Microbiome in Death and Beyond: Current Vistas and Future Trends

Abstract

Forensic medicine has, for a long time, been relying on biochemical, anthropologic, and histopathologic evidences in solving various investigations. However, depending on the method used, lengthy sample processing time, scanty sample, and less sensitivity and accuracy pervade these procedures. Accordingly, newer arenas such as the thanatomicrobiome have come forward to aid in its quandaries; furthermore, the parallel advances in genomic and proteomic techniques have complemented and are still emerging to be used in forensic experiments and investigations. Postmortem interval (PMI) is one of the most important aspects of medico-legal investigations. The current trend in PMI estimation is toward genomic analyses of autopsy samples. Similarly, determination of cause of death, although a domain of medical sciences, is being targeted as the next level of forensic casework. With the current trend in laboratory sciences moving to the discovery of newer disease-specific markers for diagnostic and prognostic purposes, the same is being explored for the determination of the cause of death by using techniques such as Real-Time PCR, DNA micro-array, to Next-Gen Sequencing. Establishing an individual’s biological profile has been done using medicolegal methods and anthropology as well as bar-bodies/Davidson bodies (gender determination); and in cases where the determination of age/gender is a challenge using morphological characteristics; the recent advances in the field of genomics and proteomics have played a significant role, e.g., use of mitochondrial DNA in age estimation and in maternity disputes. The major hurdle forensic medical research faces is the fact that most of the studies are conducted in animal models, which are often difficult to mimic in human and real-time scenarios. Additionally, the high accuracy required in criminal investigations to be used in a court of law as evidence has prevented these results to come out of the labs and be used to the optimum. The current review aims at giving a comprehensive and critical account of the various molecular biology techniques including “thanatogenomics,” currently being utilized in the veritable fields of forensic medicine.

MALDI-TOF Mass Spectrometry Analysis and Human Post-Mortem Microbial Community: A Pilot Study

“…The HPM became increasingly different from starting communities over time in the internal organs as well as at skin sites, as observed in other reports [ 9 , 10 ]. In previous studies Proteobacteria abundance has been found to increase overall throughout decomposition in animal and human models while Firmicutes and Bacteroidetes decrease [ 42 , 43 ]. Such expected shifts in the structure of the culturable bacterial community over decomposition is also detectable by MALDI-TOF but depends on the anatomical site and insect colonization [ 19 ].…”

Microbial DNA in human nucleic acid extracts: Recoverability of the microbiome in DNA extracts stored frozen long-term and its potential and ethical implications for forensic investigation

“…The natural fluctuations in the number and types of microorganisms associated with a cadaver have great potential to be harnessed for the development of precise and accurate methods for estimation of the PMI [33][34][35][36]. Currently, PMI is generally estimated based on changes to the body, including cooling, lividity, and rigor mortis, followed by gross morphological changes.…”

“…Organ thanatomicrobiome analyses suggest that facultative anaerobes, such as Lactobacillus, predominate in the "short PMI" timeframe, while in a "long PMI" timeframe a predominance of obligate anaerobes like Clostridium is observed [53]. Notably, Firmicutes (e.g., Clostridium, Peptoniphilus, and Bacillus) represent a stable and constant biomarker in microbial communities derived from different body locations [33]. Even the manner of death (natural, accidental, suicide, homicide, undetermined) has been shown to influence the thanatomicrobiome in various organs [33,39,52].…”

Microbial Clock: A review on forensic microbiology for crime scene investigations

“…The onset of fluid-filled blisters on the skin and skin slippage, in which huge sheets of skin slough off the body, are the initial signs. (Roy et al, 2021) However, the body has adjusted to its surroundings (algor mortis), blood has accumulated in the body, generating skin darkening (livor mortis), and Because of the increasing alkalinity, the cytoplasm of cells has dissolved (rigor mortis). When a large enough number of cells burst, nutrition fluids emerge available, and the putrefaction might occur (Vass, 2001).…”