Attack of the MRSA

We hear less about it on the news these days (due to the arrival of an attention-seeking princess calling itself COVID), but MRSA is still a pretty big name in medical circles. It’s pronounced “Mersa”, but the letters of its given name stand for “methicillin-resistant Staphylococcus aureus”. Staph aureus is a pretty large family, with some members that are relatively weak and easy to drive away and some members that are invulnerable even to very strong drugs, like methicillin. Perhaps obviously, the antibiotic-resistant ones (MRSA) are the ones to watch.

Drug-resistant infections are being diagnosed more and more these days. It’s very possible that your pet could end up with this condition. It’s good to have a little background knowledge of the situation, especially since you won’t be able to get any human health advice from your vet (against the law, don’t you know!).

First, be aware that there are trillions of bacteria on and in everyone, including, of course, your dog and cat. These aren’t just hitchhikers; they’re actually critical for our well-being and continued survival. The ones that live on us all the time are almost always friendly, but even they can get too big for their britches if something gets out of whack in their environment. A perfect example is when your dog eats something different from his normal diet (like...on Thanksgiving...) and breaks with diarrhea the next day. You didn’t give him anything poisonous, contaminated, or spoiled; it’s just that his gut bacteria weren’t ready for an abrupt and unannounced change in their fodder. One population dominates the others, and some contentious squabbling ensues. The fallout is messy, uncomfortable stools for your friend. This same sequence will occur when your pet has an insult to the skin, most commonly via allergic disease. The environment on allergic skin is no longer well-controlled, and a previously friendly bacteria may jump into the spotlight, causing redness, itching, and hair loss. On a dog, the culprit is usually not Staph aureus but Staph pseudointermedius, although they are like two peas in a pod. The aureus family has a few MRSAs, and the pseudointermedius clan has a few black sheep of its own. You could call them MRSPs… but it’s a lot harder to say out loud. They behave the same. 

Methicillin-resistant Staphs of whatever extraction are not easy to spot. This skin infection looks like every other skin infection on every other allergic dog—itchy and scaly. It’s not the prettiest thing in the world, but it’s not something that would turn your stomach. We can only pinpoint these tough guys by submitting a sample to the diagnostic lab, a special test that is usually only recommended if the skin fails to heal with “normal” antibiotics. So MRSA (or MRSP) could be crawling all over your itchy dog (or even your normal-looking dog!) right now. It can not be cured with normal antibiotics. Is it time to panic? Nope, not yet. Check our next post for how you will calmly handle the presence of a drug-resistant organism in your home. 

Dr. M.S. Regan