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Human DNA typing of maggot gut contents

Magni, P.A., Di Luise, E., Staiti, N., Spitaleri, S. and Romano, C. (2008) Human DNA typing of maggot gut contents. In: 6th Meeting European Association for Forensic Entomology (EAFE), 20 - 24 May 2008, Kolymbari, Crete.


During medical legal investigations larvae of Diptera are often collected from cadavers for Post Mortem Interval (P.M.I.) estimation purposes. Some publications suggested that the contents of the alimentary canal of such insects are suitable for human mithocondrial and nuclear DNA typing analyses. We aimed to collect human DNA from the crop of third instar maggots of Calliphora vicina (Robineau-Desvoidy, 1830), recovered from a dead body in the first stage of decomposition, partially mummified. Eight crops were included in each sample batch. All the sample batches were then conserved using different preservative method including waterless conditions (absence of any preservative), conservative liquids (ethanol 70%) and physical inactivation processes (boiling for 5 second before immersion or refrigeration at –20°C). In order to obtain the best yield DNA we performed several extraction methods: a) ChelexTM - (Biorad); b) DNA IQTM system extraction kit (Promega) and c) Qiagen™ DNA MicroKit. DNA yield and quality were compared with respect to different collections, storage and extraction methodologies; for this purpose the extracted samples were quantified via Real Time PCR. Our preliminary results indicated that ethanol based preservation dramatically decreased the quantity of typeable human DNA whereas preservation by simple refrigeration produced the best results. Moreover, while previous works indicated a storing temperature of -70°C, we obtained full 15 autosomal and 16 Y-chromosome loci profiles from specimen preserved at –20°C without any preservative liquid (waterless condition) which should be considered a major advantage for crime labs. Extraction methods based on the use of silica columns (Qiagen™ DNA MicroKit) showed the higher DNA yield and purity due to the purification steps included into the protocol. The autosomal and Y-STR complete profiles matched positively with a reference sample of the cadaver. The DNA concentration ranged between 0 and 270 pg/µl. Our data showed the suitability of DNA gut contents of fly larvae - recovered in real casework - for human STR-based identification. Moreover our results indicate that successful downstream analyses can be obtained by coupling simple refrigeration with silica column DNA extraction.

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