Abstract
There is an urgent need to develop novel methods for assessing the response of bacteria to antibiotics in a timely manner. Antibiotics are traditionally assessed via their effect on bacteria in a culture medium, which takes 24-48 h and exploits only a single parameter, i.e. growth. Here, we present a multiparameter approach at the single-cell level that takes approximately an hour from spiking the culture to correctly classify susceptible and resistant strains. By hydrodynamically trapping hundreds of bacteria, we simultaneously monitor the evolution of motility and morphology of individual bacteria upon drug administration. We show how this combined detection method provides insights into the activity of antimicrobials at the onset of their action which single parameter and traditional tests cannot offer. Our observations complement the current growth-based methods and highlight the need for future antimicrobial susceptibility tests to take multiple parameters into account.
Highlights
Since the majority of antimicrobial susceptibility tests (ASTs) measures susceptibility of large bacterial populations, they average over billions of organisms
We have identified three signatures of the bacterial response to such challenges: the fraction of bacterial population entering the traps, the amplitude of the movement of each bacterium within the trap, and the bacterial morphology. We demonstrate that these signatures, which are dependent on both motility and morphology, can be used to successfully classify resistant and susceptible strains of E. coli to different antibiotics in about an hour from spiking the culture
A preliminary set of experiments is conducted as a control to prove the ability of the assay to discern motility at the single bacteria level
Summary
Since the majority of ASTs measures susceptibility of large bacterial populations, they average over billions of organisms. One of the first platforms proposed for single bacteria trapping and analysis is the so-called mother machine.[11] Here, a single bacterium (the pole mother cell) is localised in a narrow dead-end microfluidic channel which constricts growth along a single direction in order to follow multiple generations. This configuration is advantageous for studying cell aging and proliferation over extended periods of time.[12,13,14] the accumulation of secreted products and the increased shear along the channel might affect bacteria phenotype and division
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