Microbial succession after death: genomic and culture-based insights from external sampling sites in forensic science

Post-mortem microbial communities (microbiota and microbiome) have emerged as promising tools for forensic investigations, particularly in estimating the post-mortem interval (PMI). However, experimental variability in sampling protocols, analytical methods, and reporting standards has limited the comparability and reproducibility of findings across studies.

A systematic review was conducted in accordance with PRISMA guidelines to evaluate the current literature on human post-mortem microbiota and microbiome. Inclusion criteria focused on studies that examined microbial communities in human cadavers using culture-based techniques, next-generation sequencing (NGS), or both. Data were extracted regarding sample types, microbial targets, analytical methods, decomposition stages, insect activity, and study objectives.

A total of 24 studies were included, revealing substantial heterogeneity in methodological approaches. NGS techniques dominated recent literature, targeting bacterial 16S rRNA gene sequences to characterize microbial succession during decomposition. While some studies have shown promising correlations between microbial taxa and PMI, the inconsistent use of controls and variable decomposition conditions impeded cross-study comparisons. Culture-based approaches were generally limited to early investigations and provided narrower taxonomic resolution.

Despite encouraging results, the forensic application of post-mortem microbiome and microbiota remains hindered by methodological inconsistencies and a lack of standardization. Establishing unified protocols and adopting interdisciplinary approaches will be essential for validating microbial signatures as reliable forensic tools.