When I talk about methicillin-resistant Staphylococcus pseudintermedius (MRSP), I usually say that the human health risks are low because human infections are very rare. However, rare doesn’t mean it can’t happen, as demonstrated by a case report entitled "Beware of the Pet Dog: A Case of Staphylococcus intermedius Infection" published in the American Journal of Medical Sciences (Kempker et al 2009).
This paper reports about a post-operative sinus infection in a 28-year-old woman. Cultures were taken and the bacterium was initially misidentified as a coagulase-negative Staphylococcus. It was then misidentified as S. aureus, and finally determined to be S. intermedius. In reality, that’s probably another misidentification because the bug almost certainly was truly S. pseudintermedius. (It’s become clear over the past couple years that S. intermedius is basically non-existent in dogs and that what has been called S. intermedius in the past is truly S. pseudintermedius).
It’s important to remember that human infection with S. pseudintermedius is a rare event. Whenever you see a single case reported, you know it’s a pretty uncommon or novel event. Further, this was a post-operative infection, not a spontaneous infection occurring in a low-risk person. At the same time, we need to make sure we don’t completely ignore the potential risks. While the risk of transmission of S. pseudintermedius (including MRSP) seems to be very low, we shouldn’t ignore it completely. Isolation and other strict measures aren’t indicated when dealing with a pet with S. pseudintermedius infection, but general attention to basic hygiene practices and avoiding contact with the infected site is still a good idea.