The majority of bacterial skin infections in dogs and cats are caused by an organism called Staphylococcus pseudintermedius. This specific type of Staph. is actually part of the normal bacterial flora of the skin in dogs and cats. Staph. pseudintermedius can be found in healthy dogs and cats, on their skin, in their ears, and even in their mouths. Staphylococcal skin and ear infections in dogs and cats are considered opportunistic infections, meaning these normal skin/ear inhabitants only cause an infection when they have an opportunity to do so. These opporunities arise when the skin is affected by another disease process such as allergies, or when the immune system is not fully functional (immune suppression).
Staphylococcus aureus is a different species of Staphylococcus. It can be part of the normal skin flora in some people. Staph. auerus is not considered normal flora in dogs and cats. MRSA stands for methicillin resistant Staphylococcus aureus. Methicillin resistance is a term that indicates resistance to a large group of antibiotics called beta lactams. The beta lactam group of antibiotics includes several well known antibiotics such as amoxicillin, cephalexin, and others. Beta lactam antibiotics such as cephalexin are often prescribed for treating skin infections. Any type of Staph. can aquire this type of antibiotic resistance, so the term “methicillin resistant” can be used to describe any Staph. that becomes resistant to the beta lactam antibiotics.
Antibiotic resistance is diagnosed based on bacterial skin culture and antibiotic susceptibility testing. This is a simple and painless test; once the sample from your pet is submitted, it takes about 3-5 days to receive test results. When we culture antibiotic resistant Staph. skin infections in dogs and cats, the most common bacteria grown is methicillin resistant Staphylococcus pseudintermedius, or MRSP. True MRSA skin infections in dogs and cats are actually pretty rare. Our dermatologists here at Animal Dermatology & Allergy only culture MRSA from our patients at most once every couple years. MRSP infections, on the other hand, are something that we diagnose more often.
It is very important to remember that not all methicillin resistant Staph. organisms are MRSA! This distinction is important because Staph. aureus is adapted to live on humans, whereas Staph. pseudintermedius is not. This means that MRSA infection in a pet does pose a slightly higher risk for transfer of the infection to humans as compared with MRSP infection in a pet. However, the risk to humans is still considered low for both MRSP and MRSA infections in pets. Remember that Staph. skin infections in both people and animals are considered opportunistic infections.
If your pet is diagnosed with a methicillin resistant Staph. skin infection, there are some simple precautions you can take. Excellent handwashing hygiene practices are probably the most important step in reducing the risk of transferring Staph. from your pet to yourself. Additionally, you should minimize contact with the infected areas on your pet. Please click on the links below for some great information about MRSP and MRSA, as well as a more detailed list of precautions that can be taken in case your pet is diagnosed with one of these infections. If you have any special medical needs or health conditions, it is always a good idea to consult with your physician about specific recommendations pertaining to your personal situation. Please check out last month’s blog post for more information on treating bacterial skin infections in dogs and cats. The links below will also take you to some excellent information on MRSP and MRSA infections in pets.