Sandwich sample wrapped in a napkin was sent to the lab for DNA analysis for maggot or insect materials contamination. The DNA analysis samples were taken from the cheese, egg, meat and bread around the bite mark. There were "white granules" spread in the burger that were included in DNA analysis. DNA was extracted using Tissue Extraction kit on an automatic DNA extraction instrument. DNA was analyzed for standard DNA barcode for mitochondrial COI (cytochrome c oxidase I) gene as well as universal DNA mini-barcode for COI.
The results showed that the cheese was from cow, the meat was from pork. The egg did not produce any amplifiable DNA and no DNA sequence available. The bread had three types of DNA materials including wheat (Triticum aestivum), cow (Bos taurus) and beetle DNA (Ochthebius minimus, Dendroacalles anagaensis or Prosimulium arvum). Although universal DNA mini-barcode could not reproduce beetle DNA sequences due to quantity of the trace amount of beetle DNA, it is still possible that the sandwich was contaminated with beetle larva (such as mealworm), instead of "maggot (fly larvae)". In addition, the sandwich bread and meat was dissected under microscope and no "maggot" like larvae or worms were observed, suggesting the beetle larva perhaps only presented on the surface.