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P154 – The Heart-Liver Microbiome Combination Enhances Early PMI Estimation in High-Temperature Environments
Objectives
Accurate estimation of the postmortem interval (PMI) under high-temperature conditions remains a challenge in forensic investigations. Despite the proven temporal value of microbial clocks, prevailing forensic models rely heavily on external or single-tissue niches, leaving the complex spatiotemporal dynamics of internal organ microbiomes largely unexplored. This study aims to decode the species-level microbial successional patterns across multiple internal organs during early decomposition. By doing so, we seek to establish a biologically interpretable, optimal multi-tissue sampling protocol that enhances PMI estimation accuracy while minimizing forensic sampling redundancy.
Material and methods
A mammalian decomposition model utilizing 36 Sprague-Dawley rats was established under simulated high-temperature conditions (mean ambient temperature: 35℃). Microbiota from five distinct internal organs-heart, liver, spleen, lung, and skeletal muscle-were systematically sampled at PMIs of 0, 1, 2, 3, 5, and 7 days. Full-length 16S rRNA sequencing was employed to achieve species-level taxonomic resolution. To evaluate predictive performance, single-tissue and multi-tissue integration models were constructed using Elastic Net algorithms and validated using rigorous cross-validation.
Results and conclusions
Full-length 16S sequencing revealed a distinct species-level shift in community composition emerging around postmortem day 3, indicating a critical ecological transition point during early decomposition. Crucially, microbial succession exhibited strong organ-specific patterns. Among single-tissue models, the heart consistently demonstrated superior predictive accuracy, likely driven by its distinct postmortem ischemic microenvironment and structural density, which selectively filter microbial colonization. Building upon this, multi-tissue integration models revealed that the heart-liver combination provided the optimal predictive performance, achieving an RMSE of 0.81 ± 0.23 days within the 7-day PMI window. Notably, incorporating additional organs (up to all five) yielded no further improvement. These findings demonstrate that strategic tissue selection—rather than indiscriminate multiplexing—is the primary determinant of model efficacy. This study not only highlights the heart-liver axis as a robust forensic biomarker reservoir but also provides a cost-effective, targeted sampling framework for highly accurate PMI estimation in challenging environments.
Authors
- Xin Huang (Fudan University, China)
- Chengtao Li (Fudan University, China)
- Suhua Zhang (Fudan University, China)
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