Milk Culture and Sensitivity Testing

What is Milk Culture?

Milk Culture is a laboratory method used to definitively diagnose the causative bacteria behind cases of bovine clinical and sub-clinical mastitis. Laboratories grow the bacteria present in the milk from infected cows and assess the bacterial colonies that grow to determine the underlying cause of infection.

What is Sensitivity Testing?

Sensitivity Testing is a process undertaken to determine the resistance or sensitivity of bacteria cultured from the milk to a predetermined list of antibiotics. 

Advantages of  Culture and Sensitivity Testing!

Culture and Sensitivity results provide the milk supplier and his veterinarian with a useful management tool in choosing the most effective course of action in treating clinical and sub-clinical mastitis. It is essential to know which bacteria are present if such issues are to be resolved in a timely and effective manner (e.g. Staph. aureus, Strep. agalactiae, Strep. uberis). 

When to take Milk Culture and Sensitivity Samples?

Milk Cultures are recommended whenever a herd problem emerges, such as:

  • More clinical mastitis cases than is acceptable.
  • When somatic cell count (SCC) is rising.
  • Prior to dry-off in order to focus dry-cow tube selection

It is recommended that samples are taken from all clinical cases before treatment (as antibiotics in the cow’s system will interfere with the milk culture). Store the samples in freezing conditions and submit them to the laboratory if a cow fails to respond to treatment.

When investigating rising SCC, or prior to dry-off, take samples from individual cows with high SCC. Ensure that the milk comes from the high SCC quarters to avoid a dilution effect. The selection of infected quarters can be focused by using your CMT or by undertaking SCC testing on individual quarters. 

What does Milk Culture and Sensitivity Testing Cost?

The test costs €7.50 per sample with an approximate turn-around time of one week. 

Ensure that the Following Sample Procedure is Observed!

Sampling is the most critical step in the Milk Culture and Sensitivity Testing process. If the sample is compromised by the addition of bacteria from the environment subsequent test results will be deemed meaningless (samples can be compromised in a number of ways, e.g. bacteria from your hands, using non-sterile sample bottles, the external surfaces of the cow’s udder, dust contamination, and sampling through milking-equipment). To avoid contamination ensure that the following is observed:

  • Use sterile sample bottles only.
  • Ensure that the sample bottle remains sealed until you are ready to take the sample.
  • Do not touch the inner surfaces of the bottle or cap at any time.
  • Label the bottle. The cow’s full tag number is required.
  • Use disposable gloves and replace as necessary and always replace between cows.
  • Clean/disinfect the udder.
  • Avoid using water during the cleaning/disinfection as water droplets on the udder can lead to contamination when sampling.
  • Thoroughly dry the udder with disposable paper towels.
  • Check that the teats are fully clean.
  • Thoroughly disinfect the teat ends using 70% alcohol or disinfectant wipes.