People are in such close contact with their dogs, cats, and other pets that research shows they often share flora, or tiny bacteria and other microorganisms that inhabit the skin, gut, and even the environment of the home. If you or your pet take an antibiotic or another antimicrobial medication, it can potentially change the flora you both carry. And if your pet is carrying antimicrobial resistant bacteria, which may lessen the efficacy of prescribed medications, you may be, too. 

For decades, experts have been sounding the alarm about the presence and risks of antimicrobial resistance (AMR) in human medicine. AMR occurs when microorganisms, especially bacteria, become resistant to medications designed to eliminate them, such as antibiotics, which target bacteria, and other antimicrobials, which target microbes like parasites, viruses, and fungi. A legislative mandate issued in 2019 required that hospitals have antimicrobial stewardship programs to receive federal funding, such as from Medicaid or Medicare. 

But antimicrobial stewardship in veterinary medicine, specifically with companion animals, is an emerging and evolving field. And veterinary experts at Cummings School of Veterinary Medicine at Tufts University are leading the charge. 

“AMR is the perfect story to demonstrate One Health, which means the health of humans, animals, and the environment are connected. We know antibiotic use in animals can cause resistance to develop in them, which can be shared with their owners and the environment, and the same can happen if antibiotics are used in people with pets,” said Claire Fellman, D.V.M., Ph.D., DACVIM (SAIM), DACVCP, an associate professor at Cummings School and a small animal internist and pharmacologist at the Henry and Lois Foster Hospital for Small Animals. “We have to be mindful of antimicrobial use and resistance across species.”

Antimicrobial Research Across Tufts University

The Stuart B. Levy Center for Integrated Management of Microbial Resistance (CIMAR) is a collaborative and cross-disciplinary initiative with a mission to deliver new and innovative solutions to combat AMR. 

To that end, Fellman teams up with Ian DeStefano, D.V.M., DACVECC, an assistant clinical professor at Cummings School and a specialist with the emergency and critical care service at Foster Hospital for Small Animals, to lead the hospital’s Infection Control and Antimicrobial Stewardship Team (ICAST). 

“In the clinical space, Claire and I focus on trying to promote judicious use of antimicrobials by recommending the appropriate drug and treatment duration and discouraging less appropriate use of antimicrobials, as one tool to help mitigate the emergence or spread of multidrug-resistant bacteria in our companion animal patients,” DeStefano said. “We get consulted on lots of types of cases, but often when people come to us, it's with test results that indicate an infection caused by bacteria that has some level of antibiotic resistance, such as a dog with recurrent urinary tract infections that has been treated with multiple antibiotics and now has a very resistant bacteria found on culture.”

In addition to spearheading antimicrobial stewardship at Foster Hospital, DeStefano and Fellman are also leading efforts to organize other industry professionals with a strong interest in this area. Two years ago, after some grassroots organizing and receiving a grant from the Clinical and Translational Science Award One Health Alliance (COHA), they created the national Companion Animal Antimicrobial Stewards group, or CAAMS, which gathered representatives from veterinary schools and other institutions at its second biennial workshop in Raleigh, North Carolina this May. 

Fellman and DeStefano spoke with Tufts Now about how they advise prescribing veterinarians, what they tell clients about antimicrobials for pets, and what they still hope to learn about AMR. 

Tufts Now: Are there parallels between antimicrobial stewardship in humans and in animals?

Claire Fellman: If you look at a chart of antibiotics used in people compared to all veterinary use, it’ll likely show very different types of drugs—different classes, different agents—because the largest volume of antibiotic use occurs within animal agriculture. But if you look at the comparison charts specifically for dogs and cats versus people, the types of antibiotics used are much more similar—sometimes even the exact same antibiotics.

For example, amoxicillin and clavulanate combined make Clavamox for animals and Augmentin for people. It's one of the top antimicrobials that's prescribed, and it’s literally the exact same drug being prescribed for dogs and cats as for people, in similar proportions and frequencies, and often for similar conditions. 

Sometimes, veterinarians can take expertise from antimicrobial stewardship in humans and apply similar lessons to animals. We look at that a lot when it comes to the duration of treatment. Our antimicrobial treatment courses used to be longer but are now often shortened after many studies in people supported decreased durations. There are a lot of parallels. 

