CAT and streptococcal infection: Compared with the control group, the serum levels of glutamic oxaloacetic transaminase (GOT), glutamic pyruvic transaminase (GPT), alkaline phosphatase (AKP) and glucose (GLU) in the streptococcal infection group increased significantly, while the levels of total antioxidant capacity (T-AOC), superoxide dismutase (SOD), catalase (CAT) and reduced glutathione (GSH) decreased significantly; observations of pathological sections showed obvious damage to the liver tissue structure in response to streptococcal infection.