Analysis of Post-Mortem Variations in the Microbiome of the Oral Cavity, Cornea, and Rectum: A Systematic Review of the Literature

The study of the human microbiome has recently emerged as a promising tool in forensic science, particularly in estimating the post-mortem interval (PMI) through the analysis of microbial succession. In this context, it is important to distinguish between microbiota—the community of microorganisms (bacteria, fungi, archaea) residing in a specific anatomical site—and the microbiome, which refers to the total genetic material of these microbial populations. Following death, these communities undergo predictable ecological transformations influenced by time, environmental conditions, and the intrinsic characteristics of the deceased. The term thanatomicrobiome describes microbial dynamics within internal tissues, while epinecrotic communities refer to microorganisms colonizing external body surfaces (Dash et al 2020). Most existing studies have concentrated on internal organs or soil associated with decomposition (Ahannach et al 2021), (Metcalf et al 2019). However, this review focuses on three anatomical regions—the oral cavity, cornea, and rectum—which are accessible for microbiological sampling without invasive procedures and thus comply with mortuary and legal constraints. Recent works using next-generation sequencing (e.g., 16S rRNA, metagenomics) have demonstrated that these body sites exhibit distinct and temporally structured microbial successions after death (Sguazzi et al 2022). This study aims to explore whether the current scientific literature supports the existence of consistent and site-specific patterns of microbial succession in the oral cavity, cornea, and rectum during the post-mortem interval. It further seeks to determine whether these microbial changes can be reliably correlated with factors such as the elapsed time since death (PMI), environmental conditions, and specific characteristics of the cadaver. Ultimately, the goal is to evaluate the potential of postmortem microbial succession as a forensic tool for estimating the PMI and enhancing our understanding of decomposition processes in forensic investigations.