or MCP‐domain containing proteins of C. jejuni revealed one other required for wild‐type levels of caecal colonization. This study represents one of the first genetic screens focusing on the bacterial requirements necessary for promoting commensalism in a vertebrate host.