MICy: a Novel Flow Cytometric Method for Rapid Determination of Minimal Inhibitory Concentration

Area of Science:

• Microbiology
• Clinical Diagnostics
• Flow Cytometry Applications

Background:

• Early and adequate antibiotic treatment is critical in intensive care settings.
• Current antibiotic susceptibility testing (AST) methods can be time-consuming, delaying crucial clinical decisions.
• Accelerating AST can lead to improved patient outcomes and reduced healthcare costs.

Purpose of the Study:

• To develop a simple, rapid flow cytometry (FC)-based AST protocol (MICy) for reliable results within hours.
• To evaluate the accuracy and efficiency of the MICy method compared to standard microdilution techniques.

Main Methods:

• Developed a flow cytometry (FC)-based AST protocol (MICy).
• Tested MICy on six bacterial strains (e.g., E. coli, P. aeruginosa, S. aureus) against 12 antibiotics.
• Compared MICy results with standard microdilution, including statistical analysis (McNemar, Fleiss' kappa) and breakpoint evaluation (EUCAST).

Main Results:

• FC detected bacterial growth within 4 hours, enabling rapid AST.
• MICy demonstrated high agreement with microdilution: >87% exact match and >80% agreement within ±1 dilution.
• Susceptibility profiles generated by MICy matched microdilution in >92% of cases, with low discrepancy rates (8.7% major, 3.2% very major).

Conclusions:

• MICy is a novel, simple, and rapid FC-based AST method.
• MICy provides reliable antibiotic susceptibility profiles a workday earlier than traditional methods.
• This accelerated testing facilitates timely clinical decision-making, potentially improving patient outcomes and reducing antibiotic resistance.