TDLAS-based antimicrobial susceptibility testing using microbial CO2 evolution and validation in Gram-positive and...

Area of Science:

• Microbiology
• Analytical Chemistry
• Spectroscopy

Background:

• Antimicrobial susceptibility testing (AST) is crucial for effective treatment and combating antimicrobial resistance (AMR).
• Traditional AST methods are time-consuming and lack real-time microbial growth data.
• A need exists for rapid, non-invasive, and cost-effective AST solutions.

Purpose of the Study:

• To develop and validate a universal, non-invasive AST method utilizing Tunable Diode Laser Absorption Spectroscopy (TDLAS).
• To quantitatively determine minimum inhibitory concentrations (MICs) by monitoring microbial CO2 evolution.
• To assess the method's stability, accuracy, and applicability to diverse bacterial strains.

Main Methods:

• Monitoring CO2 production in sealed culture bottles via TDLAS.
• Establishing a calibration curve correlating threshold time (TT) with total viable count (TVC).
• Developing a dose-response model for MIC determination and validating against CLSI standards.

Main Results:

• The TDLAS method yielded ampicillin MIC values for *Staphylococcus sciuri* concordant with standard broth microdilution.
• Excellent method stability was demonstrated with a coefficient of variation (CV) of 2.75% over four replicates.
• Successful application to clinical isolates (*Staphylococcus aureus*, *Escherichia coli*, *Enterobacter cloacae*) confirmed broad applicability.

Conclusions:

• The TDLAS-based AST is a universal, non-invasive, and low-cost method yielding accurate MICs.
• It offers superior insights into bacterial growth dynamics under antibiotic stress compared to traditional methods.
• The technology holds significant promise for clinical diagnostics and resource-limited settings.