Therapeutic Effects Of Youdele On Mastitis Caused By Staphylococcus Aureus And Group B Streptococcus In Mouse Model

A strain of Staphylococcus aureus and Group B Streptococcus were isolated from the milk of dairy cows suffering from clinical mastitis. Lactating mice were challenged by inoculation of Staphylococcus aureus and Group B Streptococcus suspension through the teat canal to develop mastitis model. The immune response of mammary glands triggered by Staphylococcus aureus and Group B Streptococcus infection and the effect of Youdele on mastitis were studied through CFU counts, histological, histochemical, immunohistochemical techniques and ELISA. The results of this study provided a new idea and way to study natural medicine to treat bovine mastitis.The results show that a peak of colonization in mammary glands (7.66±0.13 lgCFU/g mammary gland tissues) was observed at 24h after challenge and the bacterial number decreased after 24h. The steatosis was investigated at 12h post-challenge and pathology of mammary glands became more serious with the development of mammary infection. Mouse mastitis model was developed at 24h after inoculation of bacteria. It was clearly shown that neutrophils heavily occupied the dilated alveoli. The interlobular blood vessels were characteristic of congestion and the epithelial cells of some alveoli displayed markedly necrotic feature. A significant increase (P<0.01) in the number of mast cells and degranulated mast cells was detected in mammary glands of the model mice compared to the control mice at the indicated timepoints. The number of mast cells and degranulated mast cells increased with the progress of infection. The positive staining intensity of both inducible NO synthase (iNOS) and 3-nitrotynosine (3-NT) increased with the progress of infection and had a significant difference compared to the control group at 48h post-challange. The contents of TNF-αand IFN-γin mammary glands of the model group reached the maxlmum at 6h post-challange and decreased at the mininum 36 h post-challange. Both of them increased at 48h post-challange and reached the maxlmum at 72 h post-challange and degraded at the last time. The content of IL-4 creased the maxlmum at 24h, and degraded the mininum at 36h post-challange. It reached the maxlmum at 48h post-challange second time and increased at the last time.A significant decrease (P<0.05) in the number of bacteria was detected in mammary glands of the treated group mice compared to the model group mice at 12 h~5d post-challenge. The inflammation of mammary glands in treated group appeared to be alleviated. The neutrophil infiltration and congestion of some lobular vessels dramatically reduced in thetreated group. A significant decrease (P<0.01) in the number of degranulated mast cells was detected in mammary gland from the treated group mice compared to the model group mice at 18h,24h,36h,48h, post-challenge. It suggested that Youdele could inhibit the degranulation of mast cells, reduce inflmmatory mediators and block excessive inflammation. Compared to the model group mice, the positive staining intensity of iNOS and 3-NT of the treated group decreased. The mammary immunity of the treated group was enhanced due to the decrease of the level of NO. The contents of TNF-αin mammary gland from the treated group were lower than that in model group at 48h,72h,5d ( P<0.01). The contents of IFN-γin mammary gland from the treating group was significantly higher than that in the model group at 36h~5d post-challenge (P<0.01). The IL-4 levels of treat group were significantly lower than those in the mastitis model group at 24h~5d post-challenge (P<0.01).It is show that Youdele could treat the inflammation through degrade the TNF-α, IL-4 levels and heighten the contents of IFN-γ.Conclusion: Youdele could inhibit bacterial proliferation in mammary glands of model mice. Youdele could improve mammary immunity and reduce mammary inflammation through modulating the secretions of TNF-α, IFN-γ, and IL-4 in mice mastitis model and inhibiting the number of degranulated mast cells. It could also alleviate pathological response and inflammatory symptom of mastitis caused by Staphylococcus aureus and Group B Streptococcus apparently. Youdele could reduce the expression of the iNOS and 3-NT in the mammary gland. Thus, it plays a protective role on experimental mouse mastitis caused by S. aureus and GBS. This data provide a new strategy for the therapy of bovine mastitis.