Microbial succession patterns for postmortem interval estimation in decomposed mouse cadavers: A comparative study of mechanical asphyxia and hemorrhagic shock

Estimating the postmortem interval (PMI) is crucial in forensic science. Recent studies suggest microbial community succession patterns as a promising tool for PMI inference. This study examines how the cause of death, specifically mechanical asphyxia and hemorrhagic shock, influences microbial succession. By utilizing 16S amplicon sequencing, the study characterizes the succession patterns of microbial communities in different body parts (facial skin and cecal tissue) and applies random forest regression to develop PMI inference models. The results revealed significant differences in the decomposition processes between mechanical asphyxia and hemorrhagic shock. Determining the PMI based solely on postmortem phenomena proved challenging. Microbial communities in facial skin and cecal tissue-two distinct body parts from a decomposing corpse with the same cause of death-showed considerable variation, and the microbial composition in cecal tissue also differed between the two causes of death. The regression model, based on microbiota data at the family level, demonstrated the best performance. Specifically, eight bacterial families, including Enterobacteriaceae and Corynebacteriaceae, in facial skin were identified as predictors of PMI in corpses decomposed due to mechanical asphyxia, with an average absolute error of 2.15 ± 0.85 days. In contrast, 28 bacterial families, such as Lachnospiraceae and Clostridiales_NA, in cecal tissue were found to predict the PMI of corpses decomposed due to hemorrhagic shock, with an average absolute error of 2.52 ± 0.74 days. These findings provide a valuable microbial dataset for advancing forensic PMI studies.