My own animals provide frequent fodder for this blog, both good and bad. Rumple’s been featured a few times before, and his latest escapade is a great antimicrobial stewardship case.

Rumple’s an indoor-outdoor cat that we adopted years ago through Guelph Humane Society’s working cat program. He was deemed unsuitable for a household, so we got him as a barn cat, but he migrated from the barn to the deck to the garage to being a part time indoor cat afterall (as I write this, he’s stretched out sleeping on my bed). He’s a big suck who spends a lot of time inside, but wouldn’t tolerate being inside 24/7. That creates some risks.

A week or so ago, we noticed a scab on Rumple’s ear and one on his neck. We figured he’d tangled with something outside (we occasionally see other cats around here, as well as the usual wildlife). No big deal. However, a few days ago, I felt a soft fluctuant swelling on his neck, just past his head. It wasn’t overly painful, there was no inflammation around the site and he seemed perfectly normal otherwise, all of which is consistent with a localized abscess.

Antimicrobials? Nope.

Antimicrobials don’t work well for an abscess. The drugs don’t penetrate the abscess well, and the environment inside the abscess can hinder them from working.

More importantly, we have a much more effective treatment: incision and drainage, as illustrated below.

Since he was systemically healthy and there was no evidence of a tissue infection beyond the abscess, incision and drainage was all he needed. There was a soft spot under a scab that I opened up with a hemostat and we got big gush of pus. (Abscesses can be really rewarding to treat when they drain like that!) I flushed it out quickly (he’d had enough of me at that point), and that was it. It stopped draining quickly so he didn’t need any more wound care. A few days later, the site has a bit of a scab but is otherwise normal (see last picture below).

If I’d given Rumple antimicrobials when I drained the abscess, one might have thought “wow, look how well the antibiotics worked – it cleared up right away,” but this shows that they weren’t needed. However, as clinicians, we often feel a need to “do something,” even though that “something” may not be required. We also tend to be quick to ascribe good responses to what we did, vs what was going to happen anyway.

What percentage of cats in Rumple’s situation would have been treated unnecessarily with an antimicrobial?

• Probably a very high percentage.

Why is that? There are lots of potential reasons:

• Risk aversion
• Habit
• Lack of education on abscess management
• Lack of confidence treating without antimicrobials.
• Veterinarians thinking the client expects it.
• Owners asking for antimicrobials.
• More fear of someone complaining that the veterinarian didn’t use antimicrobials if things don’t go well, than concern about adverse effects of antimicrobials (in the individual or the population).
• It’s easier and quicker to give an antibiotic than to explain to an owner why it’s not being given.

Sometimes, animals do need antimicrobials if they have an abscess, such as when they have concurrent active tissue infection or systemic disease. (Rumple had a soft tissue infection a few years ago, likely also from a bite, but that time he needed antimicrobials.) In most cases, though, cat bite abscesses are discrete abscesses that just need incision and drainage.

Not using antimicrobials is easier on the cat (no need for pilling or injections), easier on the owner (no need to pill the cat, cheaper), and means there are no risks of adverse drug reactions or promoting antimicrobial resistance.

Another question that will come up about this case: Did I culture Rumple’s abscess?

No. There are a few reasons I chose not to do a bacterial culture, but the biggest one is that it doesn’t really matter what bug is present – I’m going to treat it the same regardless with incision and drainage. A culture is more useful if I am going to use a systemic antimicrobial, but since I wasn’t going to, it wouldn’t add any value (apart from satisfying my curiosity). Culture is a really valuable tool that’s underused overall, but it’s also overused in some situations, providing information that’s not needed or that can even be misleading. For your typical abscess that’s easily managed with incision and drainage, it’s pretty low yield.