What Does a Rise in Antimicrobial Resistance Mean?

This article presents data from the report as well as findings from industry research exploring practitioner’s current attitudes toward antimicrobial resistance (AMR). Future articles will explore the implications of AMR for veterinary practitioners and discuss strategies for improving guideline concordance in daily practice.

Implications of Antimicrobial Resistance for Companion Animal Practice

Antimicrobial resistance (AMR) arises when bacteria develop the ability to grow in the presence of antimicrobial drugs. This phenomenon is a natural evolutionary process of bacteria but develops more rapidly through misuse and overuse of antimicrobials.¹ Resistance minimizes the medication options to treat bacterial infections and can challenge veterinarians’ ability to provide effective therapy.

Antimicrobial-resistant bacteria pose disease management concerns not only because resistant organisms can be directly transmitted between hosts, but also because resistance may be transmitted between bacterial species. Evidence indicates that antimicrobial-resistant bacteria are transmitted bidirectionally between humans and household animals. This has implications for the health of companion animal patients, their owners, and their caretakers. Infection with resistant organisms can lead to longer and more severe infections, increased mortality, and higher costs for treatment.^1,2 The growing threat of AMR has contributed to an increased scrutiny of antibiotic use practices in both human and veterinary medicine (Figure 1).

Given the importance of antimicrobial drugs in combatting infectious disease, the veterinary profession will undoubtedly continue to use antimicrobials to promote animal health. However, given the implications for companion animal veterinary practice and public health, antimicrobial use will ideally become more judicious and specific to minimize AMR.

Implications for Veterinarians

A large-scale implication of an increase in the incidence of antimicrobial-resistant infections is the potential for heightened scrutiny of antibiotic use in veterinary medicine, resulting from increased public awareness of AMR. Situations coming under particularly close inspection might include the use of antimicrobial drugs where not indicated; the administration of inappropriate drugs for a given condition; and prescription of antimicrobial drugs with inappropriate dosages, frequencies, or treatment durations.²

As evidenced by regulations on antimicrobial use in human and food animal medicine, it is also conceivable that companion animal veterinarians could be subject to restrictions on the types of antimicrobial drugs available for use in their patients, regulations around the use of specific drugs, and/or the requirement for approval to use certain drugs.³ Although directed primarily at drug manufacturers and distributors, legislation to ensure medicines are safe, effective, and of assured quality could certainly have consequences in the veterinary clinic, including changes in pricing, accessibility, and availability that would affect the use of certain drugs in treatment protocols.¹ Additionally, the World Health Organization (WHO) has suggested optimizing the use of antimicrobial medicines in animal health through training or accreditation of health professionals to align with national legislation. This could include the creation of regulations around the licensing, distribution, and use of antimicrobial drugs and regulatory actions to preserve new antibiotics.¹ It also implies that regulated use of antimicrobials in companion animal medicine, including greater control over dispensing rights, could become a reality.

In the face of the rise of AMR, advancement in the development of new drugs has been minimal. No major new class of antibiotics has been discovered since 1987, and few antibacterial agents are in development. As antimicrobial-resistant infections become more prevalent in companion animal practice, the consequences of infection with resistant microorganisms may include¹:

• Longer duration of illness (refractory to normal treatments)
• Increased mortality
• Prolonged treatment or hospitalization
• Higher costs of care

Evidence of the threat of AMR to veterinary and public health can be found in the recent discovery of a multidrug-resistant strain of Salmonella species infecting a cat presented to an Australian veterinary clinic for an upper respiratory tract infection.⁴ The strain was resistant to approximately 9 classes of antimicrobials, including carbapenems, which are frequently a last line of defense against multidrug-resistant bacterial infections in humans. The infected cat was ultimately euthanized, and 3 of 8 other cats being treated at the clinic for unrelated illnesses subsequently tested positive for the bacterium, indicating that it was highly transferable. This is just a single example; the WHO reports that AMR is present worldwide, and drug-resistant bacterial strains include Escherichia coli, Staphylococcus aureus, and Mycobacterium tuberculosis.⁵

Last, but certainly of crucial importance, is the risk for transmission of antimicrobial-resistant infections from animals to their owners and caretakers, whether by zoonotic spread of transmissible disease or through transference of resistance among bacterial species. Resistant Staphylococcus pseudintermedius was transmitted from pet to owner in Spain,⁶ and numerous multidrug-resistant zoonotic bacteria have been encountered in companion animal practices with the potential to be spread bidirectionally between humans and their pets.⁷ These reports provide evidence that companion animals provide a source of antimicrobial-resistant infections to—and are at risk for contracting them from—humans, making prevention or minimization of zoonotic spread a critical consideration for companion animal veterinarians.

Implications for Clients

AMR has important implications for veterinary clients as well. In the interest of promoting good compliance within a successful veterinarian–client/patient relationship, veterinarians should consider these implications in decision-making and client communications.

Many of the issues that affect veterinarians will be of equal or greater concern for clients because they directly affect their pet and finances. These issues include less effective treatments for infections, which could ultimately lead to worse outcomes, with greater morbidity and mortality. In addition, decreased effectiveness of available treatments and prolonged therapy are likely to result in higher veterinary bills. The WHO has shown that AMR is a drain on the global economy, with economic losses due to higher costs of treatment in human medicine. Although the significance of these costs in companion animal medicine is likely to be lower, the effect on the individual owner is likely to be more substantial.¹

Finally, the reality of the risk for AMR transmission between clients and their pets is a topic that cannot be neglected in educating clients on appropriate antimicrobial use.^6,7 In discussions of treatment options and plans with clients, conveying these longer-term implications may help improve client compliance.

Summary

A major challenge in the judicious use of antimicrobials can be the discrepancy between the visible and invisible effects on patient outcomes and resistance development, respectively. In the short term, immediate patient needs and client expectations can make the dispensation of antimicrobial drugs the easier solution. This may provide coverage in case of infection and avoid the hassle and burden of a client returning later for a prescription if preventive and supportive measures have not been effective. These effects are visible outcomes of antimicrobial use and occur relatively quickly after a patient presents to the veterinarian, so they are more likely to be associated in the minds of the veterinarian and the client.

The invisible consequences of AMR are the public health impacts, drug efficacy, and cumulative patient outcomes. Although serious, these consequences are often removed, both temporally and spatially, for the veterinarian and client, and therefore are harder to balance against the immediate, visible results. Keeping them in mind through education and conversation can help veterinarians balance their responsibilities as providers of treatment to pets in their care, including provision of antimicrobial drugs when indicated, with their responsibilities as public health guardians.⁸

Clinical Bottom Line

The implications of AMR for companion animal veterinarians, their patients, and clients can be severe, including increased morbidity and mortality, longer illnesses, and increased costs.¹ For veterinarians, there is a threat of restrictions and regulations around the types of antimicrobial drugs available and/or the requirement for approval to use certain drugs in our patients. For all involved, the growing threat of zoonotic spread of AMR is real and must be addressed proactively. Discussions of both the short-term and long-term implications of antimicrobial resistance in support of judicious use of antimicrobial drugs is a crucial behavior change for companion animal veterinarians to take to proactively address this growing issue.

Molly McAllister, DVM, MPH, is the Director of Research for the Banfield Applied Research and Knowledge (BARK) team at Banfield Pet Hospital. She is a graduate of Oregon State University College of Veterinary Medicine and subsequently earned her master of public health degree from the University of Minnesota. Dr. McAllister is passionate about the role of preventive and proactive care in the health and quality of life of our pets, as well as the intersection of human, animal, and environmental health. She lives with her family and 4 pets in Vancouver, Washington, where they spend as much time outdoors as possible.