We have developed a sensitive and specific PCR method for detecting plankton
DNA in cases of death by
drowning. However, this PCR method could not be used for cases of
drowning in water containing no plankton. Bacteria species are normally localized in the throat and trachea and they may invade into blood through the respiratory tract in people who have drowned as well as species localized in water. The aim of this study was to establish a novel and expedient PCR method for detecting bacterial genes in samples from
drowning cases. We designed primer pairs for Streptococcus salivarius (SL1) and Streptococcus sanguinis (SN1), which are common species in the throat, and for Aeromonas hydrophila (AH1), which has been found in various water samples. With SL1, SN1, and AH1, we detected 10, 0.1, and 1 pg of target
DNA, respectively. Among 19 drowned cases within 3 days postmortem, SL-
DNA was detected in all of the blood samples from hearts with SL1 and AH-
DNA was detected in several samples with AH1. In a case of
drowning in a bathtub, use of the conventional
acid digestion method for diatom analyses and the PCR method for identifying plankton
DNA revealed no plankton, but our PCR method for detecting
bacterial DNA showed a positive result for SL-
DNA in a blood sample from the heart. In conclusion, our novel PCR method is highly specific and sensitive for detecting
bacterial DNA and is useful for cases of death by
drowning in water containing no plankton.