IL1A and infection: ELISA results examining the inflammatory response of RAW267.4 cells post‐infection with APEC‐mcr‐1 and its ∆dinB‐mcr‐1 strains revealed that ∆dinB‐mcr‐1 infection significantly reduced the secretion of pro‐inflammatory cytokines IL‐1α, IL‐1β, and IL‐6 (Figure4a–c).