What is 'methicillin resistance' (e.g., MRSA)?
Both humans and animals normally carry and are routinely exposed
to staphylococcal bacteria without harmful effects. Dogs and cats
normally have Staphylococcus pseudintermedius on their skin, while
people and some horses tend to have Staphylococcus aureus. Some
Staphylococcus bacteria have acquired a trait (usually after
repeated antibiotic exposure) called 'methicillin resistance'
making them resistant to commonly used antibiotics, hence more
difficult to treat. When veterinary patients have been exposed to
multiple courses of antibiotics, when 'standard' antibiotics fail
to improve signs of bacterial infection, or when deep forms of
bacterial infections are present, dermatologists will perform a
culture of the patient's skin sores to identify the type of
bacterial infection and to determine if 'methicillin resistant'
bacteria are present. The results of the skin culture allow the
dermatologist to select the most appropriate antibiotic for the
infection at hand. When 'methicillin resistance' is conferred to
Staphylococcus aureus and Staphylococcus pseudintermedius the
acronyms 'MRSA' and 'MRSPi' are used, respectively. Although not
common, MRSPi is more prevalent in companion animals than people.
Similarly, MRSA occurs more often in people (and occasionally
horses) than in dogs and cats. While transfer of bacteria from
human-to-pet or pet-to-human has been reported, this is not a
common occurrence. Nevertheless, following are some simple
guidelines that may help limit the spread of methicillin-resistant
staphylococcal bacteria that could possibly cause health problems
in humans and unaffected pets. Please keep in mind, Staphylococcus
aureus (and thus MRSA) primarily causes bacterial infections in
people, while Staphylococcus pseudintermedius (and thus MRSPi) is
predominantly a bacterial pathogen of dogs and cats.
- Keep young children and immunocompromised people (cancer
patients, HIV/AIDS, patients receiving immunosuppressive drugs)
away from the affected pet. When this is not feasible, make sure
these individuals wash their hands after touching the affected
- Completely finish antibiotics as prescribed to your pet and
return for follow-up examinations. If topical treatments were
prescribed, use them as recommended remembering to wash your hands
- Underlying medical or surgical conditions responsible for the
bacterial infection must be sought and managed for ultimate
infection resolution (and prevention of relapse).
- Wash hands and/or use alcohol-based hand sanitizers after
handling the affected pet and his/her bowls, cage, and toys.
Additionally, wash your hands before and after trips to the
restroom. Remember everything your elders taught you about washing
your hands (e.g., wash your hands before food preparation, use
soap, avoid splatter, gently scrub all surfaces of your hands
during the time it takes you to sing "Happy Birthday to You" twice,
dry your hands off).
- Regularly pick up stool (dogs) or scoop litterbox (cats) of the
affected pet and dispose of it in the trash can.
- Wear gloves when topically treating the affected pet's
- Keep open draining wounds of the affected pet covered.
- Keep personal wounds covered and protected.
- Do not allow the affected pet to lick the face or wounds of
- Do not share the same bed as the affected pet.
- Do not share towels or linens with the affected pet.
- Wash and heat dry affected pet's bedding/laundry separate from
human clothing and linens.
- Do not allow the affected pet to serve as a "therapy animal" in
human health care facilities.
- In an attempt to limit the spread of infection, try to avoid
pet daycare and public dog parks until the affected pet is cleared
of the infection.
- Consult with your personal physician if you develop skin
lesions/sores (e.g., pimples, boils, swellings) or have concerns
about your personal health.
To find out more about MRSA and MRSPi, please download the MRSA Information
Brochure or visit the Worms & Germs Blog .