Guiding drug use, changing practices

Updated August 24, 2020

When veterinarians are considering how to treat infections, AVMA officials hope a new report will help bring a panel of experts into the room.

Dr. Paul J. Plummer, who led the AVMA Committee on Antimicrobial’s development of the soon-to-be-released “Antimicrobial Resistant Pathogens Affecting Animal Health in the United States,” said veterinarians conduct complex evaluations when choosing the best medical option to treat infections. Their decisions become easier with more information, whether it comes from bacterial culture and antimicrobial susceptibility testing or resources such as the forthcoming AVMA report, which will describe trends in resistance by animal species, pathogen, and drug.

“This document gives you that scientific subject matter expertise of individuals in each of these host species,” he said.

As of early July, the AVMA was finalizing edits on the document ahead of the AVMA Virtual Convention 2020, which will be hosted online this year rather than in person, Aug. 20-22. Dr. Plummer plans to host a one-hour session, “AVMA Antimicrobial Pathogens Report,” describing the document and how veterinarians can use it.

Lecturers for other sessions during the convention also plan to describe drug resistance trends, unintended consequences of antimicrobial treatments, and how antimicrobial stewardship could change clinical practice and improve outcomes (see sidebar).

Dr. Plummer, professor of veterinary diagnostic and production animal medicine at Iowa State University College of Veterinary Medicine, said stewardship involves thinking through whether an antimicrobial a veterinarian might choose is likely to be effective. Antimicrobials are important tools for veterinarians to fulfill their professional oaths, he said.

The goal, Dr. Plummer said, is to help veterinarians become aware of certain diseases and bacterial pathogens with concerning levels of antimicrobial resistance, which could affect animal health. Heightened awareness of that potential for resistance could influence treatment decisions.

Manual of resistance patterns

A draft of the AVMA report provided to JAVMA News is formatted like a reference manual, giving overviews in early sections of worrisome trends by animal species and pathogen and, in later sections, technical descriptions with details on prevalence and estimated economic impact, especially among food animal species. In the introduction, the authors describe resistance as a health challenge arising over decades as a result of a lack of investment into developing new generations of drugs.

Antimicrobial use exerts selection pressure that promotes emergence of resistant bacteria, the document states.

Dr. Plummer said the AVMA Committee on Antimicrobials worked for several years to develop practical guidance. Species-based panels, with five to 10 experts each, deliberated for months to determine which pathogens practitioners most often see and what messages would help clinicians.

Committee members agree the document will need updates as more information becomes available, he said.

Dr. Plummer sees a chance to increase awareness of resistance patterns and help veterinarians make informed decisions. That could include posting copies of the one-page overviews of particular pathogens inside clinic pharmacies or carrying those summaries in ambulatory practice trucks, he said.

Dr. Megin C. Nichols, who is the enteric zoonoses activity lead for the Centers for Disease Control and Prevention and serves as an observer and technical adviser to the committee, expects the report will shine light on the impacts antimicrobial-resistant organisms have on the health of animals, whether they are raised for food or living in our homes. She also thinks it will show the need for more research on the effects these organisms have on animals, people, and environments.

She noted the overlap among pathogens of concern between the AVMA report and a CDC report. Multidrug-resistant Campylobacter jejuni, for example, has become a health concern in animals, particularly puppies, and an outbreak sickened both puppies and humans.

The CDC report “Antibiotic resistance threats in the United States, 2019” lists the drug-resistant pathogens and pathogen groups of greatest concern for human health. Those include drug-resistant strains of Acinetobacter, Campylobacter, Enterococcus, and Pseudomonas and members of the Enterobacteriaceae family, each of which the AVMA report lists as concerns for at least some animal species.

The CDC report, published in November 2019, says people in the U.S. develop about 2.8 million antimicrobial-resistant infections each year, and about 35,000 die of those infections.

International health officials call the spread of drug-resistant infections a global crisis. The International Coordination Group on Antimicrobial Resistance, co-chaired by representatives of the World Health Organization and United Nations, reported last year that drug-resistant infections kill about 700,000 people around the world each year, and the group found alarming levels of drug resistance in countries across income levels.

