A recent study just published in the journal Emerging Infectious Diseases evaluated risk factors for dogs having an infection with methicillin-resistant Staphylococcus aureus (MRSA) versus methicillin-susceptible S. aureus (MSSA). This study, headed by Dr. Meredith Faires, compared dogs with MRSA versus MSSA infections from three different veterinary referral hospitals in Canada and the US. Among the more important findings were the following:
- Staying in a veterinary hospital was not a risk factor for MRSA infection, reinforcing the notion that this is predominantly a community-associated disease in dogs (meaning it typically develops in dogs in the general population).
- Most infections, in both the MRSA and MSSA groups, were skin infections. While serious deeper infections can and do occur, skin and ear infections are very common.
- Prior treatment with antibiotics was associated with development of MRSA versus MSSA infections. Dogs that received any antibiotic within 90 days were approximately 3.8 times as likely to have MRSA versus MSSA infection. Dogs treated with drugs from the fluoroquinolone class of antibiotics were 4.6 times as likely to have MRSA versus MSSA infection.
The association between prior antibiotic use and development of a resistant (i.e. MRSA) infection is not surprising, but it is important to document these events and to be aware of them. Antibiotics are critically important drugs in veterinary and human medicine. They save countless lives, but are also overused and misused frequently, and resistance is a critical problem. Studies such as this demonstrate the need for prudent antibiotic use – use them when needed, but use them properly. Don’t use them when a bacterial infection is not present or unlikely to occur.
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