Forensic insights from shotgun metagenomics: Tracing microbial exchange during sexual intercourse

The microbiome is becoming an emerging field of interest within forensic science with high potential for individualization; however, little is known about bacterial species specific to the genital area or their ability to transfer between individuals during sexual contact. In this proof-of-concept study, we investigated microbial transfer dynamics in seven monogamous, heterosexual couples by collecting pre- and post-sexual intercourse samples from their genital areas, including penile, vaginal, and labial locations. Utilizing Shotgun Metagenomic Sequencing, we sequenced the microbial profiles of these samples. Our findings reveal significant transfer from the vaginal microbiome onto the penile microbiome, predominantly originating from the labial genitalia. Moreover, strain analysis unveiled distinct differentiation between the same species of bacteria across individuals, underscoring the potential for microbial forensics to distinguish individuals. This study contributes to our understanding of microbial transfer during sexual contact and highlights the forensic implications of the genital microbiome.