Laser speckle imaging techniques have become widespread in many areas where non-invasive remote measurements are needed. For example, medical and microbiological fields. This technique is applicable for monitoring the behavioral activity of microorganisms. In the current study, using experiments with fungi and bacteria, we compare signal and image processing algorithms for analyzing microorganism’s activity by laser speckle imaging techniques and demonstrate the advantages of the proposed method: sensitive sub-pixel correlation algorithm. The obtained results could allow to propose a technology for faster detection of bacterial and fungal growth in the culture medium. They could also be used to speed up the determination of antibacterial and antifungal susceptibility results.
Our previous studies have shown that laser speckle imaging with sensitive subpixel correlation analysis is able to detect bacterial growth activity and the pattern of colony growth. In the current study, we demonstrate the potential of this method to analyze fungal growth. We compare the characteristics of the signals obtained from bacteria and fungi. The obtained results will help to improve the parameters of the speckle image acquisition system and the signal processing algorithms useful for microorganism (both eukaryotic and prokaryotic) growth analyses and speeding up and facilitating microbiological diagnostics.
The laser speckle imaging technique with sub-pixel correlation analysis allows to identify changes in the sterile zone radius, and makes it possible to predict these changes significantly earlier than the disk diffusion method which is recommended by the European Committee on Antimicrobial susceptibility testing (EUCAST). Results are oriented towards speeding and facilitating epidemiological analysis.
Our previous studies have shown that it is possible to determine the growth activity of a microbial colony by laser speckle imaging techniques. A sub-pixel correlation method was proposed to detect small changes in the sequence of laser speckle images. In this study, we compared the laser speckle imaging method to the reference method - image time series under white light to detect the colony growth parameters (growth rate, critical detection time).
The laser speckle subpixel correlation method was proposed to investigate bacterial activity moving from center to the colony edges. Results could facilitate epidemiological analysis and improve mathematical models of colony growth.
The study aims at development and laboratory approbation of non-contact optical technique for early evaluation of microbial activity. Microorganisms’ activity is estimated by laser speckle contrast imaging technique in combination with image processing of obtained time varying speckle patterns. Laser speckle patterns were captured by CMOS sensor during illumination of growing bacteria colonies by low power (<30 mW, 635 nm) stabilized coherent light source. To validate proposed technique and image processing algorithm the vibrio natriegens bacteria are used. After analysis of several different experiments the following results were obtained: In the central part of the colony activity can be seen in 2.5-3 hours. Thus, earlier detection of bacterial activity is expected, i.e., earlier than 2-3 hours, which is much earlier than the standard counting methods used to count colony forming units (CFU).
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