design: The genomic DNA was extracted from all ExPEC isolates using a commercial DNA Kit (TIANGEN, Beijing, China). The quality and concentration of the bacterial genomic DNA were assessed through electrophoresis on a 1% agarose gel, and analysis was conducted using a NanoDrop2000 system (Thermo Scientific, Waltham, MA, USA) and a Qubit 4 Fluorometer (Thermo Scientific, Waltham, USA). All genomes of the studied E. coli isolates were sequenced through the Illumina HiSseq 2500 platform.