Detection of diatom in formalin-fixed organs by enzymatic digestion

The detection of diatoms has been proposed to be useful in the diagnosis of drowning. Enzymatic digestion of unfixed lungs and other organs is widely used to detect diatoms. In the present study, we examined the application of enzymatic digestion for diatom detection in formalin-fixed organs obtained at autopsy. Furthermore, we assessed the effect of hydrogen peroxide on contamination of the lung specimen with foreign bodies inhaled in the course of drowning or as a result of smoking or air pollution. Unfixed lung was digested with proteinase K for 2d and centrifuged; the supernatant was then removed. On the other hand, formalin-fixed lung samples were boiled in Tris-HCl buffer containing sodium dodecyl sulfate (SDS) and then subjected to enzymatic digestion. A portion of formalin-fixed or unfixed samples digested with proteinase K was incubated with hydrogen peroxide at 80 degrees C and mounted on a slide, while the remaining portion was processed without incubation. Samples incubated with hydrogen peroxide showed clearer image of diatoms than those not incubated with hydrogen peroxide; this is because the inhaled foreign bodies were discolored in the former samples. Therefore, incubation of digested samples with hydrogen peroxide would be helpful for quantitative and qualitative analyses of diatoms.