Title Comparing "Streptococci" DNA on the Salivary Residue of a Bite Mark with That From a Suspect’s Teeth Could Possibly Be an Option to Identifying the Biter Within Reasonable Certainty
Clinical Question For a bite mark that included an associated salivary residue, would sequence comparison of streptococcal DNA from a salivary residue in the bite mark area and the suspect’s mouth be a viable pathway to possible identification of the biter with reasonable certainty when compared to traditional bite mark analysis?
Clinical Bottom Line 3 experimental studies, one of which was single-blind, demonstrated that comparison of various streptococcal DNA sequences from a bite mark and a group of individuals linked the corresponding biter and bite mark.
Best Evidence  
PubMed ID Author / Year Patient Group Study type
(level of evidence)
22638842Hsu/201224 healthy volunteers with self-inflicted bite wounds.Laboratory study
Key results24 teeth (incisor) samples, 19 bite marks, and 10 skin samples generated streptococcal amplicons. 14, 2, and 5 unique amplicons were found between the teeth, bite marks, and skin samples, respectively. The unique amplicons between the incisors and skin did not appear in any other incisor or skin sample. Unique amplicons from incisor samples often reappeared in their corresponding bite mark sample. The 2 unique amplicons from the bite mark samples did not appear in their corresponding incisor or skin sample.
23284761Kennedy/201216 unrelated adult volunteers with self-inflicted bite wounds on upper arms.Laboratory study
Key resultsStreptococcal genes for 16S ribosomal RNA (16S rRNA), 16S–23S intergenic spacer (ITS), and RNA polymerase beta subunit (rpoB) were compared between the subjects’ teeth and bite marks. The greatest amount of identical reads was between the teeth and their corresponding bite mark. For 16s rRNA, ITS, and rpoB, the average proportion of identical reads between bite marks and teeth samples were 0.31, 0.41, and 0.31, respectively. Average proportions of reads for non-corresponding samples were respectively 0.11, 0.20, and 0.016. The probabilities of correctly distinguishing corresponding and non-corresponding samples were 0.99, 0.92, and 1.0, respectively.
16238758Rahimi/20058 healthy volunteers; no antiseptic mouthwash or antibiotics for 3 months prior.Laboratory study
Key resultsArbitrarily primed PCR (AP-PCR) found 106 genetically distinguishable streptococcal strains among the volunteers. Between 8 and 23 genotypes were recovered from each participant, and the 2 most populous genotypes for each volunteer composed more than 35% of the sample. None of the genotypic profiles of a volunteer’s flora were identical to those of another volunteer. Comparison of the genotypes sampled from the bite mark only matched those of participant #4 (the biter). Furthermore, none of the 8 volunteers’ oral "Streptococci" could be linked to an additional bite mark committed by a 9th volunteer. 20-78% of cataloged bacterial genotypes were recovered one year later from each participant. The experimenter was unaware of the origin of the bite mark and the samples as this was a crime simulation.
Evidence Search "Bites, Human"[Mesh] AND "Streptococcus"[Mesh]
Comments on
The Evidence
None of the studies found actually compared the "Streptococci" DNA analysis with traditional bite mark analysis (the gold standard).
Applicability The evidence demonstrates that comparing "Streptococci" found on the salivary residue of a bite mark with that of a suspect’s teeth may possibly be a viable option to identifying the biter within some reasonable certainty. This approach to bite mark analysis could be applicable in the identification of an individual from a limited number of suspects. However, due to the small sample size of each study, the frequency at which specific oral streptococcal genotypes among either the general or a particular population is not yet known. This may be valuable supportive evidence against a suspected biter.
Specialty (Oral Medicine/Pathology/Radiology)
Keywords bite mark oral flora forensic odontology dna sequence analysis microbiology
ID# 2651
Date of submission 03/31/2014
E-mail gomezjr@livemail.uthscsa.edu
Author Jaime R. Gomez, II
Co-author(s) e-mail
Faculty mentor David R. Senn, DDS
Faculty mentor e-mail senn@uthscsa.edu
Basic Science Rationale
(Mechanisms that may account for and/or explain the clinical question, i.e. is the answer to the clinical question consistent with basic biological, physical and/or behavioral science principles, laws and research?)
None available
Comments and Evidence-Based Updates on the CAT
None available