We developed a direct and rapid method for the diagnosis of death by
drowning by PCR amplification of phytoplankton
DNA using human tissues. The primers were designed based on the DNA sequence of the
16S ribosomal RNA gene (16S
rDNA) of Cyanobacterium. Samples of lung, liver and kidney tissues were collected from 53 autopsied individuals diagnosed as death by
drowning. Without
DNA extraction, the tissue fragments were incubated directly in a digest
buffer developed in this study, for 20 min. Using 1 microL of the tissue digest
solution in PCR, the 16S
rDNA was successfully amplified. The specific 16S
rDNA fragment was identified from the standard picoplankton Euglena gracilis, the tissues of bodies died from
drowning and water samples from the
drowning scenes. On the other hand, no PCR products were found in the tissues of individuals who died from causes other than
drowning. Various quantities of tissue weighing 1, 5, 10, 20 and 30 mg were tested, and the PCR amplification detected the specific 16S
rDNA fragment from all the quantities of tissue tested. This method was found to be more reliable, sensitive, specific and rapid when compared to the conventional diagnosis of death by
drowning using the diatom test by
acid digestion method.