Fact Sheet: Miscellaneous Mastitis Causing Organisms

Organisms classified as Staph, Strep or Coliform cause the majority of mastitis infections. However there are many other organisms capable of causing mastitis and finding one of these miscellaneous species causing a mastitis infection may be highly significant for a dairy herd.

Nocardia infections

This organism is found through out the dairy environment and on cows. Much of what was written regarding yeast infections applies to nocardia. Similarly the agent enters the udder with the passage of an infusion device. Unfortunately infected cows do not respond to antibiotics and the disease destroys the udder. The organism causes fibrosis of the mammary tissue (woody texture) a pus type discharge and possibly draining tracts. Good infusion technique, proper sanitation of hands and teat-ends, wearing gloves and the use of single use treatment devices is highly effective prevention.

Corynebacterium bovis

As the name suggests this is a common inhabitant of cattle. It is rarely the cause of clinical mastitis as it generally limits its colonization to the teat canal. This agent could be considered a contagious mastitis as it is spread cow to cow at milking. Any udder infection caused by C. bovis is usually mild with small elevations in SCC and a slight reduction in milk production. Treatment with antibiotics is not generally indicated Post milking teat dipping with an effective product and a good program of dry treatment is very effective.

Arcanobacterium pyogenes

These bacteria commonly inhabit wounds on teats and elsewhere. Abscesses and genital tract discharges are also a source. The agent is spread by contact of the teat with contaminated environments in calving areas or dry cow housing. Also the feeding activities of flies may spread the organism. A. pyogenes causes an acute pus forming mastitis that does not respond well to treatment. Once a quarter is infected it is best to destroy the quarter to limit shedding and eventually cull the cow. Fly control is also important to prevent the spread of the organism. Infections with this bacterium are most common in dry cow and heifers just prior to calving and in lactating cow after a teat injury or the use of a teat tube or dilator. A. pyogenes may be more common in warm humid weather.


commonly found in water, damp bedding or on equipment, this tough bug may be splashed onto the teat during washing or picked up from the environment. Pseudomonas are resistant to disinfection and antibiotics causing most infected cows to be culled. Keeping the cows clean and dry and affecting good drainage in yards, barns and loafing areas is helpful in preventing infection as is good milking hygiene.


  • Whether dry cow or lactating cow treatment use a new, single use udder preparation only.

  • Clean teat-end and hands prior to infusion. The use of sterile gloves is recommended.

  • Avoid the use of bulk mastitis treatments. A contaminated bulk supply could infect a large number of cows.

  • Ensure sterility of all infusion equipment, teat tubes, dilators, etc. and only use them after carefully cleaning the teat-end. It is best to avoid the use of this type of equipment altogether.

  • Be sure the milking equipment is working properly.

  • Be sure all milkers are using good technique and proper hygiene.