Perinatology Research Branch, Division of Obstetrics and Maternal-Fetal Medicine, Division of Intramural Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, U.S. Department of Health and Human Services, Detroit, MI, United States.
Perinatal Research Initiative in Maternal, Perinatal and Child Health, Wayne State University School of Medicine, Detroit, MI, United States.
Front Immunol. 2022 Feb 28;13:820366. doi: 10.3389/fimmu.2022.820366. eCollection 2022.
The existence of an amniotic fluid microbiota (i.e., a viable microbial community) in mammals is controversial. Its existence would require a fundamental reconsideration of fetal exposure to and colonization by microorganisms and the role of intra-amniotic microorganisms in fetal immune development as well as in pregnancy outcomes. In this study, we determined whether the amniotic fluid of mice harbors a microbiota in late gestation. The profiles of the amniotic fluids of pups located proximally or distally to the cervix were characterized through quantitative real-time PCR, 16S rRNA gene sequencing, and culture (N = 21 dams). These profiles were compared to those of technical controls for bacterial and DNA contamination. The load of 16S rRNA genes in the amniotic fluid exceeded that in controls. Additionally, the 16S rRNA gene profiles of the amniotic fluid differed from those of controls, with being differentially more abundant in amniotic fluid profiles; however, this bacterium was not cultured from amniotic fluid. Of the 42 attempted bacterial cultures of amniotic fluids, only one yielded bacterial growth - . The 16S rRNA gene of this common murine-associated bacterium was not detected in any amniotic fluid sample, suggesting it did not originate from the amniotic fluid. No differences in the 16S rRNA gene load, 16S rRNA gene profile, or bacterial culture were observed between the amniotic fluids located Proximally and distally to the cervix. Collectively, these data indicate that, although there is a modest DNA signal of bacteria in murine amniotic fluid, there is no evidence that this signal represents a viable microbiota. While this means that amniotic fluid is not a source of microorganisms for colonization in mice, it may nevertheless contribute to fetal exposure to microbial components. The developmental consequences of this observation warrant further investigation.
哺乳动物羊水中是否存在微生物群落（即有活力的微生物群落）存在争议。如果其存在，就需要重新考虑胎儿对微生物的暴露和定植，以及羊水中的微生物在胎儿免疫发育以及妊娠结局中的作用。在这项研究中，我们确定了在妊娠晚期，小鼠的羊水是否存在微生物组。通过定量实时 PCR、16S rRNA 基因测序和培养（N = 21 只孕鼠），对靠近或远离宫颈的胎鼠羊水的特征进行了描述。将这些图谱与细菌和 DNA 污染的技术对照进行了比较。羊水中 16S rRNA 基因的负载量超过了对照。此外，羊水的 16S rRNA 基因图谱与对照不同， 更丰富；然而，该细菌未从羊水培养中分离出来。在对 42 份羊水进行的 42 次细菌培养中，只有一次得到了细菌生长- 。这种常见的与鼠相关的细菌的 16S rRNA 基因在任何羊水样本中均未检测到，表明它不是来自羊水。靠近或远离宫颈的羊水在 16S rRNA 基因负载量、16S rRNA 基因图谱或细菌培养方面没有差异。这些数据表明，尽管在小鼠羊水中存在细菌的 DNA 信号，但没有证据表明该信号代表有活力的微生物组。虽然这意味着羊水不是微生物定植的来源，但它可能仍然会导致胎儿接触微生物成分。这一观察结果的发展后果值得进一步研究。
