Reacción a "Genital microbiome could help identify sexual offenders"

This study strengthens the idea that bacterial communities in the male and female genital tract can be exchanged during intercourse. By sequencing the 16S rRNA gene in vaginal and penile samples taken before and after sexual intercourse, the authors identified the transfer of specific bacterial signatures between partners. These findings are in line with previous studies that already suggested this microbial exchange in couples.

In addition, the researchers suggest that this type of analysis could be useful in the forensic field, especially in cases where human DNA cannot be detected. They also highlight that the bacterial fingerprint could extend the time window to identify sexual contact, exceeding the 48 hours after which the detection of sperm in vaginal samples is drastically reduced. However, the individual variability of the microbiome, together with the multiple factors that can influence the stability of these microbial signatures, such as personal hygiene, the use of barrier contraceptives and the natural dynamics of the microbiome, make further research necessary before considering a reliable practical application.

The concept of the ‘sexome’ as a forensic tool is fascinating, but there is still a long way to go before it can be used in courtroom practice. Accurate identification of microorganisms at the strain level and their stability over time are key challenges. In addition, the microbiome is not static: factors such as the time elapsed since contact or the presence of other biological fluids can influence the results. This study represents an interesting advance in the understanding of bacterial transfer between couples, but its viability in forensic investigations still requires validation in larger studies and in real-world settings.

Also, after reading the press release, I would like to make a technical clarification: the study sequences DNA, not RNA. Specifically, the gene (DNA) that encodes the 16S rRNA subunit is sequenced. I would also recommend removing the claim that the results are “down to the sub-species level,” as the data in the study do not reach that resolution.