This study investigated intestinal oxidative damage caused by F18+Escherichia coliand its amelioration with antibacterial bacitracin fed to nursery pigs. Thirty-six weaned pigs (6.31 ± 0.08 kg BW) were allotted in a randomized complete block design. Treatments were: NC, not challenged/not treated; PC, challenged (F18+E. coliat 5.2 × 109CFU)/not treated; AGP challenged (F18+E. coliat 5.2 × 109CFU)/treated with bacitracin (30 g/t). Overall, PC reduced (p< 0.05) average daily gain (ADG), gain to feed ratio (G:F), villus height, and villus height to crypt depth ratio (VH:CD), whereas AGP increased (p< 0.05) ADG, and G:F. PC increased (p< 0.05) fecal score, F18+E. coliin feces, and protein carbonyl in jejunal mucosa. AGP reduced (p< 0.05) fecal score and F18+E. coliin jejunal mucosa. PC reduced (p< 0.05)Prevotella stercoreapopulations in jejunal mucosa, whereas AGP increased (p< 0.05)Phascolarctobacterium succinatutensand reduced (p< 0.05)Mitsuokella jalaludiniipopulations in feces. Collectively, F18+E. colichallenge increased fecal score and disrupted the microbiota composition, harming intestinal health by increasing oxidative stress, and damaging the intestinal epithelium, ultimately impairing growth performance. Dietary bacitracin reduced reduced F18+E. colipopulations and the oxidative damages they cause, thereby improving intestinal health and the growth performance of nursery pigs.