Identification of Avian pathogenic Escherichia coli genes that are induced in vivo during infection in chickens.

Avian pathogenic Escherichia coli (APEC) is associated with extraintestinal infections in poultry causing a variety of diseases collectively known as colibacillosis. The host and bacterial factors influencing and/or responsible for carriage and systemic translocation of APEC inside the host are poorly understood. Identification of such factors could help in the understanding of its pathogenesis and in the subsequent development of control strategies. Recombination-based in vivo expression technology (RIVET) was used to identify APEC genes specifically expressed during infection in chickens. A total of 21 clones with in vivo-induced promoters were isolated from chicken livers and spleens, indicative of systemic infection. DNA sequencing of the cloned fragments revealed that 12 of the genes were conserved E. coli genes (metH, lysA, pntA, purL, serS, ybjE, ycdK [rutC], wcaJ, gspL, sdsR, ylbE, and yjiY), 6 of the genes were phage related/associated, and 3 genes were pathogen specific (tkt1, irp2, and eitD). These genes are involved in various cellular functions, such as metabolism, cell envelope and integrity, transport systems, and virulence. Others were phage related or have yet-unknown functions.