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Microscopic observation of live parasites in the stool is an important diagnostic tool in human and veterinary medicine. Because of the presence of large amounts of contaminating organic matter, microscopic analysis must be preceded by time-consuming pre-purification steps. Transmission-through-dye (TTD) optical microscopy obviates this problem. The purpose of this study is to illustrate the use of TTD for the analysis of stool samples.TTD imaging is based on the exclusion of a strongly absorbing dye by living cells. A food colorant Acid Blue 9 (AB9) is added to a fecal suspension, and the sample is observed under transmitted illumination through a 630 nm bandpass filter. AB9 strongly absorbs red light, and it comes out of the sample significantly attenuated. However, if a viable cell of any origin is present in the sample, it excludes the dye and reduces the depth of the light-absorbing layer.Live cells or eggs appear bright red on a dark background, while most of the organic contaminants remain dark. The method has been demonstrated on schistosomes, hookworms, giardia, yeast, and other organisms.TTD dramatically increases the visibility of live parasites and permits their direct observation in a fecal suspension. TTD can be enabled on any microscope by simply adding a red filter. |
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