It's been said that people can be judged by the company they keep. New research from Michigan State University shows that what's true for the living also is true for the dead.
The study, published in the current issue of Scientific Reports, shows that the postmortem microbiome – populations of micro-organisms that move in after death – can provide crucial insights into public health. What's telling is that regardless of many factors – sex, ethnicity or even type of death – the microbiome is consistent and distinct, depending on the number of days after death.
Based on the growing number of partnerships between MSU forensic entomologists and medical examiners, police and medical communities are beginning to see the value this research can provide. Case in point is the interdisciplinary research happening between MSU and the Wayne County Medical Examiner's Office.
"We're the only university routinely providing kits to collect microbial and bug samples from bodies as part of ongoing investigations," said Jennifer Pechal, MSU forensic entomologist and microbial ecologist and the study's lead author. "It's now standard protocol at the Wayne County Medical Examiner's Office, and data from more than 1,600 cases have been collected so far."
The partnership initially began to better understand the bugs and microbes present and what they can tell investigators about the recently deceased. Just as the TV show says, the first 48 hours of an investigation are critical. The organisms found on a body can help estimate the time of death.
"The microbial stopwatch, as it has been recently called, is a telling timepiece that can assist us in determining when someone died," said Eric Benbow, MSU forensic entomologist and microbial ecologist and study co-author. "It's comparable to a town with a changing population: a company starts up, and an entire new population moves in. In death, that microbial population is different after two days, and it completely turns over again a few days later."
MSU kits and the collection protocol are now regularly used in death investigations. One noteworthy case involves a mother who stored her two dead children in a freezer. The microbial data were the first used to understand how the postmortem microbiome changes in unusual circumstances of death and concealment, in this case when bodies were frozen.
The ever-growing dataset is painting a picture of the public health – of the living – including many populations that are underserved and understudied by the medical community. For the first time, MSU is demonstrating that sampling the postmortem microbiome may have public health surveillance importance like monitoring the diversity and frequency of antibiotic resistant genes from the general population.
Additionally, the victim may have died of a drug overdose, but the research also revealed that the microbes can show that the person suffered from a heart disease.
"During the first 48 hours, the samples we've gathered from a predominantly industrial-urban population confirmed that microbial biodiversity is a predictor of the host's health conditions, such as heart disease, when they were living," Pechal said. "We've demonstrated that this microbiome could be an effective tool for assessing the health of living populations."
MSU's reputation is growing in this realm, and other agencies around the world are noticing. Along with partnerships with Genesee County (Michigan) and other medical examiners across the Midwest, MSU has forged agreements in France, Italy and Austria.
In late April, Pechal and Benbow will participate in the European Association of Forensic Entomology in Munich. After the conference, they will meet with their partners in Salzburg, Austria, to fine tune their international postmortem protocols.
Explore further: Researchers estimate time since death using necrobiome
A large-scale survey of the postmortem human microbiome, and its potential to provide insight into the living health condition, Scientific Reports, volume 8, Article number: 5724 (2018) doi:10.1038/s41598-018-23989-w