Early detection of bacteria in the lag phase using the distribution of relaxation times analysis

Abstract

Impedance spectroscopy has been explored for bacterial detection due to its rapid and noninvasive detection. In a bacterial solution, various components, including the culture medium, bacterial cells, and metabolites from bacterial growth, are present, and they exhibit different responses to alternating current electric fields depending on their size and charge. However, conventional impedance spectroscopy for bacterial detection typically considers only overall polarization processes, as isolating individual processes can be challenging. Here, we report on the distribution of relaxation times (DRTs) method, which enables the separation of polarization processes occurring at different time scales. By calculating DRTs from impedance spectra measured during bacterial growth or death, we successfully differentiated between the lag and exponential phases of growth in Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa. This demonstrates its potential for early bacterial detection during the lag phase. In addition, DRT analysis allowed us to distinguish between the mechanisms of action of the antibiotics meropenem and tetracycline.