Timing of entry of Streptococcus uberis into the mammary gland of the dairy cow

Abstract

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.

Streptococcus spp. from bulk-tank milk and milking machine teatcups on small ruminant farms, and factors potentially associated with their isolation

“…The bacteria may then possibly colonise the teat-end(s) of the animals milked subsequently, which can potentially lead to an increase in intramammary infections. In a recent challenge study, Hillerton (2020) reported that streptococci could cause clinical mastitis more frequently if infused immediately after milking than at other times in relation to milking. This may possibly be allied to a potential transmission of the bacteria from the teatcups to ewes occurring during milking.…”