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Stanford study: Not all dog bites should be treated with antibiotics

Just before the holidays, my husband whisked me off to urgent care because I received some nasty dog bites on both my hands. The incident involved surprise (our new foster dog seemed so sweet!), lightheadedness and nausea from shock, wonderfully caring medical staff, a few stitches, and a prescription for antibiotics.

I had never been bitten by an animal before, and the protocol was new to me. Sure, the wounds looked ugly, but I assumed they could just be stitched up, and I'd heal like the times I accidentally cut myself with a kitchen knife. Turns out, the risk of infection is deemed so high with animal bites that not only are prophylactic antibiotics prescribed as a matter of course, but the doctor was hesitant to use stitches, lest the closed wound become an inflamed pocket of harmful bacteria. After consulting with a plastic surgeon, her compromise was to "tack" it with three or four stitches, where ten or twelve would have been appropriate.

While this was a learning experience for me (in dog behavior as well as medical protocol!), doctors are well aware of bites' potential for infection. However, new research shows that the protocol for dog bites should vary depending on the bite's characteristics, and that routine prescriptions of antibiotics may not be necessary.

The study, conducted by Stanford medical student Meg Tabaka under supervision by James Quinn, MD, a professor of emergency medicine, followed nearly 500 patients who received treatment for dog bites over the past 4.5 years. Their incidence of infection was correlated with two characteristics: puncture wounds and closed wounds. Of the wounds that became infected in the sample, only 2.6 percent were neither punctures nor closed during treatment. The conclusion of the researchers is that puncture wounds and closed wounds are at high enough risk of infection to warrant prophylactic antibiotics. A potential implication is that in other types of wounds, antibiotics may not be necessary - that is, their benefits might not outweigh their risks.

When I contacted Quinn, he answered a few of my questions about the research:

What is it about dog bites that makes them at high risk for infection?

Basically the bacteriology, particularly for Pasturella infection, and the associated trauma and tissue damage. Current practice is to overestimate the incidence of infection and thus over-treat bites with prophylactic antibiotics… [However] a short course for prophylaxis is actually not as dangerous (in terms of resistance, side effects) as a prolonged course for a documented infection.

What counts as a "closed" wound?

I mean any closure. Sutures are even more at risk since they cause further trauma and a foreign body in the wound. The value of loose or tight closure is not well studied. I believe any closure should get extra cleansing and prophylactic antibiotics when it is important to close for cosmetic reasons. Otherwise they should be left open to heal secondarily.

What should readers know about about bites from other animals?

Cats bites rarely cause lacerations and are generally punctures, and thus have higher infection rates with Pasturella as an important organism as well. Bites from wild animals are rare, but when they occur they should usually be treated with prophylactic antibiotics. More importantly, consideration of rabies should be of prime concern.

What's the main message you hope physicians will take from this study?

The true incidence of dog bite infections is likely overstated in the literature and may be based on old data when we may not have routinely cleansed wounds as well. If physicians were more selective, treating just deep punctures, wounds that need closure, and wounds of those who are immunosuppressed or diabetic, that would be a more rational and cost effective approach than just treating all or most dog bites, as is currently being done.

According to the guidelines outlined in the study, my particular bite was a good candidate for antibiotics, as it required sutures, even though they were loose. In any case, I'm grateful to report that I healed up beautifully!

Previously: Is honey the new antibiotic? and Research suggests bacteria from dogs may protect against asthma
Photo by philhearing

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