ISSN 2398-2969      

Methicillin-resistant Staphylococcus aureus


Synonym(s): MRSA, S. aureus




  • Family: Micrococcaceae.
  • Genus: Staphylococcus.
  • Species: aureus.
  • Carries genes for methicillin resistance.


  • Gk: staphyle - bunch of grapes; coccus - grain or berry; Latin: aureus - golden.

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Clinical Effects



  • Inhabits the distal nasal passages, external nares, and skin, especially near mucocutaneous borders such as the perineum, external genitalia and bovine udder.
  • May also transiently inhabit the gastrointestinal tract.
  • Humans and animals can be healthy carriers shedding MRSA from the nose and mouth.


  • Reproduction by binary fission.

Pathological effects

  • Staphylococcus spp produce a number of toxins and enzymes → variety of clinical syndromes, eg epidermolytic toxins in porcine exudative epidermitis (due to S. hyicus) and alpha toxin (hemolysin) associated with gangrenous mastitis in cattle.
  • Pyogenic → abscess formation.
  • No lasting immunity after recovery.
  • Wounds, burns, chronic debilitating disease and foreign body, eg suture → deep-seated invasive disease.
  • Endogenous or exogenous infection → suppurative conditions (in cattle, sheep, goats, pigs, horses, poultry, rabbits, dogs and cats).
  • MRSA can be associated with post-operative infections following nosocomial infection.

Other Host Effects

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


Control via chemotherapies

  • All MRSA strains are resistant to penicillins.
  • Antibacterial choice should be based on sensitivity testing.


  • None commercially available, although improved understanding of pathogenesis could lead to vaccination possibilities in the future.

Other countermeasures

  • Hygiene in veterinary practices is important to prevent spread of MRSA.
  • Evidence suggests some animal infections may be from humans via reverse zoonosis; adequate hand washing before touching patients is important.


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Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Crémieux A C, Saleh-Mghir A, Danel C et al (2014) α-Hemolysin, not Panton–Valentine leukocidin, impacts rabbit mortality from severe sepsis with methicillin-resistant Staphylococcus aureus osteomyelitis. J Infect Dis 209 (11), 1773-1780 PubMed.
  • Paterson G K, Larsen A R, Robb A et al (2012) The newly described mecA homologue, mecALGA251, is present in methicillin-resistant Staphylococcus aureus isolates from a diverse range of host species. J Antimicrob Chemo 67 (12), 2809-2813 PubMed.
  • Lin Y, Barker E, Kislow J et al (2011) Evidence of multiple virulence subtypes in nosocomial and community-associated MRSA genotypes in companion animals from the upper midwestern and northeastern United States. Clinical Med Res 9 (1), 7-16 PubMed.
  • Leonard F C, Abbott Y, Rossney A et al (2006) Methicillin-resistant Staphylococcus aureus isolated from a veterinary surgeon and five dogs in one practice. Vet Rec 158 (5), 155-159 PubMed.
  • Weese J S, Dick H, Willey B M et al (2006) Suspected transmission of methicillin-resistant Stapylococcus aureus between domestic pets and humans in veterinary clinics and in the household. Vet Microbiol 115 (1-3), 148-155 PubMed.
  • Baptiste K E, Williams K, Williams N J et al (2005) Methicillin-resistant staphylococci in companion animals. Emerg Infect Dis 11 (12), 1942-1944 PubMed.
  • Weese J S, Archambault M, Willey B M et al (2005) Methicillin-resistant Staphylococcus aureus in horses and horse personnel, 2000-2002. Emerg Infect Dis 11 (3), 430-435 PubMed.
  • Boag A, Loeffler A, Lloyd D H (2004) Methicillin-Resistant Staphylococcus aureus isolates from companion isolates. Vet Rec 154 (13), 411 PubMed.
  • Duquette R A & Nuttall T J (2004) Methicillin-resistant Staphylococcus aureus in dogs and cats: an emerging problem? JSAP 45 (12), 591-7 PubMed.
  • Owen M R, Moores A P & Coe R J (2004) Management of MRSA septic arthritis in a dog using a gentamicin-impregnated collagen sponge. JSAP 45 (12), 609-612 PubMed.
  • van Duijkeren E, Wolfhagen M J, Box A T et al (2004) Human-to-dog transmission of Methicillin-resistant Staphylococcus aureus. Emerg Infect Dis 10 (12), 2235-7 PubMed.
  • Manian F A (2003) Asymptomatic nasal carrriage of mupirocin, methicillin-resistant Staphylococcus aureus (MRSA) in a pet dog associated with MRSA infection in household contacts. Clin Infect Dis 36 (2), e26-28 PubMed.
  • Seguin J C, Walker R D, Caron J P et al (1999) Methicillin-resistant Staphylococcus aureus outbreak in a veterinary teaching hospital: Potential human-to-animal-transmission. J Clin Microbiol 37 (5), 1459-1463 PubMed.
  • Tomlin J, Pead M J, Lloyd D H et al (1999) Methicillin-resistant Staphylococcus aureus infections in 11 dogs. Vet Rec 144 (3), 60-64 PubMed.
  • Hartmann F A, Trostle S S & Klohnen A A (1997) Isolation of methicillin-resistant Staphylococcus aureus from a postoperative wound infection in a horse. J Am Vet Med Assoc 211 (5), 590-2 PubMed.
  • Shimizu A, Kawano J, Yamamoto C et al (1997) Genetic analysis of equine methicillin-resistant Staphylococcus aureus by pulse-field gel electrophoresis. J Vet Med Sci 59 (10), 935-937 PubMed.
  • Hoekstra K A & Paulton R J (1996) Antibiotic sensitivity of Staphylococcus aureus and Staph. intermedius of canine and feline origin. Letters in Applied Microbiology 22 (3), 192-194 PubMed.
  • Cefai C, Ashurst S & Owens C (1994) Human carriage of methicillin-resistant Staphylococcus aureus linked with pet dog. Lancet 344 (8921), 539-540 PubMed.

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