Responsible antimicrobial use in critically ill adult horses

Due to increasing antimicrobial resistance, pressure on veterinarians is mounting to adhere to responsible use of antimicrobial drugs. Antimicrobials are frequently included in the treatment of systemically ill horses due to the strong likelihood of an infection and the innate difficulties in differentiating systemic inflammation secondary to noninfectious from infectious causes. In light of increasing antimicrobial drug resistance and the potential negative impact of antimicrobials on equine patients, every attempt should be made to identify noninfectious disease, choose first-line antimicrobials and discontinue treatment as soon as possible. In most cases, a short duration of antimicrobial therapy ranging from a single dose (e.g. preoperatively) to 24–72 h might be sufficient with long-term treatment being rarely required. This article aims to provide practical guidelines for antimicrobial drug usage in critically ill adult horses by describing ancillary diagnostic aids that can help establishing whether or not an infection is present, discussing commonly encountered pathogens and their typical antimicrobial drug sensitivity patterns, and providing some guidance how to safely shorten the duration of antimicrobial therapy.     

Antimicrobial drug use in veterinary medicine

Recognizing the importance of antimicrobial resistance and the need for veterinarians to aid in efforts for maintaining the usefulness of antimicrobial drugs in animals and humans, the Board of Regents of the American College of Veterinary Internal Medicine charged a special committee with responsibility for drafting this position statement regarding antimicrobial drug use in veterinary medicine. The Committee believes that veterinarians are obligated to balance the well-being of animals under their care with the protection of other animals and public health. Therefore, if an animal's medical condition can be reasonably expected to improve as a result of treatment with antimicrobial drugs, and the animal is under a veterinarian's care with an appropriate veterinarian-client-patient relationship, veterinarians have an obligation to offer antimicrobial treatment as a therapeutic option. Veterinarians also have an obligation to actively promote disease prevention efforts, to treat as conservatively as possible, and to explain the potential consequences associated with antimicrobial treatment to animal owners and managers, including the possibility of promoting selection of resistant bacteria. However, the consequences of losing usefulness of an antimicrobial drug that is used as a last resort in humans or animals with resistant bacterial infections might be unacceptable from a public or population health perspective. Veterinarians could therefore face the difficult choice of treating animals with a drug that is less likely to be successful, possibly resulting in prolonged or exacerbated morbidity, to protect the good of society. The Committee recommends that voluntary actions be taken by the veterinary profession to promote conservative use of antimicrobial drugs to minimize the potential adverse effects on animal or human health. The veterinary profession must work to educate all veterinarians about issues related to conservative antimicrobial drug use and antimicrobial resistance so that each individual is better able to balance ethical obligations regarding the perceived benefit to their patients versus the perceived risk to public health. Specific means by which the veterinary profession can promote stewardship of this valuable resource are presented and discussed in this document.     

Evaluation of Specific Infection Control Practices Used by Companion Animal Veterinarians in Community Veterinary Practices in Southern Ontario

This study evaluated specific infection control practices in community veterinary practices in southern Ontario. Environmental disinfection, management of infectious patients and antimicrobial use in clean surgical procedures were investigated. Community companion animal veterinary practices (n = 101) in Southern Ontario were recruited, and a questionnaire was administered to one veterinarian and one veterinary technician from each practice. The veterinarian questionnaire gathered data on clinic demographics, management of infectious patients, infectious diseases of concern, environmental disinfection and antimicrobial use in surgical procedures. The veterinary technician questionnaire gathered data on environmental disinfection. None of the veterinary practices had a formal infection control programme. Sixty‐five per cent (n = 66) of the veterinary practices did not have an isolation area and 61% (n = 40) of these practices did not employ any specific infection control measures for infectious cases. The products most frequently used for environmental disinfection were hydrogen peroxide based or quaternary ammonium compounds. Bleach was the agent most commonly used for environmental disinfection of infectious body fluids; however 60% of the veterinarians and 40% of the veterinary technicians did not identify a product for environmental disinfection of infectious body fluids. Twenty‐four per cent of the veterinarians reported using antimicrobials in animals undergoing elective sterilization surgeries and 60% reported using antimicrobials in other clean surgical procedures. There is a need for community veterinary practices to develop infection control programmes specific to their individual practice. In addition, veterinarians should discontinue the common use of antimicrobials for clean elective sterilization surgical procedures.     

