Abstract
Measuring alterations in bacteria upon antibiotic application is important for basic studies in microbiology, drug discovery, clinical diagnosis, and disease treatment. However, imaging and 3D time-lapse response analysis of individual bacteria upon antibiotic application remain largely unexplored mainly due to limitations in imaging techniques. Here, we present a method to systematically investigate the alterations in individual bacteria in 3D and quantitatively analyze the effects of antibiotics. Using optical diffraction tomography, in-situ responses of Escherichia coli and Bacillus subtilis to various concentrations of ampicillin were investigated in a label-free and quantitative manner. The presented method reconstructs the dynamic changes in the 3D refractive-index distributions of living bacteria in response to antibiotics at sub-micrometer spatial resolution.
Highlights
Understanding how antibiotics induce bacterial cell death is essential in the study of microbiology and to general healthcare in order to help develop, improve, and apply treatment to patients [1]
We demonstrate the capability of optical diffraction tomography (ODT) for imaging the antibiotic response of bacteria in 3D by investigating the response of Escherichia coli and Bacillus subtilis to a β-lactam antibiotic agent, ampicillin
2.1 Optical diffraction tomography To measure the 3D refractive index (RI) tomogram of individual bacteria, we employed optical diffraction tomography based on a Mach-Zehnder interferometer equipped with a digital micromirror device (DMD) [Fig. 1(a)]
Summary
Understanding how antibiotics induce bacterial cell death is essential in the study of microbiology and to general healthcare in order to help develop, improve, and apply treatment to patients [1]. The phenotypic response of bacteria to β-lactam antibiotics has been studied [12, 13], detailed phenotypic aspects have been less explored with little available research on the changes in physical quantities such as cell mass, density, and volume. These parameters are direct indicators of cell survival and growth [14, 15], which can provide fundamental insights into the physical and chemical mechanism of bacterial response to antibiotics. With its non-invasive, label-free, and quantitative analysis, our method provides a useful tool for studying and developing antibiotic agents against clinical pathogens that threaten public health
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