An Investigation into the Effects of Freezing on the Microbiome of Human Cadavers

Background and Aims: The potential forensic applications of human microbiome studies have grown exponentially, particularly with regards to estimating postmortem interval based on microbial shifts during decomposition. These studies at human taphonomy facilities often use previously frozen cadavers, which are thawed before the start of any experiment. However, the effects of freezing and thawing on the process of decomposition and long-term development of the (thanato)microbiome remain largely unexplored. Two studies involving animal and human cadavers have shown temperature related changes to the microbiome. Hence, understanding how freezing human cadavers may affect the microbiome is crucial, as these studies suggest that it could potentially skew experimental results and interpretation. Methods: For this project, we collected swab samples from five anatomical locations of nine cadavers (oral, rectum, hand, foot, and neck). Swabs were collected from the cadavers prior to freezing at –20 °C, and after freezing and thawing. Analysis of the samples involves DNA extraction using Qiagen’s PowerSoil Pro kit. Microbial species identification will be carried out using DNA metabarcoding, targeting the 16S rRNA gene. Results: Processing of these samples is currently ongoing; however, results will be ready to be presented to the audience before the conference. Conclusions: The results from this study will be important in relation to standard operating protocols and sampling procedures at human taphonomy facilities worldwide and will provide insight into the validity of using previously frozen cadavers in microbiome studies. Finally, the results may provide useful information on the abundance and composition of microbiota for forensic case investigations involving frozen bodies.