Microbiology in Forensic Medicine

Microbial forensics is the study area that applies knowledge on microbiology to the challenges of forensic medicine, resulting promising but far from universal acceptance. Notwithstanding, this relatively novel sub-domain of medicinal forensics has laid grounds for an encouraging partnership that, due to its short existence, is in need of globalised methodological standardisation (1, 2). Once a consistent globally accepted set of guidelines emerge, its associated tools and paradigms will become as ubiquitous as microorganisms themselves. Microorganisms will then be providing reliable traceable evidence, crucial in the investigational process, be it in the course of a crime enquiry (3, 4), as an attempt to control the widespread of an epidemic (e.g., the recent tracking of coronavirus outbreak to patient zero and its point source), or even as pointers towards the most adequate treatment response when time is a constraint (5).

It is undeniable that microorganisms are becoming increasingly relevant in Forensic Medicine as professionals in the area build a more robust understanding of the intrinsic specificities of microbiomes, particularly due to the present capabilities of the biomolecular technologies at their disposal (6). Polymerase chain reaction (PCR), quantitative PCR (qPCR), fluorescent dyes and genetic probes, etc, individually or combined, empower the investigator, even when samples are minute or almost inexistent (7).

But what exactly makes the case for microbial forensics as a reputed science? The answer is simple and it is known by field experts as ‘predictable ecologies’ (8, 9). In simple terms this is defined by the application of undoubtful standardised methodologies that go from analysing a multicomplex ‘microbiome’ to ultimately relate it to an individualised ecology. Ergo, helping to accurately determine racial traits, geographical origin and other physiological singularities (6), link dynamic bodily fluids (e.g., vaginal, salivary, etc.) to specific individuals (10), generate exclusion hypothesis (11) supported by mathematical algorithms and predictive in silica models that greatly reduce apparent biological confounders (e.g., as with human twins), efficiently identify individual differences based on behavioural aspects and environmental exposure (12), analyse post-mortem, bodily decay and the agonal period (3), predict efficient medical approaches upstream to the infection cascade (13) and so forth.

[1] Aggarwal P, Chopra A, Gupte S, Sandhu S (2011). "Microbial forensics - An upcoming investigative discipline". Journal of Indian Academy of Forensic Medicine; 33.

[2] Fernandez-Rodriguez A, Cohen M, Lucena J, Van de Voorde W, Angelini A, Ziyade N, et al. (2015). "How to optimise the yield of forensic and clinical post-mortem microbiology with an adequate sampling: a proposal for standardisation". European Journal of Clinical Microbiology; 34.

[3] Metcalf J, Carter D, Knight R (2016). "Microbiology of death". Current biology : CB; 26:R561-R563.

[4] Metcalf JL (2019). "Estimating the postmortem interval using microbes: Knowledge gaps and a path to technology adoption". Forensic Science International: Genetics; 38:211-218.

[5] Engstrom-Melnyk J, Rodriguez PL, Peraud O, Hein RC. Chapter 5 - Clinical Applications of Quantitative Real-Time PCR in Virology. In: Sails A, Tang Y-W, editors. Methods in Microbiology. 42: Academic Press; 2015. p. 161-197.

[6] Hampton-Marcell J, Lopez J, Jack G (2017). "The human microbiome: an emerging tool in forensics". Microbial Biotechnology; 10:228-230.

[7] Kuiper I (2016). "Microbial forensics: next-generation sequencing as catalyst". EMBO reports; 17(8):1085-1087.

[8. Riedel S (2014). "The Value of Postmortem Microbiology Cultures". Journal of Clinical Microbiology; 52(4):1028.

9. Gunn A, Pitt S (2012). "Microbes as forensic indicators". Tropical biomedicine; 29:1-20.

10. Leake SL, Pagni M, Falquet L, Taroni F, Greub G (2016). "The salivary microbiome for differentiating individuals: proof of principle". Microbes and Infection; 18(6):399-405.

11. Costello EK, Lauber CL, Hamady M, Fierer N, Gordon JI, Knight R (2009). "Bacterial Community Variation in Human Body Habitats Across Space and Time". Science; 326(5960):1694.

12. Wu H, Zeng B, Li B, Ren B, Zhao J, Li M, et al. (2018). "Research on oral microbiota of monozygotic twins with discordant caries experience - in vitro and in vivo study". Scientific Reports; 8(1):7267.

13. Hemarajata P, Baghdadi JD, Hoffman R, Humphries RM (2016). "<span class="named-content genus-species" id="named-content-1">Burkholderia pseudomallei</span>: Challenges for the Clinical Microbiology Laboratory". Journal of Clinical Microbiology; 54(12):2866.

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