Which organism is commonly associated with mastitis and skin infections and is frequently found in the environment?

• A. Proteus vulgaris
• B. Escherichia coli
• C. Streptococcus spp.
• D. Staphylococcus aureus

Answer: (D)

Staphylococcus aureus is a common culprit because it readily colonizes skin and mucous membranes and can persist in the environment, making it easy to spread between animals and stay on surfaces like bedding or milking equipment. It’s a gram-positive cocci that often forms biofilms, helping it survive harsh conditions and continue to cause infection over time. This organism is well known for causing contagious mastitis in dairy cattle, transmitted during milking from affected to healthy udders, and it also readily causes skin infections such as abscesses and dermatitis in various species. The other organisms have different typical roles—for example, some are more associated with environmental sources of mastitis or with urinary and wound infections, and they don’t fit the combination of mastitis, skin infections, and frequent environmental presence as cleanly as Staphylococcus aureus.