Dynamics of the oral microbiota as a tool to estimate time since death

Abstract

The 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 gastrointestinal tract. Upon death, the indigenous microorganisms lead to the decomposition of the carcass. Therefore, the oral cavity and gastrointestinal 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 individuals (one male and two female) donated to the University of Tennessee Forensic Anthropology Center for the W.M. Bass Donated Skeletal Collection were studied. Oral swab samples were taken daily 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 during the decomposition process. Firmicutes and Actinobacteria are the predominant phyla in the fresh stage. The presence of Tenericutes corresponds to bloat stage. Firmicutes is the predominant phylum in advanced decay, but the Firmicutes community is 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 postmortem interval, from an ecological rationale.

Temporal dynamics of microbiota before and after host death

“…Consistent with earlier studies [ 13 , 47 ], our analysis shows that the relative abundance of common members of the microbiota ranges widely, displaying various temporal dynamics that testify to the existence of different microbial lifestyles. Indeed, forensic science uses these diverse dynamics to estimate the time since host death [ 12 , 56 ], although this method is typically not applied to invertebrates.…”

“…2 ), a phylum commonly observed in living vertebrates and their decomposing carcasses [ 13 , 47 ]. Furthermore, Actinobacteria, also common in decomposing vertebrates [ 13 , 47 ] were found only in association with the medium used in our study (Fig. 2 ).…”

Cadaver Thanatomicrobiome Signatures: The Ubiquitous Nature of Clostridium Species in Human Decomposition

“…Thanatomicrobiome studies have determined that there is extremely rapid postmortem overgrowth of Clostridium spp. within decaying internal body sites (e.g., blood, bone marrow, liver, prostate) ( Clement et al, 2016 ; Javan et al, 2016a , b , Adserias-Garriga et al, 2017a , b ; Thomas et al, 2017 ; Zhao et al, 2017 ). Human decomposition is a multifactorial process mediated by microbes, which inhabit, proliferate, and die externally and internally throughout dead biomass ( Javan et al, 2016a , b ).…”

Relationship between acetaldehyde concentration in mouth air and characteristics of microbiota of tongue dorsum in Japanese healthy adults: a cross-sectional study

“…Each sample was collected from the median area of the tongue dorsum using a swab (men-tip ® ) that had been previously wetted by immersion in 5 mL of pure water and then rolled over the sampled surface using moderate pressure (21 g) and circular motion. 22 The 12 samples then were extracted (as described below) to permit investigation of the characteristics of the respective microbiomes.…”