Metrics for quantifying antimicrobial use in beef feedlots

Accurate antimicrobial drug use data are needed to enlighten discussions regarding the impact of antimicrobial drug use in agriculture. The primary objective of this study was to investigate the perceived accuracy and clarity of different methods for reporting antimicrobial drug use information collected regarding beef feedlots. Producers, veterinarians, industry representatives, public health officials, and other knowledgeable beef industry leaders were invited to complete a web-based survey. A total of 156 participants in 33 US states, 4 Canadian provinces, and 8 other countries completed the survey. No single metric was considered universally optimal for all use circumstances or for all audiences. To effectively communicate antimicrobial drug use data, evaluation of the target audience is critical to presenting the information. Metrics that are most accurate need to be carefully and repeatedly explained to the audience.     

Antimicrobial labelling in Australia: a threat to antimicrobial stewardship?

Antimicrobial resistance is a public health emergency, placing veterinary antimicrobial use under growing scrutiny. Antimicrobial stewardship, through appropriate use of antimicrobials, is a response to this threat. The need for antimicrobial stewardship in Australian veterinary practices has had limited investigation. A 2016 survey undertaken to investigate antimicrobial usage patterns by Australian veterinarians found that antimicrobial dose rates were varied and often inappropriate. Doses of procaine penicillin in horses and cattle were often low, with 68% and 90% of respondents, respectively, reporting doses that were unlikely to result in plasma concentrations above minimum inhibitory concentrations for common equine and bovine pathogens. Frequency of penicillin administration was also often inappropriate. Gentamicin doses in horses were largely appropriate (89% of dose rates appropriate), but 9% of respondents reported twice daily dosing. Amoxycillin and amoxycillin‐clavulanate were administered at the appropriate doses, or above, to dogs and cats by 54% and 70% of respondents, respectively. Here, we explore the potential reasons for inappropriate antimicrobial dose regimens and report that antimicrobial labels often recommend incorrect dose rates and thus may be contributing to poor prescribing practices. Changes to legislation are needed to ensure that antimicrobial drug labels are regularly updated to reflect the dose needed to effectively and safely treat common veterinary pathogens. This will be especially true if changes in legislation restrict antimicrobial use by veterinarians to the uses and doses specified on the label, thus hampering the current momentum towards improved antimicrobial stewardship.     

Systemic antimicrobial therapy in foals

Antimicrobial agents are commonly used in neonatal foals for the treatment or prevention of sepsis. However, due to concerns about the development of antimicrobial resistance and increasing pressure on veterinarians to rationalise antimicrobial use, we should be trying to reduce the unnecessary use of antimicrobials. This article reviews many of the important considerations when selecting an antimicrobial for use in neonatal foals. Firstly, we consider general differences in neonatal pharmacology and physiology. Secondly, we review common antimicrobial drugs and their indications. Finally, we review antimicrobial stewardship.     

Antimicrobial selection, administration and dosage

Various types of information contribute to the selection of an antimicrobial agent. Initial requirements are diagnosis of the site and nature of the infection, assessment of the severity of the infectious process and medical condition of the diseased animal; these are embodied in clinical experience. Additional considerations include identification of the causative pathogenic microorganism, knowledge of its susceptibility to antimicrobial agents (microbiological considerations) and of the pharmacokinetic properties of the drug of choice and alternative drugs, and their potential toxicity (pharmacological considerations) in the animal species. Select an antimicrobial drug and dosage form appropriate for use in the particular animal species. Usual dosage regimens may be applied, except in the presence of renal or hepatic impairment, when either modified dosage or a drug belonging to another class should be used. The duration of therapy is determined by monitoring the response both by clinical assessment and bacterial culture. A favourable clinical response is the ultimate criterion of successful therapy.     

