Abstract: The assay was aimed to investigate the effect of Streptococcus agalactiae on oxidative damage in mice liver and the beneficial effect of N-acetylcysteine against the damage. Forty adult mice were divided into 4 groups (control, NAC, S.agalactiae and NAC+S.agalactiae) randomly. Colorimetry was used to detect the content of MDA and the activities of GSH-Px, GST and POD. The results showed that, compared with the control group, there were extremly significant reductions in the activity levels of GSH-Px, GST and POD (P<0.01) accompanied by a extremly significant increase in the MDA content (P<0.01) in bacteria infected group; extremly significant increases in the activity levels of GSH-Px, GST and POD (P<0.01) accompanied by a extremly significant reduction in the MDA content (P<0.01) in NAC group.Compared with S.agalactiae group, extremly significant increases in the activities of GSH-Px, GST and POD (P<0.01), and extremly significant reduction of the MDA content (P<0.01) could be observed in NAC+S.agalactiae group, but when it came to control group, extremly significant reduction in the activities of GSH-Px, GST and POD (P<0.01), and extremly significant increase of the MDA content (P<0.01) could be observed. Thus, the results suggested that infection of Ⅰa S.agalactiae isolated from bovine could induce oxidative damage in mice liver, and NAC (100 mg/(kg·BW)) pretreatment could enhance the activities of GSH-Px, GST and POD, and decrease the MDA content to reduce the damage degree.

Key words: N-acetylcysteine; serotype Ⅰa; Streptococcus agalactiae; oxidative damage