However, unlike human medicine, infectious disease is not a discipline within veterinary medicine. Ian and I recognize that we are fortunate to work at a hospital that has access to consultations with veterinarians who have relevant expertise. But many practice settings don't. With CAAMS, Tufts and other schools in the antimicrobial stewardship space are trying to develop educational tools so that practitioners around the U.S. can say, ‘Of the stewardship messages and resources that are being distributed, how do I really use this infectious disease expertise and apply it to my cases?’ 

How do you consult with prescribing veterinarians about antimicrobial use?

Ian DeStefano: There are a lot of things to consider when a veterinarian asks for advice on a case where they suspect antimicrobial resistance. 

First, I ask, is there, in fact, infection? Sometimes, we might have a case where we're very suspicious of infection, but we haven't proven it, possibly because it's difficult to prove—certain infections require invasiveness in terms of obtaining a sample to test. And yet, the pet might be sick enough that even if a test is still pending, we may start treating with antibiotics. 

Other times, it's a little bit simpler. We know there's a drug-resistant infection because of a bacterial culture test, where a sample was obtained from the patient and sent to the lab to isolate the bacteria. The question is how to approach it and move forward.

We also think about the site of infection. It's a very common scenario for someone to come to me and say that their patient had some sort of wound, or maybe an incision from a previous surgery, and they suspect an infection, so they took a sample of fluid from the area. 

But we know the skin is not sterile whatsoever. Invariably, if you swab the skin on a perfectly healthy pet, you're likely to get a positive result for bacteria if you send that sample to a diagnostic lab, but that doesn’t mean it’s causing disease. For other sites, it’s more clear bacteria isolated are likely the causative agent of the pet's problem.

One of the next questions I ask the prescribing veterinarian is simply, how’s the pet doing? Sometimes the answer changes our decisions about what drugs to use. 

There's a lot of nuances to these cases, and different factors make it complex to know exactly what to do, so consulting can be tricky. But we do our best to get as much relevant information about the pet and its history as possible to try and help clinicians come up with a plan that usually, thankfully, ends up being successful one way or another, which is the important part. 

Q: When are antimicrobials used where, maybe, they shouldn’t be? 

Claire Fellman: When people have pets that go into surgery, sometimes the animal gets an antibiotic to prevent a surgical site infection. We're now recognizing, a lot of those times, that’s unnecessary. But it really does depend on the case and the type of surgery performed, and there are some procedures where antibiotics are needed. As another example, metronidazole has often been prescribed to help with acute diarrhea in dogs, but now studies show it doesn’t make a significant difference, so metronidazole prescribing has gone down at our hospital.  There are many opportunities where we as veterinarians can reduce antibiotic use while still supporting our patients. 

Q: Tell us more about CAAMS and this year’s annual gathering.

Ian DeStefano: Claire and I co-organized the first workshop in the summer of 2023 along with The Ohio State University and the University of Minnesota, where it was held. We brought people together from mostly veterinary academia, but also the Food and Drug Administration and the pharmaceutical industry.

We focused on antimicrobial stewardship programs (ASPs) in a teaching hospital, and how we promote the establishment of ASPs, including a roadmap of how people can establish an ASP at their own institution. We also focused on education, not only because we work in veterinary academia and educate veterinary students, but also because it trickles into other areas, like educating current veterinarians—who have already gone through their veterinary training—on best practices and the ideas of stewardship. 

The third focus area was research efforts. What came out of that meeting was, in our opinion, a very productive and collaborative effort to get people on the same page. Our list of research collaborators and people we speak to routinely for advice has grown tremendously from that. 

We published two manuscripts about the first workshop. One summarizes the meeting itself—what we did and what came out of it—and the second is a summary of ASPs in veterinary teaching hospitals across the U.S. and Caribbean.

With this second iteration, we're building from where we left off at the last meeting. There will be more of a focus on infection prevention and control, as an important cousin of stewardship practices, but still with the same goal, which is mitigating antimicrobial resistance.

That’s the summary of how CAAMS came to be, and it's been super-exciting, and, dare I say, fun.