Rapid Phenotypic Antimicrobial Susceptibility Testing Using a Coulter Counter and Proliferation Rate Discrepancy

Area of Science:

• Clinical microbiology
• Antimicrobial resistance
• Diagnostic development

Background:

• Antimicrobial resistance (AMR) necessitates rapid diagnostics for effective treatment.
• Current antimicrobial susceptibility testing methods are time-consuming, delaying clinical decisions.
• Accurate and swift antimicrobial susceptibility determination is crucial for patient outcomes.

Purpose of the Study:

• To develop and validate a rapid phenotypic antimicrobial susceptibility determination method.
• To enable seamless clinical implementation of a novel diagnostic tool.
• To combat antimicrobial resistance through timely and evidence-based prescribing.

Main Methods:

• Development of a Coulter counter-based antimicrobial susceptibility testing (CAST) method.
• Integration of bacterial incubation, population growth monitoring, and automated result analysis.
• Quantitative detection of bacterial growth differences after 2-hour antimicrobial exposure.

Main Results:

• CAST accurately determined antimicrobial susceptibility phenotypes based on distinct bacterial proliferation rates.
• Evaluation on 74 clinical isolates of *Enterobacteriaceae* against 15 antimicrobials.
• Achieved 90.18% absolute categorical agreement compared to the standard 24-hour broth microdilution method.

Conclusions:

• The CAST method provides rapid and accurate phenotypic antimicrobial susceptibility results.
• This 2-hour test facilitates timely clinical decisions for bacterial infections.
• CAST shows significant potential for clinical implementation to combat antimicrobial resistance.