Equis ISSN 2398-2977

Staphylococcus aureus

Synonym(s): S. aureus

Contributor(s): Susan Dawson, Richard Walker




  • Family:Micrococcaceae.
  • Genus:Staphylococcus.
  • Species:aureus.


  • Gk:staphule- bunch of grapes;kokkos- grain or berry.
  • Latin:aureus- golden.

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Clinical Effects



  • Inhabits the distal nasal passage, external nares, and skin, especially near mucocutaneous borders such as the perineum, external genitalia and bovine udder.
  • May also transiently inhabit the gastrointestinal tract.


  • Reproduction by binary fission.


  • Spread by direct and indirect contact.
  • Many infections endogenous.
  • Rarely transmitted between species.

Pathological effects

  • Staphylococcusspp produce toxins and enzymes   →   variety of clinical syndromes, eg epidermolytic toxins in porcine exudative epidermitis, and alpha toxin (hemolysin) associated with gangrenous mastitis in cattle.
  • Pyogenic   →   abscess formation.
  • No lasting immunity after recovery.
  • Endogenous or exogenous infection   →   suppurative conditions (in cattle, sheep, goats, pigs, horses, poultry, rabbits, dogs and cats).
  • Wounds, burns, chronic debilitating disease and foreign body, eg suture   →   deep-seated invasive disease.
  • Equine dermatitis (not very common):
    • Lesions 3-5 mm diameter under tack or harness (may be caused by rubbing).
    • Raised nodules with scab.
    • Little pus; some red serous fluid.
    • Long-lasting; difficult to cure.
    • May cause systemic reaction   →   shock, toxemia or septicemia.

Other Host Effects

  • Same asStaphylococcispp   Staphylococcus spp  .
  • Colonizes skin and mucous membranes of mammalian species.


Control via animal

  • Avoid pressure from tack or harness.

Control via chemotherapies

  • Many strains are resistant to penicillin and tetracycline. Penicillinase-resistant penicillins, cephalosporins, chloramphenicol usually effective.
  • Methicillin-resistantS. aureusstrains have been isolated from horses; molecular typing suggests that these differ from human strains.


  • None commercially available.
  • Autogenous bacterin has been used against equine dermatitis.


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Further Reading


Refereed papers

  • Recent references for PubMed and VetMedResource.
  • Weese J S et al (2006) Methicillin-resistant Staphylococcus aureus in horses at a veterinary teaching hospital: frequency, characterization and association with clinical disease. J Vet Intern Med 20 (1), 182-186 PubMed.
  • Weese J S & Rousseau J (2005) Attempted eradication of methicillin-resistantStaphylococcus aureuscolonisation in horses on two farms. Equine Vet J 37 (6), 510-514 PubMed.
  • Scott Weese J et al (2005) Community-associated methicillin-resistant Staphylococcus aureus in horses and humans who work with horses. JAVMA 266(4), 580-583 PubMed.
  • Hartmann F A, Trostle S S, Klohnen A A O (1997) Isolation of methicillin-resistant Staphylococcus aureus from a postoperative wound infection in a horse. JAVMA 211 (5), 590 PubMed.
  • Shimizu A, Kawano J, Ozaki J et al (1991) Characteristics of Staphylococcus aureus isolated from lesions of horses. J Vet Med Sci 53 (4), 601-606 PubMed.
  • Markel M D et al (1986) Cellulitis associated with coagulase-positive staphylocci in race-horses; nine cases (1975-1984). JAVMA 189, 1600-1603 PubMed.