| The mouse mastitis model induced by Staphylococcus aureus (S. aureus) isolated from dairy cow with mastitis was established successfully in this study. The effect of berberine chloride (Ber) on mammary gland and its inflammation-associated factors were investigated and the mechanism of Ber was included. The result of this study provided a novel thought and method for studying Chinese traditional medicine to prevent and treat bovine mastitis.Establishment of experimental mouse S. aureus mastitis: Lactating 8～10d's BALB/c mice were randomly divided into healthy control group, sterile physiological saline solution (PSS) group and three different doses of inoculating bacteria groups. The mice of healthy control group were not treated. 50uL PSS, 1.0×10~2 CFU/50μL, 5.0×10~2 CFU/50μLor 1.0×10~3 CFU/50μL bacterial suspensions were inoculated into the fourth (abdominal) mammary glands via the teat duct respectively in PSS group or three different doses of inoculating bacteria groups. After 24h of inoculation, all the mice were killed and the mammary glands were harvested for histopathological evalutions, bacterial counts and ELISA for TNF-α, IFN-γlevel. The mammary gland structure was kept integrated, epithelial cells sheded mildly, mild hyperemia in capillary vessel from 1.0×10~2 CFU/50μL inoculating bacteria group. Part of mammary gland structure was distructed severely, some epithelial cells sheded, hyperemia and hemorrhage in capillary vessel, edema and PMN infilitration in the interstitium from 5.0×10~2 CFU/50μL inoculating bacteria group. Pathological damages of mammary gland were more severe from 1.0×10~3 CFU/50μL inoculating bacteria group. The bacterial counts and TNF-α, IFN-γlevel in mammary gland increased followed with amounts of bacterial suspension (P＜0.01) in all the inoculating bacteria groups. The result showed that the mastitis could be established in all the inoculating bacteria groups. But pathological changes of mammary gland were visible in the 5.0×10~2 CFU/50μL group and not severe too much compared with that of 1.0×10~3 CFU/50μL group. It was easy to observe the pathological changes of mammary gland and the effect of medicine. So 5.0×10~2 CFU/50μL was chosed to establish the experimental mouse mastitis model.The bacteriostasis results of the Ber against S. aureus in vitro: MIC and MBC of Ber (＞97%) on S. aureus isolated from dairy cow with mastitis were determined by two fold zdilution method. The result indicated MIC and MBC of Ber were 0.24mg/mL, 0.56mg/mL. The Effect and Mechanism of Ber on Experimental Mouse Staphylococcus aureus mastitis: Lactating 8～10d's BALB/c mice were randomly divided into four groups: (A) PSS group, (B)model group, (C)low dose treatment group and (D)high dose treatment group. 50uL PSS or bacterial suspension containing 5.0×10~2 CFU/50μL of S. aureus were inoculated into the fourth mammary gland via the teat duct in A or B,C,D groups respectively. 0.2mL PSS was injected intraperitoneally into A, B group after Oh, 12h, 24h, 36h of inoculation. 0.2mL 0.5mg/mL ,1.0mg/mL Ber were injected intraperitoneally into C, D group after Oh, 12h, 24h, 36h of inoculation. After 12h, 24h, 36h, 48h of inoculation, the sera were harvested. The mammary glands were harvested for histopathological evalutions, changement of mast cells using modified toluidine blue (MTB) staining, bacterial counts and ELISA for TNF-α, IFN-γlevel. The result showed that low and high dose treatment groups could decrease PMN infilitration in mammary gland after 24h of inoculation compared with that of model group. After 48h inoculation, the structure of the most mammary glands in model group was destructed and PMN reduced gradually. Compared with model group, the pathological damages of mammary gland were mild and a little PMN infilitration in alveoli from treatment groups. After inoculation, bacterial counts of low and high dose treatment groups were lower than that of model group (P＜0.01), bacterial counts of low dose treatment group were higher than that of high dose treatment group (P＜0.05). The amounts of mast cell and degranulated mast cell of model and treatment groups presented ascending trend with time, which were higher significantly than those of PSS group(P＜0.01 ). After 12～48h inoculation, the amounts of mast cell and degranulated mast cell of treatment groups were lower than those of model group, the difference was not significant. TNF-α, IFN-γlevel in mammary gland of model group were higher significantly after inoculation (P＜0.01) , 0.5mg/mL and 1.0mg/mL Ber could decrease TNF-α, IFN-γlevel in mammary gland significantly, and their inhibitory effect was dose-dependent. Serum IFN-γof treatment groups decreased significantly after 24h of inoculation. Serum IFN-γof high dose treatment group was lower significantly than that of model group after 48h of inoculation (P＜0.05 ), low and high dose treatment groups were not different from that of PSS group significantly. The results of the study showed that Ber could inhibit S.aureus growth, decrease PMN infilitration and TNF-α,IFN-γlevel in mammary gland, decrease IFN-γlevel of serum and keep TNF-α, IFN-γlevel stabilization, which could participate in the immune response, inhibit excessive inflammatory reaction, alleviate damages of mammary gland from proinflammatory factors. The study confirmed Ber had protective effect on experimental mouse mastitis induced by S.aureus.Conclusion: It was apt to establish experimental mouse mastitis by inoculating 5.0×10~2 CFU/50μL S. aureus into mammary gland via the teat duct. Ber could not only inhibit S. aureus isolated from dairy cow with mastitis in vitro, but also inhibit S. aureus growth in mammary gland of mice. Ber could alleviate pathological response and inflammational symptom of mouse S. aureus mastitis apparently. Ber had protective effect on experimental mouse mastitis induced by S. aureus, which provided a novel thought and method for researching new medicine to prevent and treat bovine mastitis.
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