High-throughput quantification of population dynamics using luminescence

Area of Science:

• Microbiology
• Antimicrobial Resistance
• Bacterial Physiology

Background:

• Bacterial population decline above minimum inhibitory concentrations (MIC) is poorly understood.
• Standard colony-forming units (CFU) assays are slow and labor-intensive.
• Luminescence assays are efficient but their reliability at high antibiotic concentrations is unclear.

Purpose of the Study:

• Compare luminescence and CFU-based methods for quantifying bacterial decline at super-MIC concentrations.
• Identify factors influencing discrepancies between luminescence and CFU measurements.
• Assess luminescence as a high-throughput alternative for bacterial dynamics studies.

Main Methods:

• Cultured *Escherichia coli* and exposed it to 20 different antimicrobials at super-MIC concentrations.
• Quantified bacterial decline using both luminescence assays and colony-forming unit (CFU) counts.
• Analyzed differences in decline rates and investigated underlying physiological reasons.

Main Results:

• Luminescence and CFU-based bacterial decline rates agreed for half of the antimicrobials tested.
• CFU-based decline rates were consistently higher for the other half.
• Discrepancies arose from bacterial filamentation (luminescence tracks biomass) and reduced colony formation (CFU reflects culturability).

Conclusions:

• Luminescence assays can be a viable, high-throughput alternative to CFU for quantifying bacterial decline at super-MIC concentrations.
• The suitability of luminescence depends on the antimicrobial's specific physiological effects.
• Distinguish between cell number and biomass when interpreting luminescence data for bacterial dynamics.