[Microbiomics‑Based Prediction of Postmortem Interval in Rats with Ethanol Exposure Combined with CO Poisoning]

To investigate the temporal changes of intestinal bacterial communities in rats that died from combined ethanol and carbon monoxide (CO) poisoning using microbiome analysis techniques, and to explore potential correlations between these changes and the postmortem interval (PMI).

Four experimental groups were established：fatal CO poisoning, fatal CO poisoning following ethanol exposure, ethanol exposure, and blank controls. Rectal specimens were collected at 0, 1, 3, 7, and 14 days postmortem. High-throughput sequencing of the 16S rRNA gene was employed to analyze bacterial communities. Bacterial diversity, relative abundance, and community differences were analyzed. A predictive model for PMI estimation using bacterial community succession patterns was constructed using a random forest algorithm.

The intestinal bacterial community structure of rats changed at both the phylum and genus levels within 14 days postmortem in the experimental groups. The PMI estimation model based on bacterial characteristics demonstrated good predictive performance across different experimental groups, with model fitting accuracies of 0.60, 0.59, 0.61 and 0.60 for each of the four groups. The average prediction error across all groups was approximately 1 day.

Ethanol exposure, CO poisoning, and the combined effects of ethanol exposure and CO poisoning all affect postmortem bacterial succession in rat cadavers. In forensic practice, it is recommended to adopt a predictive model specifically developed for the corresponding poisoning condition to improve the accuracy of PMI estimation.