Methicillin-resistant Staphylococcus pseudintermedius (MRSP) is becoming a huge problem in dogs (and to a lesser degree cats). I think it can easily be called an epidemic, and probably even a pandemic, considering the degree of spread, the massive increase in cases and the international distribution of this multidrug-resistant bacterium.

Public health concerns regarding MRSP have received attention because of the huge problem with MRSA (methicillin-resistant Staphylococcus aureus) in people. My line with S. pseudintermedius in general is that while there are only periodic reports of infections in people, exposure to this bacterium is very common, since it is carried by a large percentage of healthy dogs. Given the frequent exposure and very small number of infections, it’s not a particularly pathogenic bacterium for people. The same should apply for MRSP, since methicillin resistance doesn’t’ make it inherently any more able to cause disease, it just makes it harder to treat. However, I always add the statement that, while the risk is pretty low, I’d rather not have an infection with a highly drug resistant bacterium, so we need to pay attention and try to reduce the risk of transmission.

A paper in an upcoming edition of the Journal of Antimicrobial Chemotherapy (Stegmann et al 2010) shows that these concerns are not unfounded. This report, from Switzerland, described an MRSP infection in a person that developed after sinus surgery. The bacterial strain that was involved was sequence type 71 (ST71), the predominant strain found in dogs in Europe. The affected person had a dog with various health problems, but unfortunately the dog was euthanized (presumably not because of the person’s infection) before samples could be taken to see if it carried the same strain. Since we know that S. pseudintermedius can move between pets and their owners (although usually without causing any problems), it’s reasonable to assume that the dog was the source of infection here.

More information about MRSP and MRSA can be found on the Worms & Germs Resources page.

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