“Touch microbiome” as a potential tool for forensic investigation: A pilot study

Noemi Procopio,Flavia Lovisolo,Giulia Sguazzi,Stefano Ghignone,Samuele Voyron,Mario Migliario,Filippo Renò,Federica Sellitto,Gabriella D'Angiolella,Pamela Tozzo,Luciana Caenazzo,Sarah Gino

doi:10.1016/j.jflm.2021.102223

Abstract

Human skin hosts a variety of microbes that can be transferred to surfaces (“touch microbiome”). These microorganisms can be considered as forensic markers similarly to “touch DNA”. With this pilot study, we wanted to evaluate the transferability and persistence of the “touch microbiome” on a surface after the deposition of a fingerprint and its exposure for 30 days at room temperature. Eleven volunteers were enrolled in the study. Skin microbiome samples were collected by swabbing the palm of their hands; additionally, donors were asked to touch a glass microscope slide to deposit their fingerprints, that were then swabbed. Both human and microbial DNA was isolated and quantified. Amelogenin locus and 16 human STRs were amplified, whereas the V4 region of 16 S rRNA gene was sequenced using Illumina MiSeq platform. STR profiles were successfully typed for 5 out of 22 “touch DNA” samples, while a microbiome profile was obtained for 20 out of 22 “touch microbiome” samples. Six skin core microbiome taxa were identified, as well as unique donor characterizing taxa. These unique taxa may have relevance for personal identification studies and may be useful to provide forensic intelligence information also when “touch DNA” fails. Additional future studies including greater datasets, additional time points and a greater number of surfaces may clarify the applicability of “touch microbiome” studies to real forensic contexts.

Highlights

Materials and MethodsConditions and not having taken antibiotics and/or antifungals in the 15 days prior to the sampling
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Since the focus of the paper is to evaluate the possibility of using microbiome analysis as a potential tool to achieve personal identification, in cases where “touch DNA” analysis fails, we fully reported below only the steps required for the analysis of the touch microbiome and its associated results, whereas the analyses carried out for the “touch DNA” and consequent results are summarized in the Supplementary Material

Summary

Materials and Methods

Conditions and not having taken antibiotics and/or antifungals in the 15 days prior to the sampling. “Skin samples” were collected by sliding two sterile swabs moistened with physiological water over the entire palm surface, including fingers, of the dominant hand for 15 seconds. Swabs were stored at -20 °C for 30 days, after which DNA (both bacterial and human) was extracted. The same donors were asked to touch two glass microscope slides with all five fingers for about ten seconds in order to deposit their fingerprints all around the surface of the slide, and after 30 days at room temperature the deposited fingerprints were swabbed in order to obtain a “glass fingerprint sample”. The idea was to simulate the random release of genetic material (both bacterial and human) on surfaces touched by the subject (called respectively “touch microbiome” and “touch DNA”). Since the focus of the paper is to evaluate the possibility of using microbiome analysis as a potential tool to achieve personal identification, in cases where “touch DNA” analysis fails, we fully reported below only the steps required for the analysis of the touch microbiome and its associated results, whereas the analyses carried out for the “touch DNA” and consequent results are summarized in the Supplementary Material

Microbiome Extraction and Analysis

Statistical Analysis

Microbiome Analysis

Discussion

Conclusions