Dosing equine antimicrobials: Ensuring clinical success and avoiding antimicrobial resistance

Underdosing of equine antimicrobials is a global issue and may be contributing to antimicrobial resistance in horses. Recent research in Australia has identified that most antimicrobial use in peer-reviewed literature is at a higher dose than that currently on the label for many common equine antimicrobials in the United States, the UK and Australia. These dosing regimens used are now considered the most appropriate doses to be using in horses and veterinarians treating equine patients should be aware of the contemporary dosing regimens.     

Overview of the use of antimicrobial drugs for the treatment of bacterial infections in horses

The use of antimicrobials in veterinary medicine is under great scrutiny with the emergence of antimicrobial resistance in the human population. Equine veterinarians rely on antimicrobials as an essential tool for the treatment of infections in horses, but there is much criticism of some use, particularly prophylaxis. While the appropriate use of antimicrobials can be justified in equine medicine, the misuse cannot. The definition of appropriate use is complex and involves the indication for therapy, antimicrobial selection, dosing regimen and timing and route of administration, duration of therapy and modification of therapy based on microbial susceptibility and clinical response. The aim of this article is to provide guidance on these factors to assist equine veterinarians in determining what constitutes appropriate antimicrobial use in horses.     

Stakeholder position paper: companion animal veterinarian

The total quantity of use in companion animals is generally believed to be relatively small in comparison with antimicrobial use in food animals. Use in companion animals is principally for treatment, whereas the greater proportion of use in food animals is for prophylaxis, metaphylaxis and growth promotion. Therefore, it is important to collect data on end use in companion animals so that overall estimates of use in companion animals can be generated and separated from estimates for food animals. However, data from antimicrobial use in companion animals are extremely limited and no serious attempts to collect such data have ever been made in the United States. The lack of usage data in is concomitant with the dearth of information on antimicrobial resistance in companion animals. Companion animals have been involved in the transmission to humans of, or become infected with, foodborne zoonotic bacteria such as Salmonella and Campylobacter. Companion animals are an integral part of the ecology of antimicrobial resistance through their contact with food animals and exposure to antimicrobials for disease treatment and through contact with humans and the environment. In the practice of companion animal medicine, antimicrobial use data are important for understanding the potential impact on companion animal heath posed by antimicrobial resistance transferred from food animals, humans and the environment, and the threat to humans and other companion animals posed by antimicrobial use in companion animals. Basic information on the patterns and quantities of antimicrobial use in combination with resistance surveillance data, could help companion animal veterinarians understand the potential for development, or evidence of, an antimicrobial resistance problem in their practices, the role of companion animals in the overall epidemiology of antimicrobial resistance, and for comparison with local, regional, or national data. The combination of data from either a sentinel site system of clinics or a use survey with national data from the pharmaceutical industry should provide sufficient data to credibly estimate the total volume and patterns of antimicrobial use in companion animal medicine. The time and effort for use monitoring or to complete a survey would likely become burdensome. Practice management software now utilized at most companion animal clinics could be used to generate antimicrobial use data as well as patient population data as surrogate for the true population at risk for patient encounters in a companion animal practice.     

Antimicrobic susceptibility of bacterial pathogens from horses

Rational choice of an antimicrobial agent requires that the condition for which the drug is prescribed contain an infectious agent and, if so, knowledge of the susceptibility of the microorganism to antimicrobial drugs. Unfortunately, most infectious conditions necessitate the use of an antimicrobic drug before data from the microbiology laboratory are available. The data presented are meant to serve as a guide in the choice of antimicrobic drugs for treatment of infectious processes of the horse before knowledge of the nature of the microorganism isolated as well as its susceptibility to antimicrobic agents. What has been presented are the most commonly isolated microorganisms together with their susceptibility to antimicrobic drugs.     

