Rapid Susceptibility Testing Methods

Abstract

With emerging antimicrobial resistance, rapid antimicrobial susceptibility testing (AST) is needed to provide early definitive therapeutic guidance to optimize patient outcome. Genotypic methods are fast, but can identify only a subset of known resistance elements. Phenotypic methods determine clinically predictive minimal inhibitory concentrations and include very sensitive optical and biophysical methods to detect changes in replication or physiology of pathogens in response to antibiotics. For the potential of rapid AST to be fully realized, results must be linked with robust decision support solutions that will implement therapeutic changes in real time.

Keywords: Antimicrobial resistance; Genotypic; Phenotypic; Rapid antimicrobial susceptibility testing.

Figure 1.. Reducing the antimicrobial testing gap.

Rapid AST will reduce the time between the start of empiric therapy and definitive therapy based on AST data by at least one day for methods that test isolated bacterial growth and by at least two days for methods that test primary specimens directly. Rapid AST data will allow life-saving therapeutic corrections, and tailoring of therapy to foster stewardship goals and avoid complications from extended broad-spectrum empiric therapy.

Figure 2.. Loss of reliable empiric therapy.

Over the next two decades, antimicrobial resistance will increase significantly. The number of available antimicrobials will also increase, but not at the same pace. As a result, the likelihood that any given empiric therapy will be effective will decrease. Therefore, rapid AST will become increasingly necessary to ensure patients are on active therapy in time to make a difference.

Figure 3.. AST-ASSIST.

Rapid AST is only truly rapid if results can be acted upon quickly. To this end, we envision a decision support system, AST-ASSIST, that will leverage use of provider other pathways (POPs), which contain instructions for initial empiric antibiotics and options for reflexed directed antimicrobial therapy populated based on patient medical and microbiological history and local antibiogram. AST-ASSIST will implement therapeutic changes included within the POP based on organism identity and rapid AST results through interface with pharmacy and nursing systems and/or notify clinicians through pager or text message for additional timely input as needed.