Laser speckle imaging for early detection of microbial colony forming units

Abstract

In this study, an optical contactless laser speckle imaging technique for the early identification of bacterial colony-forming units was tested. The aim of this work is to compare the laser speckle imaging method for the early assessment of microbial activity with standard visual inspection under white light illumination. In presented research, the growth of Vibrio natriegens bacterial colonies on the solid medium was observed and analyzed. Both – visual examination under white light illumination and laser speckle correlation analysis were performed. Based on various experiments and comparisons with the theoretical Gompertz model, colony radius growth curves were obtained. It was shown that the Gompertz model can be used to describe both types of analysis. A comparison of the two methods shows that laser speckle contrast imaging, combined with signal processing, can detect colony growth earlier than standard CFU counting method under white light illumination.

Plasmonic optical fiber for bacteria manipulation—characterization and visualization of accumulation behavior under plasmo-thermal trapping

“…for studies of colony growth, antibacterial susceptibility, etc.) [ 57 – 62 ]. Furthermore, our approach uses the white light images taken using a general optical microscope unlike the abovementioned examples (which all require laser illumination), thereby offering greater versatility and potential for wider applications.…”

Use of the speckle imaging sub-pixel correlation analysis in revealing a mechanism of microbial colony growth

“…In the previous studies, the authors described sensitive correlation subpixel analysis, which can help detect bacterial activity and its effects within a colony 8,12 . The entire field of the experiment (Petri dish) was divided into small sections of NxN pixels.…”

“…where ω is the width of the active cell proliferation zone of the colony, r is the colony radius at time t, and 𝑟 0 is the radius at t = 0; α is the specific growth rate also known as (μ, h -1 ), which can be found from the Gompertz equation 8,17 . Thus, having the experimental data (the radius of the colony growth, the corresponding time, and μ), it is possible to calculate the width of the active zone or the width of the "ring" using Eq.…”

Laser Applications for Estimation of Microbial Activity and Investigation of NIR Skin Autofluorescence

“…The frequency domain of the observed signal is up to 16.7 mHz. According to our previous research described in paper [12,13] "signal" (or time signal) represents the result of the correlation and interpolation algorithm between each pair of consecutive speckle image frames. Further, the scatter of the specific growth rate µ!, with the average experimental value of 0.17 h -1 (Fig.…”