The emergence and prevalence of MRSA, MRSP, and MRSS in pets and people - Veterinary Medicine
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The emergence and prevalence of MRSA, MRSP, and MRSS in pets and people
Should you be concerned about getting a form of this stubborn infection from your patients—and vice versa? Here's an overview of this increasingly common and concerning bacteria—consider it MRS 101.



MRSA in people

Staphylococcus aureus is often commensal in humans and is carried in (colonizes) the nasal passages of 29% to 38% of people.2,3 The prevalence of MRSA colonization in people in the United States is estimated to be 0.8% to 3.5%, but 30% to 40% of clinical S. aureus organisms isolated from human infections are methicillin resistant, and MRSA is now one of the most common nosocomial pathogens in the world.2,3

MRSA first emerged in the form of hospital-acquired infections within a year of the introduction of methicillin, but it was not until the mid-1980s that this problematic pathogen became a steadily increasing clinical problem. In 2003, a national hospital infection surveillance report revealed that 64.4% of healthcare-associated S. aureus infections in intensive care units were caused by MRSA, compared with 35.9% in 1992.4

Hospital-acquired MRSA is typically associated with resistance to multiple antibiotic classes in addition to beta-lactams, and it is reported to cause increased morbidity and mortality in people compared with methicillin-susceptible staphylococcal infections, usually associated with bacteremia, pneumonia, cellulitis, osteomyelitis, endocarditis, and septic shock.5 Identified risk factors for increased transmission of hospital-acquired MRSA include:

  • Previous antimicrobial therapy (use of fluoroquinolones and cephalosporins has been linked to the emergence of resistance of methicillin-resistant staphylococci6,7)
  • Immunosuppressive disease4
  • Invasive medical instrumentation (e.g. intravenous and urethral catheters, bypass machines, prosthetic devices)4
  • Surgery4
  • Hospitalization4

In the mid- to late 1990s, methicillin-resistant staphylococcal infections that were genetically different from the hospital-acquired MRSA strains (and often susceptible to non-beta-lactam antimicrobials) were identified in healthy people without prior hospital exposure; since then community-associated MRSA has become an increasing problem.8 Although most community-associated MRSA infections have involved skin and soft tissue infections, serious invasive infections have also occurred, and the strains responsible for these infections have now entered the healthcare setting, obscuring the line between community and hospital strains.9 Identified risk factors that increase transmission of community-acquired MRSA include:

  • Crowded living conditions4
  • Shared bathing facilities4
  • Intravenous drug use4
  • Contact with someone else who is colonized or infected with community-acquired MRSA.4

By the numbers: MRSA colonization in veterinary professionals
So how prevalent is MRSA in people that work in veterinary-related settings? See the sidebar "By the numbers: MRSA colonization in veterinary professionals."


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