Microbial Analysis of Bite Marks by Sequence Comparison of Streptococcal DNA

Abstract

Bite mark injuries often feature in violent crimes. Conventional morphometric methods for the forensic analysis of bite marks involve elements of subjective interpretation that threaten the credibility of this field. Human DNA recovered from bite marks has the highest evidentiary value, however recovery can be compromised by salivary components. This study assessed the feasibility of matching bacterial DNA sequences amplified from experimental bite marks to those obtained from the teeth responsible, with the aim of evaluating the capability of three genomic regions of streptococcal DNA to discriminate between participant samples. Bite mark and teeth swabs were collected from 16 participants. Bacterial DNA was extracted to provide the template for PCR primers specific for streptococcal 16S ribosomal RNA (16S rRNA) gene, 16S–23S intergenic spacer (ITS) and RNA polymerase beta subunit (rpoB). High throughput sequencing (GS FLX 454), followed by stringent quality filtering, generated reads from bite marks for comparison to those generated from teeth samples. For all three regions, the greatest overlaps of identical reads were between bite mark samples and the corresponding teeth samples. The average proportions of reads identical between bite mark and corresponding teeth samples were 0.31, 0.41 and 0.31, and for non-corresponding samples were 0.11, 0.20 and 0.016, for 16S rRNA, ITS and rpoB, respectively. The probabilities of correctly distinguishing matching and non-matching teeth samples were 0.92 for ITS, 0.99 for 16S rRNA and 1.0 for rpoB. These findings strongly support the tenet that bacterial DNA amplified from bite marks and teeth can provide corroborating information in the identification of assailants.

Comparative Evaluation of the Salivary and Buccal Mucosal Microbiota by 16S rRNA Sequencing for Forensic Investigations

“…Human microorganisms with their nucleic acids are regularly deposited and transferred in a manner similar to human DNA and can be used to identify criminal suspects (Schmedes et al, 2016). Moreover, bacterial DNA is circular and well protected by peptidoglycan, making bacterial DNA more resistant to degradation than human DNA (Kennedy et al, 2012;Leake et al, 2016). On the one hand, the human microbiome is highly individualized (Human Microbiome and Project Consortium, 2012), which makes it possible to apply the human microbiome for forensic personal identification, especially in the case of degraded DNA and low quantities of human DNA.…”

“…To date, highthroughput sequencing of 16S rRNA genes has been frequently used in forensic phylogenetic analyses of microbiomes, including the skin microbiome (Fierer et al, 2010;Wilkins et al, 2017), soil microbiome (Habtom et al, 2019), vaginal microbiome (Zou et al, 2016;Yao et al, 2021), and salivary microbiome (Stahringer et al, 2012;Leake et al, 2016). Moreover, previous studies have used high-throughput sequencing to analyze the salivary microbiome and bacterial DNA amplified from bite marks and teeth (Kennedy et al, 2012;Leake et al, 2016). The method of amplicon sequencing of 16S rRNA genes can be applied to analyze oral microbiome diversity for forensic investigations.…”

Assess The Diversity of Gut Microbiota Among Healthy Adults For Forensic Application

“…The feces sample contains host-microbial pro les that could provide insight into valuable individual information on digestion or diet habits as investigative clues and trial basis. In recent years, with the development of next-generation DNA sequencing technology and bioinformatic methods, the application of human microbiota to forensic personal identi cation has been studied in the saliva microbiome [2,3], skin microbiome [4][5][6][7], hair microbiome [8], etc.. However, the studies about fecal material have focused on cell type identi cation to determine the cellular origin of samples/DNA pro les for forensic practice [9,10], and there is little attention on gut microbiota for forensic personal identi cation.…”

Salivary signature in forensic profiling: A scoping review

“…[4] Literature also supports microbial analysis of bite marks to correlate specifically streptococcal DNA in saliva to that of suspect where human DNA availability is questionable. [1112] Hence, proper collection and analysis of salivary sample for oral microbiome signatures are performed in the following steps:…”