Milk samples must be taken using aseptic technique and placed on ice or refrigerated immediately. Contaminated samples or mishandling of the sample can lead to misdiagnosis and confusion.

Sampling consideration:

• Composite samples used to screen herd for infected cows.
• Quarter samples when evaluating individual or clinical cows.
• Use bulk tank to screen or monitor herd for contagious mastitis.

Sampling:

• Clean teats ( predip and dry ) before sampling.
• Clean teat end with 70% alcohol using cotton balls, pledgets or wipes.
• Teats must be dry before collection sample. Use a tight sealing vial or tube.
• Discard first milk and collect (midstream (45 degree angle) into a sterile via or tube (5 to 10 ml)
• Store samples on ice or refrigerate until planting. (Freeze, if greater than 48 hours)

Plating Selective Agar:

• Plate milk sample as soon after collecting as possible. Fresh is best.
• Single plate media (ie, blood agar plates) can be divided for each quarter of a cow or divided into half plate for a four quarter composite sample.
• Selective agar triplate (blood agar, TKT agar, MacConkey agar); a single clinical quarter/plate.
• Read selective for coliforms:
  1. MacConkey agar is selective for coliforms
  2. TKT agar is selective for streptococcal organisms
  3. Blood agar will grow all organisms
• Gram staining and other testing are helpful in identifying organisms.

Mastitis Identification Protocol

Selecting Samples