Aims: This study assessed, for forensic purposes, the feasibility of genotypically matching oral streptococci recovered from recent human bite marks with those from the teeth of the biter.
Methods and results: Streptococci were isolated from the incisors of eight volunteers. Arbitrarily primed PCR (AP-PCR) distinguished 106 streptococcal genotypes among the participants, each harbouring at least eight distinct strains. In a crime simulation, a sample from an experimental bite mark was analysed by an experimenter unaware of its origin. The bacteria were unambiguously matched to the biter by comparing the amplicon profiles with those from the eight participants. In contrast, bacteria from an additional bite mark (not generated by one of the original participants) could not be matched to any of the eight participants. Between 20 and 78% of catalogued bacterial genotypes were recovered 12 months later from each participant. Throughout the study period, none of the bacterial genotypes were shared between participants.
Conclusions: Streptococci isolated from recent bite marks can be catalogued by AP-PCR and matched to the teeth responsible for the bite.
Significance and impact of the study: The study provides 'proof of concept' that genotypic analysis of streptococci from bite marks may provide valuable forensic evidence in situations where the perpetrator's DNA cannot be recovered.