Member countries of the World Organisation for Animal Health (OIE) consider antimicrobial resistance among their top three priorities, along with emerging diseases and animal pandemics, according to an organization report published in spring 2019. Other stakeholders—such as representatives of reference laboratories and OIE collaborating centers—also consider it among their top priorities, along with emerging diseases and zoonoses.

In November 2018, AVMA leaders adopted a joint statement with the Canadian VMA and Federation of Veterinarians of Europe that calls for global surveillance of antimicrobial use and resistance and says veterinarians should maintain oversight of antimicrobial use in animals, among other provisions on regulation of antimicrobial drugs and responsible use.

Dr. Nichols said that, in previewing the AVMA document, she learned more about drug-resistant pathogens in aquatic species, the impact of bovine respiratory disease on the cattle industry, and how veterinarians typically select antimicrobials to treat infections in dogs, cats, and horses. She thinks anyone reading the report could find interesting and surprising information about antimicrobial resistance.

“As a veterinarian reading it, I think there’s some good takeaways and information that folks should just be generally aware of,” she said. “And I know it certainly opened my eyes to some of these pressing issues.”

The report illustrates the limits placed on veterinarians through regulations on antimicrobial administration or drug availability, Dr. Nichols said. In some species, she said, the report highlights that what veterinarians know about certain treatments is extrapolated from human medicine.

“There’s just not a lot of data out there about how we’re treating these infections,” she said. “And there’s also not a lot of data out there about the full impact on animal health of many of these organisms.”

Changing practice through stewardship

The AVMA Virtual Convention 2020 will include discussions on changes in antimicrobial administration to livestock, the consequences of antimicrobial treatment on the gut microbiome, and the potential health benefits of careful antimicrobial use and administration.

Dr. David R. Smith, who is an epidemiologist and professor of beef cattle health and reproduction at Mississippi State University College of Veterinary Medicine, asks that veterinarians imagine how improving antimicrobial stewardship could change clinical practice, a theme he sees across the convention’s sessions on antimicrobial use and resistance. His presentation is on antimicrobial administration for disease prevention, how it differs from administration for disease control, how veterinarians can reduce antimicrobial use by preventing disease, and how they can support the best outcomes for animals and their owners.

Dr. Smith’s work has involved talking with cattle veterinarians and cattle owners about how to prevent common bacterial infections—especially respiratory disease and calf scours—and reduce the need for pharmaceuticals. While his talk likely will include examples from bovine medicine, he said the lessons apply across practice types.

Dr. Smith said he advocates nonpharmaceutical approaches to preventing diseases, which can involve changing production systems to protect animal health. But the most efficient uses of antimicrobials sometimes require administering the drugs in anticipation of disease, he said.

Dr. Cooper Brookshire, who is an epidemiologist and assistant clinical professor of one health and shelter medicine at Mississippi State’s veterinary college, hopes his session on drug resistance among Enterobacteriaceae will help encourage practitioners to adopt more drug stewardship practices.

This family of bacteria includes Klebsiella, which is associated with infections in health care facilities. The family also includes Escherichia coli, Salmonella, Shigella, and Yersinia pestis, which together, in humans, accounted for more than half the infections, hospitalizations, and deaths recorded in the CDC’s FoodNet surveillance during 2019.

“When a practitioner is evaluating a case, they’re thinking about what pathogen they’re treating, they are considering the expected compliance of the owner, what the owner can afford, efficacy,” he said. “My goal is for practitioners to have antibiotic stewardship be part of that decision-making process.”

Using Enterobacteriaceae and trends related to that family of bacteria reported in the scientific literature, he hopes to illustrate the need for considering antimicrobial stewardship in daily practice.

He plans to describe clinical scenarios, analyze decision-making processes, and describe how drug stewardship can influence choices. A dog that has uncomplicated diarrhea but remains happy and retains a healthy appetite likely doesn’t need an antibiotic, he said, but many veterinarians would prescribe one.

Other treatment options probably would have the same results, Dr. Brookshire said.

He also noted the risks of antimicrobial-resistant pathogens crossing between human and veterinary medicine, describing previous presentations in which almost entire audiences agreed they had let their pets lick their faces or sleep in their beds. And he is seeing more frequent reports of carbapenem-resistant bacteria isolated from animals, a trend that demonstrates to him this is a good time to focus on stewardship.

“These prescribing decisions truly are a one-health issue,” he said.