You might know the bacteria Staphylococcus aureus by an acronym: Methicillin-resistant Staphylococcus aureus, or MRSA. Methicillin-resistant means that the bacteria doesn't succumb to penicillin and similar antibiotics, so even relatively minor infections become difficult to treat. While canine MRSA is still relatively rare, it does occur. Symptoms of a MRSA infection aren't immediately obvious. Your veterinarian diagnoses MRSA through testing.
Many people carry Staphylococcus aureus in their system with no ill effect. Although it's less commonly carried in canines, the same holds true. Dogs usually carry the bacteria in the nose and anus. In healthy dogs, the bacteria is shed within a few weeks. While an infected dog can transmit MRSA to you or family members, generally by licking, you or an infected person can also transmit it to your dog, according to the American Veterinary Medical Association.
Puppies, older dogs and those with compromised immune systems are at higher risk of contracting MRSA. So are otherwise healthy dogs who share a household with people battling the infection, or with human or veterinary health care workers. Therapy dogs who regularly visit hospitals or nursing homes are also at greater risk of exposure. If your dog has received fluoroquinolones, or broad-based antibiotic medications, in large amounts over his lifetime, his risk for a MRSA infection increases. That's especially true for dogs treated for chronic ear infections, a common site for MRSA to take hold.
An infection with MRSA isn't automatically apparent. It's only when standard antibiotic treatment fails that your veterinarian might realize she's not dealing with garden-variety bacteria. Often, MRSA appears in skin infections, or pyodermas, that are usually easy to cure. It's also known to occur in the lungs, with dogs suffering from pneumonia. Rarely, it appears as a urinary tract, eye, ear or joint infection. As the infection persists despite oral and topical antibiotics, your vet performs a bacterial culture. She might also prescribe oxacillin, an antibiotic, for your dog. If oxacillin doesn't cure the infection, the Staphylococcus aureus infection is diagnosed as MRSA, according to the PetMD website.
Just because your dog is diagnosed with MRSA doesn't mean his condition is hopeless. Treatment requires additional care -- and expense -- and probably a longer convalescence. Your vet will conduct a sensitivity test to determine the best antibiotic treatment for your pet, since common antibiotics won't work. The antibiotic she prescribes is likely to take longer to clear up the infection, cause more side effects and cost more. Skin infections must be cleaned frequently, with any boils or abscesses lanced by your vet, PetMD advises.
- American Veterinary Medical Association: MRSA FAQ
- PetMD: Antibiotic-Resistant Infections in Dogs
- Centers for Disease Control: Methicillin-Resistant and -Susceptible Staphylococcus Aureus Infections in Dogs
- Veterinary Partner: MRSA -- Methicillin-resistant Staphylococcus Aureus
- Texas A&M University Veterinary Medicine and Biological Sciences: Staph infections and Methicillin Resistance in Companion Animals
Jane Meggitt has been a writer for more than 20 years. In addition to reporting for a major newspaper chain, she has been published in "Horse News," "Suburban Classic," "Hoof Beats," "Equine Journal" and other publications. She has a Bachelor of Arts in English from New York University and an Associate of Arts from the American Academy of Dramatics Arts, New York City.