Equis ISSN 2398-2977

Staphylococcus aureus

Synonym(s): S. aureus

Contributor(s): Susan Dawson, Richard Walker

Introduction

Classification

Taxonomy

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

Etymology

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

Active Forms

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Clinical Effects

Epidemiology

Habitat

  • 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.

Lifecycle

  • Reproduction by binary fission.

Transmission

  • 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

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.

Vaccination

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

Diagnosis

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Further Reading

Publications

Refereed papers

  • Weese J S  et al(2006)Methicillin-resistantStaphylococcus aureusin horses at a veterinary teaching hospital: frequency, characterization and association with clinical disease.J Vet Intern Med20(1), 182-186PubMed.
  • Weese J S & Rousseau J (2005)Attempted eradication of methicillin-resistantStaphylococcus aureuscolonisation in horses on two farms.Equine Vet J37(6), 510-514PubMed.
  • Scott Weese Jet al(2005)Community-associated methicillin-resistantStaphylococcus aureusin horses and humans who work with horses.JAVMA266(4), 580-583PubMed.
  • 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.JAVMA211(5) 590.
  • Shimizu A, Kawano J, Ozaki Jet al(1991)Characteristics of Staphylococcus aureus isolated from lesions of horses.J Vet Med Sci53(4) 601-606PubMed.
  • Markel M Det al(1986)Cellulitis associated with coagulase-positive staphylocci in race-horses; nine cases (1975-1984).JAVMA1891600-1603.

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