Understanding Susceptibility Test Data as a Component of Antimicrobial Stewardship in Veterinary Settings
|Publication Date:||1 July 2019|
This report is designed to facilitate common understanding among veterinarians, microbiologists, and laboratorians about how antimicrobial susceptibility testing (AST) is performed, and how the results can be interpreted and applied to clinical decision-making. The intended audience includes veterinarians, microbiologists, laboratorians conducting in vitro testing, veterinary educators, pharmacists, and students.
To provide this information, the report includes an overview of pharmacological principles relevant to antimicrobial agent selection, some general principles about differences among animal species that may affect antimicrobial agent use and efficacy, and how bacterial species affects AST results and interpretations. This information also helps to explain how microbiological and pharmacological data are used to develop breakpoints. Example AST reports are included, in which common questions are answered and misconceptions are clarified. A large portion of this report provides animal species-specific guidance on applying AST results; reasonable extrapolations that can be made across bacterial species, infection sites, or antimicrobial agents; and the expected degree of confidence in these extrapolations. Also included are excerpts from other CLSI documents relevant to interpreting AST reports.
Based on available expertise and perceived need, this report covers the following animal species: dogs, cats, horses, cattle, pigs, and fish. These animal species represent all the veterinary breakpoints that have been approved to date by the CLSI Subcommittee on Veterinary Antimicrobial Susceptibility Testing (VAST), with the exception of poultry breakpoints for one antimicrobial agent. Interpreting AST results for chicken and turkey pathogens is not discussed in this report, although these animal species are a significant focus for antimicrobial stewardship efforts worldwide. Poultry veterinarians and laboratories handling poultry diagnostics are encouraged to consult CLSI documents VET013 and VET084 for AST guidance.
Clinical decision-making about antimicrobial agents is complicated, and AST data only account for part of the information needed to successfully manage bacterial disease in animals. This report does not include any guidance on how to diagnose or treat bacterial disease in animals, prescribing information, or dosing recommendations. Dosage regimens used to set breakpoints are included only to aid in interpreting AST results. This report is not intended to produce standards for antimicrobial prescribing, to affect or supersede current regulatory restrictions on antimicrobial agent use, or to endorse any particular product for antimicrobial use. Additional factors veterinarians consider when making final decisions on prescribing antimicrobial agents include disease factors (eg, severity and duration), patient factors (eg, potential for adverse effects or selection for antimicrobial resistance), and legal restrictions on drug use, as well as their own experience; however, these factors are not discussed in depth in this report.
3 CLSI. Performance Standards for Antimicrobial Disk and Dilution Susceptibility Tests for Bacteria Isolated From Animals. 5th ed. CLSI standard VET01. Wayne, PA: Clinical and Laboratory Standards Institute; 2018.
4 CLSI. Performance Standards for Antimicrobial Disk and Dilution Susceptibility Tests for Bacteria Isolated From Animals. 4th ed. CLSI supplement VET08. Wayne, PA: Clinical and Laboratory Standards Institute; 2018.