Dynamics of the Oral Microbiota as a Tool to Estimate Time Since Death

Abstract

Oral cavity harbors one of the most diverse microbiomes in the human body. It has been shown to be the second most complex in the body after the gastro- intestinal tract. Upon death, the indigenous microorganisms lead the decomposition of the carcass. Therefore, oral cavity and gastro-intestinal tract microbiomes, play a key role in human decomposition. The aim of the present study is to monitor the microbiome of decaying bodies on a daily basis and to identify signature bacterial taxa, that can improve postmortem interval estimation.

Three donated individuals (one male and two females) to the University of Tennessee Forensic Anthropology Center for the W. M. Bass Donated Skeletal Collection were studied. Oral swab samples were daily taken throughout the different stages of cadaveric putrefaction. DNA was extracted and analyzed by next generation sequencing techniques.

The three cadavers showed similar overall successional changes along decomposition process. Firmicutes and Actinobacteria are the predominant phyla in the fresh stage. Tenericutes presence corresponds to bloat stage. Firmicutes is the predominant phyla in advanced decay, being that Firmicutes community a different one from the predominant Firmicutes of the fresh stage.

This study depicts the thanatomicrobiome successional changes in the oral cavity, and highlights its potential use in forensic cases as a quantitative and objective approach to estimate PMI, from an ecological rationale.

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