Geometric and optical characteristics of five microorganisms for rapid detection using image processing

A rapid and cost-effective technique for identification and classification of microorganisms was explored using fluorescence microscopy and image analysis. After staining the microorganisms with fluorescent dyes (diamidino-2-phenyl-indole (DAPI) and Acridine Orange (AO)), images of the microorganisms were captured using a CCD camera attached to a light microscope. Optical parameters were extracted from the grey-level histogram of the images. Geometric parameters were similar for the images obtained using two dyes, but optical parameters were different. Six geometric parameters (width, length, area, perimeter, aspect ratio and roundness) obtained can differentiate some microorganisms as various parameters provide different geometrical aspects. Fluorescence emission from Bacillus thuringiensis is the highest compared to other microbes, and the emission from Lactobacillus brevis is the lowest. Mean 10 percentiles of image histograms of Listeria innocua and Staphylococcus epidermidis are significantly different from that of L. brevis. Using 99 percentile, B. thuringiensis can be differentiated from the remaining microbes, and Escherichia coli can also be differentiated from L. brevis and S. epidermidis.