Streptococcus uberis do not colonise the teat canal and appear to invade the mammary gland of the dairy cow by direct entry though the canal. When they enter the mammary gland, and the early resulting processes, are unclear. Experimental infusions of the lactating mammary gland have been made to determine outcomes of infection, mastitis and disease. Infusion of 500 cfu bacteria was made immediately after milking (8 and 16 h intermilking interval) and 1, 4 or 12 h prior to milking. A mastitis resulted from all infusions, probably in response to the skim milk carrier. Infusions post milking resulted in clinical mastitis in more than half of the quarters, whereas infusion 1 h premilking created no clinical mastitis. Infusion 4 or 12 h pre milking resulted in the most severe reactions, with all quarters developing moderate to severe clinical mastitis. This was more rapid with the 4 h pre milking group. The results demonstrate that the initial inflammatory response caused by an invasion of the mammary gland is not necessarily protective against establishment of a pathogen, and that especially the response to invasion in the intermilking interval is often insufficient to prevent infection and/or disease.

中文翻译：

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乳房链球菌进入奶牛乳腺的时间

乳房链球菌不要定植于乳头管，并通过直接进入乳头管似乎侵入奶牛的乳腺。它们何时进入乳腺以及早期产生的过程尚不清楚。已经对泌乳乳腺进行了实验性输注，以确定感染、乳腺炎和疾病的结果。在挤奶后（8 和 16 小时的挤奶间隔）和挤奶前 1、4 或 12 小时立即注入 500 cfu 细菌。所有输液都导致乳腺炎，可能是对脱脂牛奶载体的反应。挤奶后输注导致超过一半的季度出现临床乳腺炎，而挤奶前输注 1 小时未产生临床乳腺炎。挤奶前 4 或 12 小时的输液导致最严重的反应，所有部位都发展为中度至重度临床乳腺炎。挤奶前 4 小时组的速度更快。结果表明，乳腺入侵引起的初始炎症反应不一定能防止病原体的形成，尤其是在挤奶间隔中对入侵的反应通常不足以预防感染和/或疾病。