In order to further investigate whether the exogenous IL-17A treatment also plays a role in eliminating S. agalactiae, the same method was used to inject cytokine IL-17A into mice through their tail veins at 24 h before or 6 h after S. agalactiae infection, and the bacterial load of each major organ was detected at 48 h after infection. This evidence concerns the gene IL17A and infection.