Dr. Gulnaz Javan

The post-mortem interval, or time since death, is a crucial factor in homicide investigations. Scientists from all different fields of expertise have attempted to solve part of the forensic puzzle: bones experts look at tiny cracks in decomposed remains, entomologists look at the growth of insects, some chemists have gauged the changes in the makeup of blood and the odor of putrefying gases, and other biologists have looked at the microscopic life that grows in the guts and mouth of a corpse after life has ceased.

Now a team from Alabama State University has taken a new tack on tracking the changes that death wreaks on human remains by looking inside a new target: the liver and spleen bacteria, they report in the journal Frontiers in Microbiology.

Their theory: the internal organs may show a steady rate of change not affected by environmental or exposure factors – and could present a more predictable post-mortem interval.

“Thanatomicrobiome studies are different from postmortem oral microbiome and body farm studies because internal sites and blood are not subjected to exogenous environmental factors such as weather and scavenger activity like those associated with external body parts,” said Gulnaz Javan, an associate professor of forensic science, who runs the Thanatos Laboratory at Alabama State. “Additionally, the thanatomicrobiome is not immediately affected by gut-associated microorganisms that proliferate rapidly, depending on the cause of death.”

The team looked at the species of Clostridium bacteria (one species of which is the C. difficile bacteria known for causing illness) and found that the 16S rRNA gene in the bacteria could be an indicator of nothing less than the “Postmortem Clostridium Effect.”

From 45 cadavers, they sequenced the contents of the livers and spleens from the patients. The bodies were in the early processes of death, from the fresh to bloat stages. Each sample from the Alabama Department of Forensic Sciences and the Office of the District One Medical Examiner in Pensacola, Fla., yielded 10 mg of tissue, which was processed, quantified by the ThermoFisher Scientific NanoDrop2000, and then amplified for sequencing at RTL Henomcs in Lubbock, Tex., and then sequenced by the Illumina MiSeq.

The liver was chosen because of its microbial diversity-- it's the largest solid organ, and receives blood from two sources, said Javan, in an email interview with Forensic Magazine. The spleen was selected because it is the largest ductless gland and the bulkiest single lymph organ in the body, she added.

The authors concluded that Clostridium grows fast, and grows without oxygenated blood – and is therefore a rich and untapped source of death microbiome data, they conclude.

“Conceivably, thanatomicrobiome analysis will be used to build predictive Thanatos models employed the PCE that can further designate the recovery of distinct community types associated with postmortem microbial communities,” they write.

Javan said that it’s too early to tell if it’s a better death clock. But it could be, she added. The continuing work she and her Thanatos Laboratory are calling the Human Postmortem Microbiome Project is expanding beyond Alabama and Florida to include death data from Finland and Italy, among other places.

“The project is ongoing and currently we cannot say that Clostridium is a better gauge than some other flora in the corpse yet,” she stated.