Enriched Enterobacteriaceae was an independent risk factor for acute ischaemic stroke patients in early-stage recovery.MCAO mice showed rapid gut dysbiosis with Enterobacteriaceae blooming, associated with intestinal ischemia and nitrate production.Enterobacteriaceae exacerbates brain infarction by accelerating LPS/toll-like receptor 4(TLR4)-mediated systemic inflammation.Inhibiting Enterobacteriaceae overgrowth by diminishing nitrate generation or inhibiting nitrate respiration alleviates brain infarction. Here, TLR4 is linked to brain infarction.