Antimicrobial susceptibility testing: An updated primer for clinicians in the era of antimicrobial resistance: Insights from the Society of Infectious Diseases Pharmacists

Abstract

Antimicrobial susceptibility testing (AST) is a critical function of the clinical microbiology laboratory and is essential for optimizing care of patients with infectious diseases, monitoring antimicrobial resistance (AMR) trends, and informing public health initiatives. Several methods are available for performing AST including broth microdilution, agar dilution, and disk diffusion. Technological advances such as the development of commercial automated susceptibility testing platforms and the advent of rapid diagnostic tests have improved the rapidity, robustness, and clinical application of AST. Numerous accrediting and regulatory agencies are involved in the process of AST and setting and revising breakpoints, including the U.S. Food and Drug Administration and the Clinical and Laboratory Standards Institute. Challenges to optimizing AST include the emergence of new resistance mechanisms, the development of new antimicrobial agents, and generation of new data requiring updates and revisions to established methods and breakpoints. Together, the challenges in AST methods and their interpretation create important opportunities for well-informed clinicians to improve patient outcomes and provide value to antimicrobial stewardship programs, especially in the setting of rapidly changing and increasing AMR. Addressing AST challenges will involve continued development of new technologies along with collaboration between clinicians and the laboratory to facilitate optimal antimicrobial use, combat the increasing burden of AMR, and inform the development of novel antimicrobials. This updated primer serves to reinforce important principles of AST, and to provide guidance on their implementation and optimization.

Elucidating effects of single and multiple resistance mechanisms on bacterial response to meropenem by quantitative and systems pharmacology modeling and population genomics

“…Thus, many patients are still being treated empirically, which often leads to poor outcomes and increased resistance (55,56). Currently, with the increasing burden of antimicrobial resistance, rapid WGS-based diagnostic testing is an option that could allow for identification of the infecting pathogen including detection of resistance genes (57).…”

“…Standard, culture-dependent antimicrobial susceptibility testing is labour-intensive and often requires several days, which may delay selection of appropriate therapy (53, 54). Thus, many patients are still being treated empirically, which often leads to poor outcomes and increased resistance (55, 56). Currently, with the increasing burden of antimicrobial resistance, rapid WGS-based diagnostic testing is an option that could allow for identification of the infecting pathogen including detection of resistance genes (57).…”

From bottle to bedside: Implementation considerations and antimicrobial stewardship considerations for bloodstream infection rapid diagnostic testing

“…Standards Institute (CLSI) direct from blood culture disk diffusion methods. 77 Additionally, interpretative criteria are currently only valid for a limited number of organisms and antibiotic agents. Several platforms are in development for rapid, direct from positive blood culture, phenotypic testing that uses novel methodologies.…”

“…Excluding the Accelerate PhenoTest BC®, current mRDTs available in the United States do not provide phenotypic methods for rapid antibiotic susceptibilities from blood cultures 76 . Certain rapid methods for phenotypic data tend to be labor intensive with limited validated antibiotic agents, such as Clinical and Laboratory Standards Institute (CLSI) direct from blood culture disk diffusion methods 77 . Additionally, interpretative criteria are currently only valid for a limited number of organisms and antibiotic agents.…”

Predicting S. aureus antimicrobial resistance with interpretable genomic space maps

“…To establish a diagnosis and prescribe proper treatment for patients with bacterial infection, clinicians usually rely on in vitro antimicrobial susceptibility testing (AST) [3]. AST is considered to be a 'golden standard' for choosing optimal antibiotics to which the pathogen in question is susceptible [4].…”