Developing an open-access antimicrobial resistance learning site for veterinary medical students

Recognizing the crucial role of veterinarians in mitigating antimicrobial resistance (AMR), the Centers for Disease Control and Prevention (CDC) has funded the development of a suite of educational materials to promote the responsible veterinary medical use of antimicrobials. An open-access, Web-based multimedia curriculum regarding antimicrobial resistance in veterinary practice was thus created. The antimicrobial-resistance learning site (AMRLS) for veterinary medical students was completed and made available for use in January 2011 (http://amrls.cvm.msu.edu/). Designed for integration into existing veterinary medical courses, the AMRLS is also a resource for continuing education for practicing veterinarians, animal scientists, and food-animal industry specialists. This Web site emphasizes the mechanisms by which AMR emerges and spreads, the significant role of veterinarians in mitigating AMR, and the need to preserve the efficacy of antibiotics for future generations.     

Antimicrobial use Guidelines for Treatment of Respiratory Tract Disease in Dogs and Cats: Antimicrobial Guidelines Working Group of the International Society for Companion Animal Infectious Diseases

Respiratory tract disease can be associated with primary or secondary bacterial infections in dogs and cats and is a common reason for use and potential misuse, improper use, and overuse of antimicrobials. There is a lack of comprehensive treatment guidelines such as those that are available for human medicine. Accordingly, the International Society for Companion Animal Infectious Diseases convened a Working Group of clinical microbiologists, pharmacologists, and internists to share experiences, examine scientific data, review clinical trials, and develop these guidelines to assist veterinarians in making antimicrobial treatment choices for use in the management of bacterial respiratory diseases in dogs and cats.     

Predictors of differences in the perception of antimicrobial resistance risk in the treatment of sick, at-risk, and high-risk feedlot cattle

Concerns exist that some uses of antimicrobials in cattle may lead to the emergence, proliferation, dissemination and persistence of resistant pathogenic bacteria in animal agriculture, which in turn can infect humans via the food supply. The degree of perceived risk varies with the clinical indication for which the antimicrobial in question is used. In this study, four uses of antimicrobials are considered, including in acutely sick, chronically sick, at-risk, and high-risk cattle, contrasting the degree of risk among these uses. Using a random sample of 103 feedlot cattle veterinarians and variables drawn from the theory of planned behavior, we predict differences in risk perception by clinical indication with differences in perceived efficacy of antimicrobials, social pressures to use antimicrobials, and moral obligations to use antimicrobials. In most models, veterinarians who perceived that others in the feedlot industry (i.e., other feedlot veterinarians, nutritionists, feedlot clients, and retained owners of cattle) were more likely to expect them to use antimicrobials in one situation versus another, the less likely those veterinarians perceived the risk of antimicrobial risk to be greater in the former versus the latter situation. Only two of these contrasts contained influences outside the immediate feedlot relationships. This exception involves the 'downstream' public: meat packers, retailers, and consumers. Veterinarians who believe that using antimicrobials for acutely sick cattle is more beneficial than using antimicrobials for chronically sick cattle were more likely to believe that antimicrobial resistance was a less probable outcome in acutely sick cattle than in chronically sick cattle.     

Overview of the use of antimicrobials for the treatment of bacterial infections in horses

Use of antimicrobial drugs is central to the treatment of primary and secondary bacterial infection in horses. When selecting an antimicrobial to treat confirmed or suspected bacterial infection multiple factors should be considered, including: the likely infectious agent; distribution and dosage of selected drugs; mechanisms of action; and potential side effects. Many of these issues will be covered in subsequent articles in this series. The aim of this paper is to aid the clinician in the rational selection of antimicrobials by reviewing the mode of action, spectrum of activity, pharmacokinetics, pharmacodynamics, indications and potential side effects of the main classes of antimicrobial drugs. Extralabel use of drugs is common in veterinary medicine due to a lack of licensed products. This increases the importance of a thorough understanding of antimicrobials and their possible adverse effects.     

