A study on detection of rbcL gene for diatoms involved in drowning

Abstract:

Objective：To establish the PCR method with capillary electrophoresis（PCR-CE） for the detection of rbcL gene of diatoms involved in drowning based on the specific primers for diatoms rbcL gene. Methods：With 29 microbes probably involved with drown－ing，a PCR-CE detection system with the primer for diatom rbcL gene labelled with fluorescent was established to verify the specificity and stability. The effectiveness of the PCR-CE method for the diatoms rbcL gene detection in corpses samples was evaluated by com－paring the results of MD-VF-Auto SEM. Results：Positive results（size=197 bp） were achieved with 6 diatoms species（Navicula sp.，Nitzschia sp.，Cyclotella sp.，Melosira varians，Synedra radians，Skeletonema） by the PCR-CE method，by contrast with negative out－comes for other species. The sensitivity of the above 6 species of diatoms DNA were 0.502，0.117，0.029，0.042，0.275，0.215 ng，respectively（20 μL PCR system）. 35 cases of corpses（3 corpses land deaths，2 waterborne corpse cases of non-drowning，30 drown－ing cases） were detected，the detection rate of diatoms in the lungs，liver and kidney of the corpses was 100%，63.3% and 53.3%，respectively. The total positive rate was 83.3%. When the diatom content >10/10 g，the total positive rate was 100% by MD-VF-Auto SEM method. The total positive rate was and 92.6% by PCR-CE，there was no statistical difference（ ?字2=2.077，P=0.491），otherwise，there was statistical difference（P<0.05）. Conclusion：Because of less sample consumption，the PCR-CE method based on the ND-rbcL primer has a good prospect in forensic application for diatom detection，and leads to easy popularization in drowning diagnosis.