Di Gloria Leandro, Baldi Simone, Curini Lavinia, Bertorello Sara, Nannini Giulia, Cei Francesco, Niccolai Elena, Ramazzotti Matteo, Amedei Amedeo
Department of Experimental and Clinical Biomedical Sciences, University of Florence, Italy.
Department of Experimental and Clinical Medicine, University of Florence, Italy.
FEBS J. 2025 Feb;292(4):796-808. doi: 10.1111/febs.17362. Epub 2024 Dec 17.
The advent of next-generation sequencing (NGS) technologies has made it possible to investigate microbial communities in various environments, including different sites within the human body. Therefore, the previously established belief of the sterile nature of several body sites, including human blood, has now been challenged. However, metagenomics investigation of areas with an anticipated low microbial biomass may be susceptible to misinterpretation. Here, we critically evaluate the results of 16S targeted amplicon sequencing performed on total DNA collected from healthy donors' blood samples while incorporating specific negative controls aimed at addressing potential bias to supplement and strengthen the research in this area. We prepared negative controls by increasing the initial DNA quantity through sequences that can be recognized and subsequently discarded. We found that only three organisms were sporadically present among the samples, and this was mostly attributable to bacteria ubiquitously present in laboratory reagents. Despite not fully confirming or denying the existence of healthy blood microbiota, our results suggest that living bacteria, or at least their residual DNA sequences, are not a common feature of human blood in healthy people. Finally, our study poses relevant questions on the design of controls in this research area that must be considered in order to avoid misinterpreted results that appear to contaminate current high-throughput research.
新一代测序(NGS)技术的出现使得研究包括人体不同部位在内的各种环境中的微生物群落成为可能。因此,包括人体血液在内的几个身体部位无菌的先前既定观念现在受到了挑战。然而,对预期微生物生物量较低的区域进行宏基因组学研究可能容易产生误解。在此,我们严格评估了对从健康供体血液样本中收集的总DNA进行的16S靶向扩增子测序结果,同时纳入了旨在解决潜在偏差的特定阴性对照,以补充和加强该领域的研究。我们通过可识别并随后丢弃的序列增加初始DNA量来制备阴性对照。我们发现样本中仅偶尔存在三种生物体,这主要归因于实验室试剂中普遍存在的细菌。尽管没有完全证实或否定健康血液微生物群的存在,但我们的结果表明,活细菌,或至少它们的残留DNA序列,并非健康人血液的常见特征。最后,我们的研究对该研究领域的对照设计提出了相关问题,为避免出现似乎污染当前高通量研究的误解结果,必须考虑这些问题。
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