Methicillin-resistant Staphylococcus aureus (MRSA) is an important nosocomial pathogen in humans. It is also being implicated in community-associated infections. Although MRSA infections are rare in pets, they are on the rise. Virulence of the infection in pets can range from mild to life-threatening. Staphylococcus aureus is often a commensal organism and can colonize intact body surfaces. Up to 38% of people carry S. aureus in their nasal passages. It can be an important pathogen and before the invention of penicillin caused mortality rates approaching 90%. Penicillin-resistant strains were soon isolated. Methicillin, which is relatively resistant to β-lactamase, worked for a while, but soon resistant strains were also identified. Clinical MRSA infections have been identified in veterinary patients. Human-to-dog and dog-to-human transmission of MRSA have been reported. Owners of infected animals should be informed of the potential risk of transmission to humans and to other animals in the household. Although risk for disease is low in healthy persons, it is much higher among immune-compromised family members and in health care workers. In most cases, systemic antimicrobial therapy is required to treat MRSA infections. Treatment should be based on in vitro antimicrobial susceptibility testing combined with other animal and drug factors, such as penetration of drug and concentration at the site of infection.

COMMENTARY: Although MRSA infection does not seem to be widespread, it is becoming an important emerging zoonotic disease. Veterinarians should take an active role in understanding disease surveillance, diagnostic testing, and infection control. Animals suspected to be infected or colonized should be treated as infectious, and appropriate isolation procedures should be put in place. Disinfecting cages and the environment should be done systematically and appropriately.

Methicillin-resistant Staphylococcus aureus: An emerging pathogen in small animals. Weese JS. JAAHA 41:150-157, 2005.