Treatment rationale for dogs poisoned with aldicarb (carbamate pesticide)

The treatment rationale for dogs poisoned by aldicarb is reviewed from a pharmacological perspective. The illegal use of aldicarb to maliciously poison dogs is a major problem in some parts of the world. In South Africa, it is probably the most common canine poisoning treated by companion animal veterinarians. Aldicarb poisoning is an emergency and veterinarians need to be able to diagnose it and start with effective treatment immediately to ensure a reasonable prognosis. Successful treatment depends on the timely use of an anti-muscarinic drug (e.g. atropine). Additional supportive treatment options, including fluid therapy, diphenhydramine, benzodiazepines and the prevention of further absorption (activated charcoal) should also be considered. Possible complications after treatment are also briefly discussed.     

Prevalence of oxacillin- and multidrug-resistant staphylococci in clinical samples from dogs: 1,772 samples (2001-2005)

OBJECTIVE: To determine whether resistance to oxacillin and other antimicrobials in 3 Staphylococcus spp commonly isolated from dogs increased from 2001 to 2005. DESIGN: Retrospective case series. SAMPLE POPULATION: 1,772 clinical samples of various types obtained from dogs examined at the University of Tennessee Veterinary Teaching Hospital or at regional veterinary hospitals and submitted to the bacteriology and mycology laboratories associated with the teaching hospital. PROCEDURES: Samples were submitted by attending veterinarians to the bacteriology and mycology laboratories for routine aerobic microbial culture. Identification and antimicrobial susceptibility procedures were performed on all isolates. Susceptibility reports for each antimicrobial and Staphylococcus spp were determined from aggregate electronically archived test results. Oxacillin and multidrug resistance for Staphylococcus intermedius was analyzed by reviewing disk diffusion zone measurements. RESULTS: Oxacillin resistance increased among S. intermedius isolates during the past 5 years, and the increase was associated with multidrug resistance. In 2005, 1 in 5 Staphylococcus spp isolates from canine clinical samples was resistant to oxacillin. The most common staphylococcal species isolated were S. intermedius (n = 37), Staphylococcus schleiferi (21), and Staphylococcus aureus (4), and frequencies of oxacillin resistance in isolates of these species were 15.6%, 46.6%, and 23.5%, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Veterinarians should be aware of the potential for empiric drug treatment failures in instances where Staphylococcus spp infections are common (eg, pyoderma). Judicious use of bacterial culture and susceptibility testing is recommended.     

Improving clinical outcomes via responsible antimicrobial use in horses

The growing problem of antimicrobial resistance affects veterinarians on a daily basis. Antimicrobial stewardship and responsible prescribing are essential for a future with effective antimicrobials, as it is unlikely that new antimicrobials will become available for use in horses in the near future. Extended-spectrum β-lactamase (ESBL) producing Enterobacteriaceae, methicillin-resistant Staphylococcus aureus (MRSA) and Salmonella spp. are pathogens of significant concern but there are also other opportunistic pathogens such as Pseudomonas spp., α-haemolytic Streptococcus spp., Enterococcus spp. and Acinetobacter spp. which, due to their high intrinsic resistance, have limited treatment options in adult horses. It is essential that highest priority critically important antimicrobials such as ceftiofur, enrofloxacin, rifampicin and polymyxin B are used prudently in horses and ideally based on culture and antimicrobial susceptibility testing (AST). For example, the use of polymyxin B at a low anti-endotoxic dose rather than at a higher antimicrobial dose in horses for the treatment of systemic inflammatory response syndrome is a potential driver for resistance to colistin (polymyxin E), an antimicrobial used as a last resort in the treatment of multidrug resistant (MDR) Enterobacteriaceae infections in humans. Serum procalcitonin levels are used in humans to distinguish noninfectious inflammatory conditions from inflammation caused by bacteria and other infectious agents and are also used to guide cessation of antimicrobial treatment. Although no such studies have been performed in horses, this or other markers may prove to be helpful in guiding antimicrobial treatment decisions in the future. Optimising sampling techniques and good communication with the microbiology laboratory are essential for generating the accurate culture and AST results that underpin appropriate antimicrobial use. Additionally, there is clearly a need for national and international harmonisation of laboratory methods in order to improve the reliability and consistency of results reported by different laboratories.