Fact Sheet: Coagulase Negative Staphylcocci

The Disease

Coagulase negative staphylococci, hereafter known as CNS may be part of the normal skin bacterial population or live in the environment. A cow may become infected with CNS from her own skin source bacteria or from her environment. Cow to cow transmission is not a major problem with CNS. Cows in first lactation have a higher incidence of CNS infection than older cows. Dry cow infection occurs because the bacteria are always present on the teat skin. This is true for just fresh cows also, a matter of opportunity. If a herd is experiencing a high incidence of CNS infections it suggests post milking teat dipping is failing due to poor technique or use of an ineffective germicide.

The Consequences

Many CNS infections are transient. Infections typically being subclinical with somatic cell counts being roughly two to three times those of an uninfected quarter. Occasionally the SCC will rise to 500,000 cells. CNS are the most frequently cultured organisms from milk samples from well managed herds. Infections with the environmental CNS tend to produce more persistent infections.


Postmilking teat dipping with an effective germicide and treatment of all quarters with a commercial dry cow product after the last milking of the lactation are the primary means of controlling CNS infections. Milking clean dry teats will help reduce the contamination of bulk tank milk with bacteria from the teat surface skin. Dry cow therapy should eliminate up to 90% of CNS infections. New infections will occur during the dry period due to the presence of CNS bacteria on the skin.