School of Forensic Medicine, Shanxi Medical University, Jinzhong, Shanxi, China.
Shanxi Key Laboratory of Forensic Medicine, Jinzhong, Shanxi, China.
Microbiol Spectr. 2024 Apr 2;12(4):e0248023. doi: 10.1128/spectrum.02480-23. Epub 2024 Mar 12.
Identification and the time since deposition (TsD) estimation of body fluid stains from a crime scene could provide valuable information for solving the cases and are always difficult for forensics. Microbial characteristics were considered as a promising biomarker to address the issues. However, changes in the microbiota may damage the specific characteristics of body fluids. Correspondingly, incorrect body fluid identification may result in inaccurate TsD estimation. The mutual influence is not well understood and limited the codetection. In the current study, saliva, semen, vaginal secretion, and menstrual blood samples were exposed to indoor conditions and collected at eight time points (from fresh to 30 days). High-throughput sequencing based on the 16S rRNA gene was performed to characterize the microbial communities. The results showed that a longer TsD could decrease the discrimination of different body fluid stains. However, the accuracies of identification still reached a quite high value even without knowing the TsD. Correspondingly, the mean absolute error (MAE) of TsD estimation significantly increased without distinguishing the types of body fluids. The predictive TsD of menstrual blood reached a quite low MAE (1.54 ± 0.39 d). In comparison, those of saliva (6.57 ± 1.17 d), semen (6.48 ± 1.33 d), and vaginal secretion (5.35 ± 1.11 d) needed to be further improved. The great effect of individual differences on these stains limited the TsD estimation accuracy. Overall, microbial characteristics allow for codetection of body fluid identification and TsD estimation, and body fluids should be identified before estimating TsD in microbiome-based stain analyses.IMPORTANCEEmerged evidences suggest microbial characteristics could be considered a promising tool for identification and time since deposition (TsD) estimation of body fluid stains. However, the two issues should be studied together due to a potential mutual influence. The current study provides the first evidence to understand the mutual influence and determines an optimal process for codetection of identification and TsD estimation for unknown stains for forensics. In addition, we involved aged stains into our study for identification of body fluid stains, rather than only using fresh stains like previous studies. This increased the predictive accuracy. We have preliminary verified that individual differences in microbiotas limited the predictive accuracy of TsD estimation for saliva, semen, and vaginal secretion. Microbial characteristics could provide an accurate TsD estimation for menstrual blood. Our study benefits the comprehensive understanding of microbiome-based stain analyses as an essential addition to previous studies.
从犯罪现场鉴定和推断体液痕迹的时间（TsD）可以为解决案件提供有价值的信息，但这对法医学来说一直是一个难题。微生物特征被认为是解决这一问题的有前途的生物标志物。然而，微生物群的变化可能会破坏体液的特定特征。相应地，不正确的体液鉴定可能导致不准确的 TsD 估计。两者之间的相互影响还不太清楚，限制了共同检测。在本研究中，唾液、精液、阴道分泌物和月经血样本在室内条件下暴露，并在八个时间点（从新鲜到 30 天）采集。基于 16S rRNA 基因的高通量测序用于描述微生物群落。结果表明，TsD 较长会降低不同体液痕迹的区分度。然而，即使不知道 TsD，鉴定的准确率仍然达到了相当高的水平。相应地，TsD 估计的平均绝对误差（MAE）显著增加，而不分体液体类型。月经血的预测 TsD 达到相当低的 MAE（1.54±0.39d）。相比之下，唾液（6.57±1.17d）、精液（6.48±1.33d）和阴道分泌物（5.35±1.11d）的需要进一步提高。个体差异对这些痕迹的巨大影响限制了 TsD 估计的准确性。总的来说，微生物特征允许共同检测体液鉴定和 TsD 估计，并且在基于微生物组的痕迹分析中，应该在估计 TsD 之前鉴定体液。
越来越多的证据表明，微生物特征可以被认为是鉴定和推断体液痕迹时间（TsD）的有前途的工具。然而，由于潜在的相互影响，这两个问题应该一起研究。本研究首次提供了理解相互影响的证据，并确定了用于法医未知痕迹共同检测鉴定和 TsD 估计的最佳过程。此外，我们将陈旧的痕迹纳入研究，用于鉴定体液痕迹，而不仅仅是像以前的研究那样只使用新鲜的痕迹。这提高了预测的准确性。我们已经初步验证了微生物群的个体差异限制了唾液、精液和阴道分泌物 TsD 估计的预测准确性。微生物特征可以为月经血提供准确的 TsD 估计。我们的研究有助于全面理解基于微生物组的痕迹分析，这是对以前研究的重要补充。
