Temporal dynamics changes in the vaginal fluid microbiome: Implications for body fluid identification and estimating time since deposition (TsD) for forensics

• Published in: Forensic science international Vol. 364; p. 112219
• Main Authors: Ye, Linying, Liao, Lili, Lan, Jiangwei, Huang, Litao, Du, Jieyu, Zhang, Xiaofeng, Lun, Miaoqiang, Zhu, Bofeng, Liu, Chao, Chen, Ling
• Format: Journal Article
• Language: English
• Published: Ireland Elsevier B.V 01.11.2024; Elsevier Limited
• Subjects: Adult; Bacteria; Bacteria - classification; Bacteria - genetics; Bacteria - isolation & purification; Body fluid identification; Body fluids; Body Fluids - microbiology; chronic exposure; crime; Deposition; DNA, Bacterial; Error analysis; Exposure; feces; Feces - chemistry; Feces - microbiology; Female; Forensic medicine; Forensic science; Forensic Sciences; High-Throughput Nucleotide Sequencing; Humans; Indoor environments; Lactobacillus; Lactobacillus - isolation & purification; Male; Medical research; Microbial activity; Microbial changes; microbiome; Microbiomes; Microbiota; Microorganisms; Next-generation sequencing; Prediction models; RNA, Ribosomal, 16S; rRNA 16S; Saliva; Saliva - chemistry; Saliva - microbiology; Semen; Semen - microbiology; Sequence Analysis, DNA; Sex crimes; Sexual assault; Skin - microbiology; Taxonomy; temporal variation; Time dependence; Time Factors; Time series; Time since deposition (TsD); Vagina; Vagina - microbiology; Vaginal fluids; United States > US; China; Microbial changes; Exposure; Body fluid identification; Vaginal fluids; Time since deposition (TsD)
• ISSN: 0379-0738; 1872-6283; 1872-6283
• DOI: 10.1016/j.forsciint.2024.112219

Vaginal fluid analysis plays a crucial role in sexual assault investigations. However, vaginal fluid found at crime scenes is usually subject to a certain duration of exposure. This study thus aimed to assess the influence of different durations of exposure to indoor environment on the vaginal microbiota. The 16S rDNA high-throughput sequencing was used on vaginal fluid samples exposed for short-term (30 days) and long-term (240 days), respectively. Despite potential contamination from environmental microorganisms, particularly following long-term exposure, the results indicated that the vaginal microbiota after exposure was still dominated by Lactobacillus. Both in short-term and long-term exposure involving vaginal fluid, there were clusters with time-dependent characteristics, wherein the relative abundances of associated microbial genera showed a trend of increasing or decreasing over time. In addition, each bodily fluid presented with a unique array of dominant bacterial genera, enabling the differentiation of exposed vaginal fluid samples from other bodily fluids (semen, skin, saliva, feces) with a remarkable 98.75 % accuracy rate. Furthermore, the mean absolute error achieved by the long-term deposition time prediction model was 13.54 days. The mean absolute error for the short-term deposition time prediction model was notably lower, reaching just 2.05 days. In summary, this study investigates the variations in microbial communities within vaginal fluid subjected to different indoor exposure durations and explores their potential in body fluid identification and estimating the time since deposition, thereby contributing valuable supporting evidence in forensic investigations. •This study showed temporal changes in vaginal microbiome after exposure in an indoor environment for up to 240 days.•The exposed vaginal microbiome is still dominated by Lactobacillus, despite possible contamination by environmental microbes.•The random forest model distinguished the exposed vaginal fluid samples from other body fluids with high accuracy.•Changes in vaginal microbiota over time might have potential to estimate the time since deposition.