They occasionally cause serious mastitis problems in individual cows but generally infected cows are not the cause of elevated coliform counts in bulk tank milk. When it rises into the thousands it often means there are dirty zones in the milking system where these bacteria are growing and sending large numbers into the raw milk. Taking Action B acteria counts need to be tracked over time to determine if there are trends of any type. Cooling problems, clinical mastitis or cleaning system failure may be the reason. A trend of increasing counts or long periods of high counts may indicate a different problem.
Higher counts suggest problems with cleaning, sanitizing or milking wet cows.
Maintaining low PI counts requires doing everything required for a low SPC plus a little extra. Strep ag should not be present in bulk milk. Its presence means infected cows. Find them, treat them or cull them. They typically are from exterior locations of the cow including dirty cows.